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Patel VD, Shamsi SA, Miller A, Liu A, Powell M. Simultaneous separation and detection of nine kynurenine pathway metabolites by reversed-phase liquid chromatography-mass spectrometry: Quantitation of inflammation in human cerebrospinal fluid and plasma. Anal Chim Acta 2023; 1278:341659. [PMID: 37709424 PMCID: PMC10813655 DOI: 10.1016/j.aca.2023.341659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 07/24/2023] [Accepted: 07/25/2023] [Indexed: 09/16/2023]
Abstract
BACKGROUND The kynurenine pathway (KP) generates eight tryptophan (TRP) metabolites collectively called kynurenines, which have gained enormous interest in clinical research. The importance of KP for different disease states calls for developing a low-cost and high-throughput chromatography-mass spectrometry method to evaluate the potential of different kynurenines. Simultaneous separation of TRP and its eight metabolites is challenging because they have substantial polarity differences (log P = -2.5 to +1.3). RESULTS A low-cost, reversed-phase LC-MS/MS method based on polarity partitioning was established to simultaneously separate and quantitate all nine kynurenine pathway metabolites (KPMs) in a single run for the first time in the open literature. Based on stationary phase screening and ternary mobile phase optimization strategy, high polarity KPMs were retained while medium and low polarity KPMs were eluted in a shorter time. After method validation, we demonstrated the applicability of this LC/MS/MS method by quantitative measurement of all nine KPM in cerebrospinal fluid (CSF) and plasma among two groups of human subjects diagnosed with depression. Furthermore, we measured the differential KPMs in these two groups of low and high inflammation and correlated the results with CRP or TNF-α markers for depression. SIGNIFICANCE Our proposed LC-MS/MS provides a new metabolite assay that can be easily applied in various clinical applications to simultaneously quantify multiple biomarkers in KP dysfunction.
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Affiliation(s)
- Vijay D Patel
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA.
| | - Andrew Miller
- Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, GA, 30322, USA
| | - Aimin Liu
- Department of Chemistry, The University of Texas at San Antonio, San Antonio, TX, 78249, USA
| | - Mark Powell
- Agilent Technologies, Wilmington, DE, 19808, USA
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Patel VD, Shamsi SA, Miller A, Liu A. Quantitation of tryptophan and kynurenine in human plasma using 4-vinylphenylboronic acid column by capillary electrochromatography coupled with mass spectrometry. Electrophoresis 2023; 44:529-539. [PMID: 36718859 PMCID: PMC10129288 DOI: 10.1002/elps.202200251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 01/23/2023] [Accepted: 01/23/2023] [Indexed: 02/01/2023]
Abstract
Tryptophan (TRP) is an essential amino acid catabolized mainly through the kynurenine pathway, and part of it is catabolized in the brain. The abnormal depletion of TRP and production of kynurenine (KYN) by two enzymes, tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), have been linked to various neurological diseases. The ratio of TRP/KYN in plasma is a valuable measure for IDO/TDO activity and the prognosis of disease conditions. The 4-vinylphenylboronic acid (4-VPBA) was evaluated as a novel stationary phase for OT-CEC-MS/MS. TRP, KYN, and 3-hydroxykynurenine were separated using optimum conditions of 15 mM (NH4 )2 CO3 at pH 8 as a background electrolyte and 25 kV separation voltage on a 90 cm column. The usefulness of the 4-VPBA column for simple, fast, repeatable, and sensitive CEC-ESI-MS/MS application was demonstrated for the quantitation of TRP and KYN in the plasma of healthy human subjects and neuroinflammation subjects. The plasma sample was extracted on a zirconia-based ion-exchange cartridge for simultaneous protein precipitation and phospholipid removal. The method of standard addition, in combination with the internal standards approach, was used to prepare the calibration curve to overcome matrix matching and eliminate procedural errors. The developed quantitation method was validated according to FDA guidelines for sensitivity, accuracy, precision, and extraction recovery. The measured plasma level of TRP and KYN in healthy humans is aligned with the human metabolome database for the same two metabolites.
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Affiliation(s)
- Vijay D. Patel
- Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Andrew Miller
- Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, Georgia, USA
| | - Aimin Liu
- Department of Chemistry, The University of Texas at San Antonio, San Antonio, Texas, USA
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Pham U, Alvarado L, Suess GJ, Shamsi SA, Frantz K. Separation of short and medium-chain fatty acids using capillary electrophoresis with indirect photometric detection: Part I: Identification of fatty acids in rat feces. Electrophoresis 2021; 42:1914-1923. [PMID: 34288007 DOI: 10.1002/elps.202100100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 06/29/2021] [Accepted: 07/16/2021] [Indexed: 12/11/2022]
Abstract
Short and medium-chain fatty acids (SMCFAs) are known as essential metabolites found in gut microbiota that function as modulators in the development and progression of many inflammatory conditions as well as in the regulation of cell metabolism. Currently, there are few simple and low-cost analytical methods available for the determination of SMCFA. This report focuses on SMCFA analysis utilizing CE with indirect photometric detection (CE-IPD). A ribonucleotide electrolyte, 5'-adenosine mono-phosphate (5'-AMP), is investigated as an IPD reagent due to its high molar absorptivity and dynamic reserve compatible with separation and detection of SMCFA. The operating parameters like the composition of organic solvent, millimolar concentrations of the complexing agent (alpha-cyclodextrin), 5'-AMP and non-absorbing electrolyte (boric acid), as well as the applied voltage, are optimized for resolution, efficiency, and signal-to-noise ratio. A baseline resolution of all nine SMCFAs is achieved in less than 15 min. Additionally, the developed CE-IPD method shows promising potential to identifying SMCFA in rat fecal supernatant. The presented analytical assay is simple, economical, and has considerably good repeatability. The intraday and interday RSD of less than 1 and 2% for relative migration time, as well as less than 14 and 15% for peak area, respectively, were obtained for SMCFA in fecal solution.
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Affiliation(s)
- Uyen Pham
- Department of Chemistry, Georgia State University, Atlanta, GA, USA
| | - Luis Alvarado
- Department of Chemistry, Georgia State University, Atlanta, GA, USA
| | - Gregory J Suess
- Neuroscience Institute and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA, USA
| | - Kyle Frantz
- Neuroscience Institute and Department of Biology, Georgia State University, Atlanta, GA, USA
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Patel VD, Shamsi SA, Sutherland K. Capillary electromigration techniques coupled to mass spectrometry: Applications to food analysis. Trends Analyt Chem 2021; 139. [DOI: 10.1016/j.trac.2021.116240] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Abstract
Polymeric surfactants (molecular micelles, MoMs) with a variety of chiral head groups and chain lengths may be the most promising chiral selectors when used for sensitive detection of chiral compounds in micellar electrokinetic chromatography-mass spectrometry (MEKC-MS). Various carbohydrate-based MS compatible surfactants with phosphate and sulfate head groups have been recently synthesized in our laboratory for its application in CMEKC-MS. In this chapter, we illustrate that the synthesized glucopyranoside-based MoMs are fully compatible with electrospray ionization MS and can be successfully used as a chiral selector for high-throughput screening of multiple chiral compounds using MRM mode in CMEKC-MS/MS experiments. This chapter describes in detail synthesis and utility of α- and β-glucopyranoside-based polymeric surfactant with two different chain lengths and head groups. The presented examples optimize the effect of appropriate millimolar concentration of monomer sugar surfactants required for polymerization as it affects the separations of acidic and basic compounds. Under the optimized concentration of the monomer needed for polymerization (i.e., an equivalent monomer concentration of MoMs), the superiority of MEKC-MS over MEKC-UV is evident. Structurally similar basic drugs with the difference in hydrophobicity are first tested in MEKC-MS to find the optimum head group and optimum chain length with the aim for developing a widely applicable polymeric glucopyranoside-based surfactant. The partial enantioresolution of several structurally similar basic compounds is significantly improved when switching from one head group to another head group of the glucopyranoside MoMs. Thus, complementary separations using poly-N-β-D-SUGP versus poly-N-β-D-SUGS were seen. This phenomenon also exists when comparing the MoMs, which differ in an anomeric configuration such as poly-N-α-D-SUGP and poly-N-β-D-SUGP.
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Affiliation(s)
- Vijay Patel
- Department of Chemistry, Georgia State University, Natural Science Center, Atlanta, GA, USA
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Natural Science Center, Atlanta, GA, USA.
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Liu Y, Shamsi SA. Chiral Capillary Electrophoresis-Mass Spectrometry: Developments and Applications in the Period 2010-2015: A Review. J Chromatogr Sci 2016; 54:1771-1786. [PMID: 27371855 DOI: 10.1093/chromsci/bmw100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Indexed: 11/14/2022]
Abstract
The sensitive detection of chiral compounds by capillary electrophoresis (CE) in biological samples remains a significant challenge and is currently considered a bottleneck in many chiral analysis projects. Chiral CE-MS can significantly improve the limit of detection and provide high sensitivity compared with chiral CE-UV. Chiral selectors such as modified cyclodextrins (CDs) and polymeric surfactants (a.k.a. molecular micelles, MoMs) in electrokinetic chromatography (EKC), micellar electrokinetic chromatography (MEKC) and capillary electrochromatography (CEC) have been developed to address the need for high sensitivity by CE-MS. However, several problems remain to be investigated to fully understand the potential of these hyphenation modes. This review provides introduction to major chiral CE-MS modes for the novice and highlights the important working principles of each mode of chiral CE-MS. Next, recent practical developments and progress in chiral CE-MS dating from January 2010 to September 2015 are described. The achievements in clinical and biomedical sciences using a variety of chiral selectors such as CDs and MoMs in EKC-MS, MEKC-MS and CEC-MS are discussed. Finally, conclusions and future prospects of CE-MS in chiral analysis are drafted.
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Affiliation(s)
- Yijin Liu
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
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Liu Y, Wu B, Wang P, Shamsi SA. Synthesis, characterization, and application of polysodium N-alkylenyl α-d-glucopyranoside surfactants for micellar electrokinetic chromatography-tandem mass spectrometry. Electrophoresis 2016; 37:913-23. [PMID: 26763089 DOI: 10.1002/elps.201500434] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/05/2015] [Accepted: 12/05/2015] [Indexed: 11/08/2022]
Abstract
Sugar-based ionic surfactants forming micelles are known to suppress ESI of various compounds due to decrease in surface tension upon micelle formation . For the first time, poly (sodium N-undecylenyl-α-d-glucopyranoside 4,6-hydrogen phosphate, (poly-α-d-SUGP) based surfactants with different chain lengths and head groups have been successfully synthesized, characterized, and applied as compatible chiral selector for MEKC-ESI-MS/MS. First, the effect of polymerization concentration of the monomer, α-d-SUGP, was evaluated by enantioseparation of one anionic compound (1,1'-binaphthyl-2,2'diyl-hydrogen phosphate) and one zwitterionic compound (dansylated phenylalanine) in MEKC-UV to find the optimum molar surfactant concentration for polymerization. Next, MEKC-UV and MEKC-MS were compared for the enantioseparation of 1,1'-binaphthyl-2,2'diyl-hydrogen phosphate. The influence of polymeric glucopyranoside based surfactant head groups and carbon chain lengths on chiral Rs was evaluated for two classes of cationic drugs (ephedrine alkaloids and β-blockers). Finally, enantioselective MEKC-MS of ephedrine alkaloids and β-blockers were profiled at their optimum pH 5.0 and 7.0, respectively, using 20 mM NH4 OAc, 25 mM poly-α-d-SUGP at 30 kV and 25°C under optimum spray chamber conditions. The LOD for most of the enantiomers ranges from 10 to 100 ng/mL with S/N of at least ≥3.0.
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Affiliation(s)
- Yijin Liu
- Department of Chemistry, Georgia State University, Atlanta, GA, US
| | - Baolin Wu
- Department of Chemistry, Georgia State University, Atlanta, GA, US
| | - Peng Wang
- Department of Chemistry, Georgia State University, Atlanta, GA, US
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA, US
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Liu Y, Jann M, Vandenberg C, Eap CB, Shamsi SA. Development of an enantioselective assay for simultaneous separation of venlafaxine and O-desmethylvenlafaxine by micellar electrokinetic chromatography-tandem mass spectrometry: Application to the analysis of drug-drug interaction. J Chromatogr A 2015; 1420:119-28. [PMID: 26460073 DOI: 10.1016/j.chroma.2015.09.088] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 09/27/2015] [Accepted: 09/29/2015] [Indexed: 11/30/2022]
Abstract
To-date, there has been no effective chiral capillary electrophoresis-mass spectrometry (CE-MS) method reported for the simultaneous enantioseparation of the antidepressant drug, venlafaxine (VX) and its structurally-similar major metabolite, O-desmethylvenlafaxine (O-DVX). This is mainly due to the difficulty of identifying MS compatible chiral selector, which could provide both high enantioselectivity and sensitive MS detection. In this work, poly-sodium N-undecenoyl-L,L-leucylalaninate (poly-L,L-SULA) was employed as a chiral selector after screening several dipeptide polymeric chiral surfactants. Baseline separation of both O-DVX and VX enantiomers was achieved in 15 min after optimizing the buffer pH, poly-L,L-SULA concentration, nebulizer pressure and separation voltage. Calibration curves in spiked plasma (recoveries higher than 80%) were linear over the concentration range 150-5000 ng/mL for both VX and O-DVX. The limit of detection (LOD) was found to be as low as 30 ng/mL and 21 ng/mL for O-DVX and VX, respectively. This method was successfully applied to measure the plasma concentrations of human volunteers receiving VX or O-DVX orally when co-administered without and with indinivar therapy. The results suggest that micellar electrokinetic chromatography electrospray ionization-tandem mass spectrometry (MEKC-ESI-MS/MS) is an effective low cost alternative technique for the pharmacokinetics and pharmacodynamics studies of both O-DVX and VX enantiomers. The technique has potential to identify drug-drug interaction involving VX and O-DVX enantiomers while administering indinivar therapy.
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Affiliation(s)
- Yijin Liu
- Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - Michael Jann
- Health Science Center, University of North Texas, Fort Worth, TX 76107, United States
| | - Chad Vandenberg
- Midwestern University, Institute for Healthcare Innovation, Glendale, AZ 85308, United States
| | - Chin B Eap
- Unit of Pharmacogenetics and Clinical Psychopharmacology, Department of Psychiatry, Lausanne University, Hospital of Cery, Prilly, Lausanne, Switzerland
| | - Shahab A Shamsi
- Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States.
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Liu Y, Shamsi SA. Combined use of chiral ionic liquid surfactants and neutral cyclodextrins: evaluation of ionic liquid head groups for enantioseparation of neutral compounds in capillary electrophoresis. J Chromatogr A 2014; 1360:296-304. [PMID: 25130088 DOI: 10.1016/j.chroma.2014.07.047] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 07/07/2014] [Accepted: 07/16/2014] [Indexed: 11/15/2022]
Abstract
Cyclodextrins (CDs) are most commonly used chiral selectors in capillary electrophoresis (CE). Although the use of neutral CDs and its derivatives have shown to resolve plethora of charged enantiomers, they cannot resolve neutral enantiomers. The use of ionic liquids (ILs) surfactants forming successful complex with CDs present itself an opportunity to resolve neutral enantiomers. In this work, the effect of IL head groups and their complexation ability with heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) was studied for the separation of neutral enantiomers by CE. First, cationic IL type surfactants with different chiral head groups were synthesized. Physicochemical properties such as critical micelle concentration were determined by surface tension, whereas aggregation and polarity were determined by fluorescence spectroscopy. The complexation ability of ILs with TM-β-CD was characterized in the gas phase by CE-mass spectrometry. The influence of the type of ILs head group and its concentration on chiral resolution, resolution per unit time and selectivity were investigated for four structurally diverse neutral compounds. The binding constants of the neutral analytes to the IL-CD complex were estimated by y-reciprocal method. The hydrophobicity of the side chain of the IL head group displayed significant effect on the binding constants and enantioseparations.
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Affiliation(s)
- Yijin Liu
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - Shahab A Shamsi
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States.
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Bragg W, Shamsi SA. High Throughput Analysis of Chiral Compounds Using Capillary Electrochromatography (CEC) and CEC-Mass Spectrometry with Cellulose Based Stationary Phases. SEP SCI TECHNOL 2013; 48:2589-2599. [PMID: 25264392 DOI: 10.1080/01496395.2012.719984] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To fulfill the ever growing demand for rapid chiral analysis, this research presents an approach for highthroughput enantiomeric separations and sensitive detection of model chiral analytes using capillary electrochromatography (CEC) with UV and MS detection. This was achieved utilizing a short 7 cm CEC columns packed with cellulose tris (3,5-dimethyl-phenylcarbamate) (CDMPC) or sulfonated cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC-SO3) chiral stationary phases (CSPs) applying outlet side injections in CEC-UV. The separation performance was compared between CDMPC and CDMPC-SO3 CSPs for rapid enantio-separation in CEC-UV mode. In addition, using a high sensitivity UV-flow cell in combination with outlet side injections, the S/N and hence the limit of detection of chiral drug could be improved. The 7-cm packed column was also used with traditional inlet injections for CEC coupled to a low-cost single-quadrupole MS. While outlet side injection was not possible in CEC-MS due to instrumentation constraints, the combined use of a short 7 cm column packed with CDMPC-SO3 CSP provided several fold higher throughput. Both CEC-UV and CEC-MS with short packed bed has the potential for a simple, sensitive and cost-effective method for enantiomeric drug profiling in biological samples.
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Affiliation(s)
- William Bragg
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
| | - Shahab A Shamsi
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
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Wang X, Davis I, Liu A, Miller A, Shamsi SA. Improved separation and detection of picolinic acid and quinolinic acid by capillary electrophoresis-mass spectrometry: application to analysis of human cerebrospinal fluid. J Chromatogr A 2013; 1316:147-53. [PMID: 24119749 PMCID: PMC4502419 DOI: 10.1016/j.chroma.2013.09.085] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/27/2013] [Accepted: 09/28/2013] [Indexed: 11/23/2022]
Abstract
"Quinolinic acid (QA)", a metabolite of the kynurenine pathway (KP), is implicated as a major neurological biomarker, which causes inflammatory disorders, whereas there is an increase evidence of the role of picolinic acid (PA) in neuroinflammation. Therefore, there is an urgent need to develop new clinical test for early diagnosis of neuroinflammatory disorders. A comparison is made between three different platforms such as high performance liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS/MS), nano LC-Chip/ESI-MS/MS, as well as the use of cationic (quaternary ammonium) and anionic (sulfonated) coated capillaries in capillary electrophoresis (CE)-ESI-MS/MS. The comparison revealed that CE-ESI-MS/MS method using a quaternary ammonium coated capillary is the best method for analysis of PA and QA. A simple stacking procedure by the inclusion of acetonitrile in the artificial cerebrospinal fluid (CSF) sample was employed to improve the peak shape and sensitivity of KP metabolites in CE-ESI-MS/MS. The developed CE-ESI-MS/MS assay provided high resolution, high specificity and high sensitivity with a total analysis time including sample preparation of nearly 12 min. In addition, excellent intra-day and inter-day repeatability of migration times and peak areas of the metabolites were observed with respective relative standard deviation (RSD) of less than 2.0% and 2.5%. Somewhat broader variations in repeatability for a 3 independently prepared coated capillary (total 35 runs each) with % RSD up to 3.8% and 5.8% was observed for migration time and peak areas, respectively. Artificial CSF was used as a surrogate matrix to simultaneously generate calibration curves over a concentration range of 0.02-10 μM for PA and 0.4-40 μM for QA. The method was then successfully applied to analyze PA and QA in human CSF, demonstrating the potential of this CE-ESI-MS/MS method to accurately quantitate with high specificity and sensitivity.
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Affiliation(s)
- Xiaochun Wang
- Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Ian Davis
- Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Aimin Liu
- Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | | | - Shahab A. Shamsi
- Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
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Lu Y, Shamsi SA. Comparison of positively and negatively charged achiral co-monomers added to cyclodextrin monolith: improved chiral separations in capillary electrochromatography. J Chromatogr Sci 2013; 52:1109-20. [PMID: 24108813 DOI: 10.1093/chromsci/bmt148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Cyclodextrins (CDs) and their derivatives have been one of the most popular and successful chiral additives used in electrokinetic chromatography because of the presence of multiple chiral centers, which leads to multiple chiral interactions. However, there has been relatively less published work on the use of CDs as monolithic media for capillary electrochromatography (CEC). The goal of this study was to show how the addition of achiral co-monomer to a polymerizable CD such as glycidyl methacrylate β-cyclodextrin (GMA/β-CD) can affect the enantioselective separations in monolithic CEC. To achieve this goal, polymeric monoliths columns were prepared by co-polymerizing GMA/β-CD with cationic or anionic achiral co-monomers [(2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and vinyl benzyltrimethyl-ammonium (VBTA)] in the presence of conventional crosslinker (ethylene dimethacrylate) and ternary porogen system including butanediol, propanol and water. A total of 34 negatively charged compounds, 30 positively charged compounds and 33 neutral compounds were screened to compare the enantioresolution capability on the GMA/β-CD, GMA/β-CD-VBTA and GMA/β-CD-AMPS monolithic columns.
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Affiliation(s)
- Yang Lu
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-4098, USA
| | - Shahab A Shamsi
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30302-4098, USA
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Wang X, Davis I, Liu A, Shamsi SA. Development of a CZE-ESI-MS assay with a sulfonated capillary for profiling picolinic acid and quinolinic acid formation in multienzyme system. Electrophoresis 2013; 34:1828-35. [PMID: 23576119 PMCID: PMC4153595 DOI: 10.1002/elps.201200679] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/26/2013] [Accepted: 01/27/2013] [Indexed: 11/08/2022]
Abstract
This article describes the development of a reliable CZE-ESI-MS method to simultaneously separate and quantitate three specific metabolites (3-hydroxyanthranilic acid (3-HAA), quinolinic acid (QA), and picolinic acid (PA)) of the kynurenine pathway (KP) of tryptophan catabolism. Using a covalently bonded sulfonated capillary, the parameters such as pH, type of background electrolyte, type of organic solvent, nebulizer pressure as well as both negative and positive ESI-MS modes were optimized to achieve the best Rs and S/N of three KP metabolites. The developed CZE-ESI-MS assay provided high resolution of PA/QA, high specificity, a total analysis time of 10 min with satisfactory intraday and interday repeatability of migration time and peak areas. Under optimized CZE-ESI-MS conditions, the calibration curves over a concentration range of 19-300 μM for 3-HAA and QA, and 75-300 μM for PA were simultaneously generated. The method was successfully applied for the first time to profile the concentrations of initial substrate, 3-HAA, and its eventual products, PA and QA, formed in the complex multienzyme system. As the ratio of two enzymes, 3-hydroxyanthranilate 3,4-dioxygenase (HAO) and α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) decreases, the concentration of QA approaches essentially zero indicating that all ACMS formed by the action of HAO is consumed by ACMSD rather than its spontaneous decay to QA.
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Affiliation(s)
- Xiaochun Wang
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Ian Davis
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Aimin Liu
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
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He J, Shamsi SA. Application of polymeric surfactants in chiral micellar electrokinetic chromatography (CMEKC) and CMEKC coupled to mass spectrometry. Methods Mol Biol 2013; 970:319-348. [PMID: 23283788 DOI: 10.1007/978-1-62703-263-6_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The use of amino acid-based polymeric surfactants (a.k.a. molecular micelles) in chiral micellar electrokinetic chromatography (CMEKC) has been shown to be a successful separation mode for capillary electrophoresis (CE). In this mode, chiral compounds can be enantioseparated with high efficiency, high chiral selectivity, and versatility. This chapter describes the state-of-the art studies published in the past 5 years in CMEKC using polymeric surfactants. Recent trends in the compatibility of chiral polymeric surfactants with mass spectrometric (MS) detection suggest that this type of chiral selector may be the most promising ones for chiral CE-MS applications. The synthesis of new anionic and cationic MS-compatible polymeric surfactants and their utility in CMEKC and CMEKC-MS are demonstrated. Examples of how to run a typical CMEKC-MS experiment using univariate and multivariate optimization of CMEKC and MS parameters are discussed.
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Affiliation(s)
- Jun He
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
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15
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Abstract
Dietary phytochemicals offer nontoxic therapeutic management as well as chemopreventive intervention for slow-growing prostate cancers. However, the limited success of several single-agent clinical trials suggest a paradigm shift that the health benefits of fruits and vegetables are not ascribable to individual phytochemicals, rather may be ascribed to synergistic interactions among them. We recently reported growth-inhibiting and apoptosis-inducing properties of ginger extract (GE) in in vitro and in vivo prostate cancer models. Nevertheless, the nature of interactions among the constituent ginger biophenolics, viz. 6-gingerol, 8-gingerol, 10-gingerol, and 6-shogoal, remains elusive. Here we show antiproliferative efficacy of the most-active GE biophenolics as single-agents and in binary combinations, and investigate the nature of their interactions using the Chou-Talalay combination index (CI) method. Our data demonstrate that binary combinations of ginger phytochemicals synergistically inhibit proliferation of PC-3 cells with CI values ranging from 0.03 to 0.88. To appreciate synergy among phytochemicals present in GE, the natural abundance of ginger biophenolics was quantitated using LC-UV/MS. Interestingly, combining GE with its constituents (in particular, 6-gingerol) resulted in significant augmentation of GE's antiproliferative activity. These data generate compelling grounds for further preclinical evaluation of GE alone and in combination with individual ginger biophenols for prostate cancer management.
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Affiliation(s)
- Meera Brahmbhatt
- Department of Biology, Georgia State University, Atlanta, GA-30303
| | | | - Ghazia Asif
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA-30322
| | - Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA-30303
| | - Ritu Aneja
- Department of Biology, Georgia State University, Atlanta, GA-30303
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16
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Bragg W, Shamsi SA. A novel positively charged achiral co-monomer for β-cyclodextrin monolithic stationary phase: improved chiral separation of acidic compounds using capillary electrochromatography coupled to mass spectrometry. J Chromatogr A 2012; 1267:144-55. [PMID: 23062876 PMCID: PMC3618962 DOI: 10.1016/j.chroma.2012.08.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/30/2012] [Accepted: 08/01/2012] [Indexed: 11/21/2022]
Abstract
The work presented here demonstrates the incorporation of vinylbenzyl trimethylammonium (VBTA) as a novel positively charged achiral co-monomer to a glycidyl methacrylate-beta cyclodextrin (GMA/β-CD) based monolith, providing anion exchange sites with reversed electroosmotic flow (EOF) for capillary electrochromatography (CEC). The monolithic phases, GMA/β-CD-VBTA and GMA/β-CD (without co-monomer) were characterized by scanning electron microscopy, optical microscopy, pressure drop/flow-rate curves and nitrogen adsorption analysis. After optimizing the stationary phase and mobile phase parameters, chiral separations of 41 pairs of structurally diverse anionic chiral analytes were compared individually using the GMA/β-CD-VBTA and GMA/β-CD monolithic columns. The GMA/β-CD-VBTA monolith chiral stationary phase separated significantly more acidic compounds compared to the GMA/β-CD column. To-date there has been limited work in the development of chiral monolithic column for CEC-mass spectrometry (MS). Because of good electrodriven flow characteristics, which allow the column to maintain a stable current in the absence of outlet vial, GMA/β-CD-VBTA column was successfully coupled to single quadrupole mass spectrometer for CEC-MS of several chiral test compounds. In addition, the same monolithic CEC column when coupled to a triple quadrupole MS instrument, two orders of magnitude higher sensitivity was observed compared to a single quadrupole MS instrument.
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Affiliation(s)
- William Bragg
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
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17
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He J, Wang X, Morill M, Shamsi SA. Amino acid bound surfactants: a new synthetic family of polymeric monoliths opening up possibilities for chiral separations in capillary electrochromatography. Anal Chem 2012; 84:5236-42. [PMID: 22607448 DOI: 10.1021/ac300944z] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
By combining a novel chiral amino-acid surfactant containing an acryloyl amide tail, a carbamate linker, and a leucine headgroup of different chain lengths with a conventional cross-linker and a polymerization technique, a new "one-pot" synthesis for the generation of amino-acid based polymeric monolith is realized. The method promises to open up the discovery of an amino-acid based polymeric monolith for chiral separations in capillary electrochromatography (CEC). The possibility of enhanced chemoselectivity for simultaneous separation of ephedrine and pseudoephedrine containing multiple chiral centers and the potential use of this amino-acid surfactant bound column for CEC and CEC coupled to mass spectrometric detection are demonstrated.
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Affiliation(s)
- Jun He
- Center of Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, Atlanta, Georgia 30303, USA
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18
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Bragg W, Shamsi SA. Development of a fritless packed column for capillary electrochromatography-mass spectrometry. J Chromatogr A 2011; 1218:8691-700. [PMID: 22035695 DOI: 10.1016/j.chroma.2011.09.060] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 09/23/2011] [Accepted: 09/23/2011] [Indexed: 11/25/2022]
Abstract
A novel procedure was developed for the fabrication of a fritless packed column for the coupling of capillary electrochromatography (CEC) to mass spectrometry (MS). The process involved the formation of internal tapers on two separate columns. Once the internal tapers are formed and the columns are packed, the untapered ends of each column were joined together by a commercially available connector. Several advantages of the fritless columns are described. First, the design used here eventually eliminates the need for any frits thus reducing the possibility of bubble formation seen with fritted packed columns. In addition, this is the first report in which the internal tapers are formed at both the inlet and outlet column ends making the fritless CEC-MS column more robust compared to only one report with externally tapered counterparts. Second, a comparison of internally tapered single frit packed CEC-MS (previously developed in our laboratory) column versus fritless CEC-MS column reported here shows that the latter provides better efficiency, suggesting no dead volume with equally good sensitivity and chiral resolution of (±)-aminoglutethimide. The fritless column procedure is universal and was used to prepare a series of columns with a variety of commercially available packing material (mixed mode strong cation exchange, SCX; mixed mode strong anion exchange, SAX; C-18) for the separation and MS detection of short chain non-chromophoric polar amines, long chain nonchromophic anionic surfactant as well as oligomers of non-chromophoric non-ionic surfactants, respectively. The fritless columns showed good intra-day repeatability and inter-day reproducibility of retention times, chiral and achiral resolutions and peak areas. Very satisfactory column-to-column and operator-to-operator reproducibility was demonstrated.
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Affiliation(s)
- William Bragg
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30302, USA
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19
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Gu C, Shamsi SA. Evaluation of a methacrylate-bonded cyclodextrins as a monolithic chiral stationary phase for capillary electrochromatography (CEC)-UV and CEC coupled to mass spectrometry. Electrophoresis 2011; 32:2727-37. [PMID: 21983821 PMCID: PMC3517074 DOI: 10.1002/elps.201000647] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Glycidyl methacrylate-bonded β-cyclodextrin (GMA-β-CD) is synthesized as a new chiral monomer by direct chemical bonding with GMA using a fast and simple alternative procedure. Next, rigid and homogenous monolithic columns were prepared by polymerization of GMA-β-CD monomer with ethylene dimethacrylate (EDMA), in the presence of commonly used porogens and a charged achiral monomer to form a versatile chiral monolith. This is the first report in which a preparation procedure for a methacrylate-bonded CD is introduced for chiral separations in CEC. The degree of substitution of GMA-β-CD monomer and mobile-phase parameters were optimized to achieve the highest enantioselectivity and plate number. To evaluate the GMA-β-CD monolithic column, different classes of chiral compounds were screened. Under the optimized β-CD monolith phase and the optimum mobile-phase conditions, 30 neutral and basic chiral compounds and two acidic compounds could be separated. The high chemical and mechanical stability, homogenous microflow and no loss of material at the interface allows for the first time the feasibility of applying this polymer-based monolithic column for CEC coupled to ESI-MS. Compared with CEC-UV, CEC-ESI-MS showed higher sensitivity and lower resolution. However, resolution greater than 1.0 can still be obtained for majority of the select tested compound in CEC-ESI-MS with at least three out of seven compound providing Rs≥1.5. The results reinforce the potential of GMA-β-CD monolithic columns for chiral separations with high sensitivity in CEC-ESI-MS. Finally, using hexobarbital as the model chiral analyte, the monolithic column demonstrated excellent stability and reproducibility of retention time and enantioselectivity.
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Affiliation(s)
- Congying Gu
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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20
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Karna P, Gundala SR, Gupta MV, Shamsi SA, Pace RD, Yates C, Narayan S, Aneja R. Polyphenol-rich sweet potato greens extract inhibits proliferation and induces apoptosis in prostate cancer cells in vitro and in vivo. Carcinogenesis 2011; 32:1872-80. [PMID: 21948980 DOI: 10.1093/carcin/bgr215] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Sweet potato (Ipomoea batatas) leaves or greens, extensively consumed as a vegetable in Africa and Asia, are an excellent source of dietary polyphenols such as anthocyanins and phenolic acids. Here, we show that sweet potato greens extract (SPGE) has the maximum polyphenol content compared with several commercial vegetables including spinach. The polyphenol-rich SPGE exerts significant antiproliferative activity in a panel of prostate cancer cell lines while sparing normal prostate epithelial cells. Mechanistically, SPGE perturbed cell cycle progression, reduced clonogenic survival, modulated cell cycle and apoptosis regulatory molecules and induced apoptosis in human prostate cancer PC-3 cells both in vitro and in vivo. SPGE-induced apoptosis has a mitochondrially mediated component, which was attenuated by pretreatment with cyclosporin A. We also observed alterations of apoptosis regulatory molecules such as inactivation of Bcl2, upregulation of BAX, cytochrome c release and activation of downstream apoptotic signaling. SPGE caused DNA degradation as evident by terminal deoxynucleotidyl transferase-mediated dUTP-nick-end labeling (TUNEL) staining of increased concentration of 3'-DNA ends. Furthermore, apoptotic induction was caspase dependent as shown by cleavage of caspase substrate, poly (adenosine diphosphate-ribose) polymerase. Oral administration of 400 mg/kg SPGE remarkably inhibited growth and progression of prostate tumor xenografts by ∼69% in nude mice, as shown by tumor volume measurements and non-invasive real-time bioluminescent imaging. Most importantly, SPGE did not cause any detectable toxicity to rapidly dividing normal tissues such as gut and bone marrow. This is the first report to demonstrate the in vitro and in vivo anticancer activity of sweet potato greens in prostate cancer.
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Affiliation(s)
- Prasanthi Karna
- Department of Biology, Georgia State University, Atlanta, GA-30303, USA
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21
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He J, Shamsi SA. Chiral micellar electrokinetic chromatography-atmospheric pressure photoionization of benzoin derivatives using mixed molecular micelles. Electrophoresis 2011; 32:1164-75. [PMID: 21500208 DOI: 10.1002/elps.201000581] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Revised: 01/15/2011] [Accepted: 01/15/2011] [Indexed: 11/08/2022]
Abstract
In the present work we report, for the first time, the successful on-line coupling of chiral MEKC (CMEKC) to atmospheric pressure photoionization MS (APPI-MS). Four structurally similar neutral test solutes (e.g. benzoin (BNZ) derivatives) were successfully ionized by APPI-MS. The mass spectra in the positive ion mode showed that the protonated molecular ions of BNZs are not the most abundant fragment ions. Simultaneous enantioseparation by CMEKC and on-line APPI-MS detection of four photoinitiators, hydrobenzoin, BNZ, benzoin methyl ether, benzoin ethyl ether, were achieved using an optimized molar ratio of mixed molecular micelle of two polymeric chiral surfactants (polysodium N-undecenoxy carbonyl-L-leucinate and polysodium N-undecenoyl-L,L-leucylvalinate). The CMEKC conditions, such as voltage, chiral polymeric surfactant concentration, buffer pH, and BGE concentration, were optimized using a multivariate central composite design (CCD). The sheath liquid composition (involving %v/v methanol, dopant concentration, electrolyte additive concentration, and flow rate) and spray chamber parameters (drying gas flow rate, drying gas temperature, and vaporizer temperature) were also optimized with CCD. Models built based on the CCD results and response surface method were used to analyze the interactions between factors and their effects on the responses. The final overall optimum conditions for CMEKC-APPI-MS were also predicted and found in agreement with the experimentally optimized parameters.
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Affiliation(s)
- Jun He
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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22
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Wang B, He J, Shamsi SA. A high-throughput multivariate optimization for the simultaneous enantioseparation and detection of barbiturates in micellar electrokinetic chromatography-mass spectrometry. J Chromatogr Sci 2010; 48:572-83. [PMID: 20819283 PMCID: PMC3098000 DOI: 10.1093/chromsci/48.7.572] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The R- and S-configurations of barbiturates display differences in potency and biological activity. In this study, multivariate micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) approach for the simultaneous analysis of three chiral barbiturates (mephobarbital, pentobarbital, and secobarbital) is developed using a polymeric chiral surfactant. After screening 11 amino acid polymeric surfactants, polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) was found to be the best chiral selector. The multivariate central composite design (CCD) is used to optimize the chiral resolution, decrease the total analysis time, and improve the ESI-MS signal-to-noise (S/N) ratio. In the preliminary set of experiments, the ranges of the factors investigated in the multivariate approaches are determined. Next, the CCD design is conducted to determine the best overall chiral resolution with shortest possible run times. This optimization resulted in simultaneous enantioseparation in less than 32 min of all three barbiturates with 3-5 fold higher sensitivity by MS compared to UV detection. The adequacy of the multivariate model is validated by three replicate experimental runs at the predicted optimum conditions. The predicted results of MEKC-MS are found to be in good agreement with the experimental data for migration times, resolution, and S/N ratio. The optimized method provided good results in terms of linearity and recovery values of chiral barbiturates spiked in human serum after solid-phase extraction procedure.
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Affiliation(s)
- Bin Wang
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Jun He
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Abstract
A surfactant bound poly (11-acrylaminoundecanoic acid-ethylene dimethacrylate) monolithic column was simply prepared by in situ co-polymerization of 11-acrylaminoundecanoic acid and ethylene dimethacrylate with 1-propanol, 1,4-butanediol and water as porogens in 100 microm id fused-silica capillary in one step. This column was used in CEC-atmospheric pressure photoionization (APPI)-MS system for separation and detection of N-methylcarbamates pesticides. Numerous parameters are optimized for CEC-APPI-MS. After evaluation of the mobile phase composition, sheath liquid composition and the monolithic capillary outlet position, a fractional factorial design was selected as a screening procedure to identify factors of ionization source parameters, such as sheath liquid flow rate, drying gas flow rate, drying gas temperature, nebulizing gas pressure, vaporizer temperature and capillary voltage, which significantly influence APPI-MS sensitivity. A face-centered central composite design was further utilized to optimize the most significant parameters and predict the best sensitivity. Under optimized conditions, S/Ns around 78 were achieved for an injection of 100 ng/mL of each pesticide. Finally, this CEC-APPI-MS method was successfully applied to the analysis of nine N-methylcarbamates in spiked apple juice sample after solid phase extraction with recoveries in the range of 65-109%.
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Affiliation(s)
- Congying Gu
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Abstract
A novel anionic surfactant bound monolithic stationary phase based on 11-acrylaminoundecanoic acid is designed for CEC. The monolith possessing bonded undecanoyl groups (hydrophobic sites) and carboxyl groups (weak cationic ion-exchange sites) were evaluated as a mixed-mode stationary phase in CEC for the separation of neutral and polar solutes. Using a multivariate D-optimal design the composition of the polymerization mixture was modeled and optimized with five alkylbenzenes and seven alkyl phenyl ketones as test solutes. The D-optimal design indicates a strong dependence of electrochromatographic parameters on the concentration of 11-acrylaminoundecanoic acid monomer and porogen (water) in the polymerization mixture. A difference of 6, 8 and 13% RSD between the predicted and the experimental values in terms of efficiency, resolution and retention time, respectively, indeed confirmed that the proposed approach is practical. The physical (i.e. morphology, porosity and permeability) and chromatographic properties of the monolithic columns were thoroughly investigated. With the optimized monolithic column, high efficiency separation of N-methylcarbamates pesticides and positional isomers was successfully achieved. It appears that this type of mixed-mode monolith (containing both chargeable and hydrophobic sites) may have a great potential as a new generation of CEC stationary phase.
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Affiliation(s)
- Congying Gu
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Gu C, He J, Jia J, Fang N, Simmons R, Shamsi SA. Surfactant-bound monolithic columns for separation of proteins in capillary high performance liquid chromatography. J Chromatogr A 2010; 1217:530-9. [PMID: 20031139 PMCID: PMC3098612 DOI: 10.1016/j.chroma.2009.11.082] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 11/25/2009] [Indexed: 10/20/2022]
Abstract
A surfactant-bound monolithic stationary phase based on the co-polymerization of 11-acrylamino-undecanoic acid (AAUA) is designed for capillary high performance liquid chromatography (HPLC). Using D-optimal design, the effect of the polymerization mixture (concentrations of monomer, crosslinker and porogens) on the chromatographic performance (resolution and analysis time) of the AAUA-EDMA monolithic column was evaluated. The polymerization mixture was optimized using three proteins as model test solutes. The D-optimal design indicates a strong dependence of chromatographic parameters on the concentration of porogens (1,4-butanediol and water) in the polymerization mixture. Optimized solutions for fast separation and high resolution separation, respectively, were obtained using the proposed multivariate optimization. Differences less than 6.8% between the predicted and the experimental values in terms of resolution and retention time indeed confirmed that the proposed approach is practical. Using the optimized column, fast separation of proteins could be obtained in 2.5 min, and a tryptic digest of myoglobin was successfully separated on the high resolution column. The physical properties (i.e., morphology, porosity and permeability) of the optimized monolithic column were thoroughly investigated. It appears that this surfactant-bound monolith may have a great potential as a new generation of capillary HPLC stationary phase.
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Affiliation(s)
- Congying Gu
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Jun He
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Jinping Jia
- Department of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Nenghu Fang
- Department of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Robert Simmons
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Abstract
A competitive inhibition mechanism is proposed to investigate the interactions among 2,3,6-tri-O-methyl-beta-CD (TM-beta-CD), cationic ionic liquid type surfactants, N-undecenoxy-carbonyl-L-leucinol bromide (L-UCLB) and profens using affinity CE. The apparent binding constant of TM-beta-CD to L-UCLB was estimated by nonlinear and linear plotting methods. The binding constants of one representative profen (e.g. fenoprofen) to TM-beta-CD and L-UCLB were estimated by a secondary plotting approach. The R- and S-fenoprofens have different binding constant values, resulting in the enantioseparation due to the synergistic effect of the two chiral selectors, TM-beta-CD and L-UCLB.
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Affiliation(s)
- Bin Wang
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Wang B, He J, Bianchi V, Shamsi SA. Combined use of chiral ionic liquid and cyclodextrin for MEKC: Part I. Simultaneous enantioseparation of anionic profens. Electrophoresis 2010; 30:2812-9. [PMID: 19650046 DOI: 10.1002/elps.200800851] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The enantiomers of five profen drugs were simultaneously separated by MEKC with the combined use of 2,3,6-tri-O-methyl-beta-cyclodextrin and chiral cationic ionic liquid, N-undecenoxy-carbonyl-L-leucinol bromide, which formed micelles in aqueous buffers. Enantioseparations of these profen drugs were optimized by varying the chain length and concentration of the IL surfactant using a standard recipe containing 35 mM 2,3,6-tri-O-methyl-beta-cyclodextrin, 5 mM sodium acetate at pH 5.0. The batch-to-batch reproducibility of N-undecenoxy-carbonyl-L-leucinol bromide was tested and found to have no significant impact in terms of enantiomeric resolution, efficiency, and migration time. Finally, this method was successfully applied for the quantitative determination of ibuprofen in pharmaceutical tablets.
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Affiliation(s)
- Bin Wang
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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He J, Shamsi SA. Multivariate approach for the enantioselective analysis in MEKC-MS: II. Optimization of 1,1'-binaphthyl-2,2'-diamine in positive ion mode. J Sep Sci 2009; 32:1916-26. [PMID: 19479771 DOI: 10.1002/jssc.200800711] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Enantiomeric separation and detection of 1,1'-binaphthyl-2,2'-diamine (BNA) has been successfully optimized by MEKC-ESI-MS using a polymeric surfactant polysodium N-undecenoxycarbonyl-L-leucinate (poly-L-SUCL) as a pseudostationary phase. In the first step, MEKC conditions were optimized by a five-factor three-level central composite design (CCD) of experiment. All five MEKC factors (buffer pH, percentage of ACN in the running buffer, concentration of surfactant, concentration of ammonium acetate (NH4OAc), and voltage) were found significant to the responses (measured as the chiral resolution and analysis time). The interactions between MEKC factors were further evaluated using a quadratic model equation which allowed the generation of 3-D response surface image to reach the optimum conditions. To obtain the best S/N, sheath liquid composition and spray chamber parameters were successfully optimized using the same strategy. Baseline enantiomeric resolution in less than 20 min and optimum MS signal of BNA enantiomers (S/N = 45 at 0.4 mg/mL) were ultimately achieved at the optimized conditions. The adequacy of the model was validated by experimental runs at the optimal predicted conditions. The predicted results were found to be in good agreement with the experimental data.
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Affiliation(s)
- Jun He
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Bragg W, Norton D, Shamsi SA. Optimized separation of beta-blockers with multiple chiral centers using capillary electrochromatography-mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 875:304-16. [PMID: 18619928 DOI: 10.1016/j.jchromb.2008.06.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 06/06/2008] [Accepted: 06/17/2008] [Indexed: 10/21/2022]
Abstract
This work focuses on the simultaneous analysis of beta-blockers with multiple stereogenic centers using capillary electrochromatography-mass spectrometry (CEC-MS) with a vancomycin stationary phase. The critical mobile phase variables (composition of organic solvents, acid/base ratios) as well as column temperature and electric field strength, effecting enantioresolution and analysis time were first optimized sequentially. Next, to achieve global optimum a multivariate D-optimal design was used. Although multivariate approach did not improve enantioresolution any further, analysis time was significantly reduced. Under optimum CEC-MS conditions, all stereoisomers were resolved with resolution in the range 1.0-3.1 in less than 60 min with an average signal-to-noise (S/N) greater than 1000. The developed CEC-MS method has the potential to emerge as a screening method for analysis of multiple chiral compounds using a single protocol using the same column and mobile phase conditions, thus reducing the operation time and cost.
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Affiliation(s)
- William Bragg
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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He J, Shamsi SA. Multivariate approach for the enantioselective analysis in micellar electrokinetic chromatography-mass spectrometry. I. Simultaneous optimization of binaphthyl derivatives in negative ion mode. J Chromatogr A 2009; 1216:845-56. [PMID: 19110258 PMCID: PMC2861921 DOI: 10.1016/j.chroma.2008.11.093] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2008] [Revised: 11/10/2008] [Accepted: 11/13/2008] [Indexed: 11/30/2022]
Abstract
A mixture of two molecular micelles polysodium N-undecenoxy carbonyl-L-leucinate, (poly-L-SUCL) and polysodium N-undecanoyl leucylvalinate, (poly-L-SULV) was utilized in micellar electrokinetic chromatography-electrospray ionization-mass spectrometry (MEKC-ESI-MS) to simultaneously separate and detect enantiomers of binaphthyl derivatives. Separation parameters such as background buffer composition, voltage, temperature, and nebulizer pressure were optimized using a multivariate central composite design (CCD). Baseline enantioseparation for both analytes was achieved. The CCD was also used in the optimization of sheath liquid and spray chamber parameters to achieve optimum ESI-MS response. The results demonstrate that CCD is a powerful tool for the optimization of MEKC-MS parameters and the response surface model analysis can provide in-depth statistical understandings of the significant factors required to achieve maximum enantioresolution and ESI-MS sensitivity.
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Affiliation(s)
- Jun He
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, 50 Decatur Street, Atlanta, GA 30303, USA
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Zheng J, Bragg W, Hou J, Lin N, Chandrasekaran S, Shamsi SA. Sulfated and sulfonated polysaccharide as chiral stationary phases for capillary electrochromatography and capillary electrochromatography-mass spectrometry. J Chromatogr A 2009; 1216:857-72. [PMID: 19108837 PMCID: PMC2752677 DOI: 10.1016/j.chroma.2008.11.082] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 11/16/2008] [Accepted: 11/18/2008] [Indexed: 11/21/2022]
Abstract
The applications of polysaccharide phenyl carbamate derivatives as chiral stationary phases (CSPs) for capillary electrochromatography (CEC) are often hindered by longer retention times, especially using a normal-phase (NP) eluent due to very low electroosmotic flow (EOF). Therefore, in this study, we propose an approach for the aforementioned problems by introducing two new types of negatively charged sulfate and sulfonated groups for polysaccharide CSPs. These CSPs were utilized to pack CEC columns for enantioseparation with a NP eluent. Compared to conventional cellulose tris(3,5-dimethylphenyl carbamate) or CDMPC CSPs, the sulfated CDMPC CSP (sulfur content 4.25%, w/w) shortened the analysis time up to 50% but with a significant loss of enantiomeric resolution (approximately 60%). On the other hand, the sulfonated CDMPC CSP (sulfur content 1.76%, w/w) not only provided fast throughput but also maintained excellent resolving power. In addition, its synthesis is much more straightforward than the sulfated one. Furthermore, we studied several stationary phase parameters (CSP loading and silica gel pore size) and mobile phase parameters (including type of mobile phase and its composition) to evaluate the throughput and enantioselectivity. Using the optimized conditions, a chiral pool containing 66 analytes was screened to evaluate the enantioselectivity under three different mobile phase modes (i.e., NP, polar organic phase (POP) and reversed-phase (RP) eluents). Among these mobile phase modes, the RP mode showed the highest success rate, whereas some degree of complementary enantioselectivity was observed with NP and POP. Finally, the feasibility of applying this CSP for CEC-MS enantioseparation using internal tapered column was evaluated with NP, POP and RP eluents. In particular, the NP-CEC-MS provided significantly enhanced sensitivity when methanol was replaced with isopropanol in the sheath liquid. Using aminoglutethimide as model chiral analyte, all three modes of CEC-MS demonstrated excellent durability as well as excellent reproducibility of retention time and enantioselectivity.
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Affiliation(s)
- Jie Zheng
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
- Abbott Laboratories, North Chicago, IL 60064, USA
| | - William Bragg
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Jingguo Hou
- Department of Clinical Sciences and Administration, College of Pharmacy, University of Houston, Texas Medical Center, Houston, TX 77030, USA
| | - Na Lin
- Department of Human Genetics, Division of Medical Genetics, Emory University, Decatur, GA 30033, USA
| | - Sekar Chandrasekaran
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Norton D, Shamsi SA. Packed-column capillary electrochromatography and capillary electrochromatography-mass spectrometry using a lithocholic acid stationary phase. Electrophoresis 2008; 29:2004-15. [PMID: 18425746 DOI: 10.1002/elps.200700460] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The preparation and characterization of a novel lithocholic acid (LCA)-based liquid crystalline (LC) stationary phase (SP) suitable for application in packed-column CEC and CEC coupled to MS is described. The extent of bonding reactions of LCA-SP was assessed using 1H-NMR, 13C-NMR and elemental analysis. This characterization is followed by application of the LCA-SP for separation of beta-blockers, phenylethylamines (PEAs), polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Using the optimum mobile phase operating conditions (pH 3.0-4.5, 10 mM ammonium acetate, 85% v/v ACN), a comparison of the chromatographic ability of the aminopropyl silica phase vs. the LCA-bonded phase was conducted. The results showed improved selectivity for all test analytes using the latter phase. For example, the CEC-MS of beta-blockers demonstrated that the LCA-bonded phase provides separation of six out of seven beta-blockers, whereas the amino silica phase provides four peaks of several co-eluting beta-blockers. For the CEC-MS analysis of PEAs, the LCA-bonded phase showed improved resolution and different selectivity as compared to the aminopropyl phase. An evaluation of the retention trends for PEAs on both phases suggested that the PEAs were retained based on varying degree of hydroxyl substitution on the aromatic ring. In addition, the MS characterization shows several PEAs fragment in the electrospray either by loss of an alkyl group and/or by loss of H2O. Finally, the LCA-bonded phase displayed significantly higher separation selectivity for PAHs and PCBs as compared to the amino silica phase.
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Priego-Capote F, Ye L, Shakil S, Shamsi SA, Nilsson S. Monoclonal behavior of molecularly imprinted polymer nanoparticles in capillary electrochromatography. Anal Chem 2008; 80:2881-7. [PMID: 18336010 DOI: 10.1021/ac070038v] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new approach based on miniemulsion polymerization is demonstrated for synthesis of molecularly imprinted nanoparticles (MIP-NP; 30-150 nm) with "monoclonal" binding behavior. The performance of the MIP nanoparticles is characterized with partial filling capillary electrochromatography, for the analysis of rac-propranolol, where (S)-propranolol is used as a template. In contrast to previous HPLC and CEC methods based on the use of MIPs, there is no apparent tailing for the enantiomer peaks, and baseline separation with 25,000-60,000 plate number is achieved. These effects are attributed to reduction of the MIP site heterogeneity by means of peripheral location of the core cross-linked NP and to MIP-binding sites with the same ordered radial orientation. This new MIP approach is based on the substitution of the functional monomers with a surfactant monomer, sodium N-undecenoyl glycinate (SUG) for improved inclusion in the MIP-NP structure and to the use of a miniemulsion in the MIP-NP synthesis. The feasibility of working primarily with aqueous electrolytes (10 mM phosphate with a 20% acetonitrile at pH 7) is attributable to the micellar character of the MIP-NPs, provided by the inclusion of the SUG monomers in the structure. To our knowledge this is the first example of "monoclonal" MIP-NPs incorporated in CEC separations of drug enantiomers.
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Affiliation(s)
- Feliciano Priego-Capote
- Department of Analytical Chemistry, Córdoba University, Annex C-3 Building, Campus of Rabanales, E-14071 Córdoba, Spain
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Redman AR, Zheng J, Shamsi SA, Huo J, Kelly EJ, Ho RJY, Ritchie DM, Hon YY. Variant CYP2C9 Alleles and Warfarin Concentrations in Patients Receiving Low-Dose Versus Average-Dose Warfarin Therapy. Clin Appl Thromb Hemost 2008; 14:29-37. [PMID: 17895500 DOI: 10.1177/1076029607304403] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This study compared the frequency of variant cytochrome P450 2C9 ( CYP2C9) alleles and warfarin S/R concentration ratio in patients who required low-dose (<2.5 mg/day) and average-dose (5 ± 0.5 mg/day) warfarin. Patients who achieved a therapeutic international normalized ratio were recruited from the Atlanta Veterans Affairs Medical Center anticoagulation clinic. CYP2C9*2 and *3 alleles were determined by validated Taqman allelic discrimination assays. Warfarin S and R concentrations were determined by chiral capillary electrochromatography with electrospray ionization mass spectrometry. At least 1 variant allele was found in 66.7% and 22.2% of patients in the low-dose and average-dose groups, respectively ( P = .001, χ2). The warfarin S/R concentration ratio was 0.665 (range, 0.162-3.58) and 0.452 (range, 0.159-2.36) for patients receiving low-dose and average-dose therapy, respectively ( P = .097). A warfarin requirement of <2.5 mg/day and an elevated warfarin S/R concentration ratio were each associated with a higher frequency of variant CYP2C9 alleles.
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Affiliation(s)
- Andrea R Redman
- Pharmacy Department, Rockdale Medical Center, Conyers, GA 30012, USA.
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Affiliation(s)
- Dean Norton
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303
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Abstract
Ionic liquids (ILs), as separation media, have made significant contributions in the past decades in advancing research in gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). This review, covering reports published from the mid 1980s to early 2007, shows how ILs have been used so far in separation science, originally primarily as GC stationary phases and later as mobile phase additives (both millimolar and major percent levels) for LC and CE. Representative GC and LC chromatograms as well as CE electropherograms are shown. In addition, the very recent findings on the development of ionic liquids with surfactant properties and its applications for chiral and achiral analysis are discussed.
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Affiliation(s)
- Shahab A Shamsi
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA.
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Rizvi SAA, Shamsi SA. Polymeric alkenoxy amino acid surfactants: V. Comparison of carboxylate and sulfate head group polymeric surfactants for enantioseparation in MEKC. Electrophoresis 2007; 28:1762-78. [PMID: 17480038 DOI: 10.1002/elps.200600483] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this work, six amino acid derived (L-leucinol, L-leucine, L-isoleucinol, L-isoleucine, L-valinol, and L-valine) polymeric chiral surfactants with carboxylate and sulfate head groups that were recently synthesized in our laboratory [30, 33, 35] are compared for the simultaneous enantioseparation of several groups of structurally similar analytes under neutral and basic pH conditions. The physicochemical properties of the monomers and polymers of both classes of sulfated and carboxylated surfactants are compared. In addition, cryogenic high-resolution electron microscopy showed tubular structures with distinct order of the tubes of 50-100 nm width. A Plackett-Burmann experimental design is used to study the factors that influence the chiral resolution and analysis time of ten structurally related phenylethylamines (PEAs). It is observed that increasing the number of hydroxy groups on the benzene ring of the PEAs resulted in deterioration of enantioseparation using any of the six polymeric surfactants. For all three classes of PEAs, polysodium N-undecenoxycarbonyl-L-amino acidate (poly-L-SUCAA)-type surfactants provided enhanced resolution compared to that of polysodium N-undecenoxycarbonyl-L-amino acid sulfates (poly-L-SUCAASS). Several classes of basic and neutral chiral compounds (e.g., beta-blockers benzoin derivatives, PTH-amino acids, and benzodiazepines) also provided improved chiral separations with poly-L-SUCAA. Among the poly-L-SUCAAs, polysodium N-undecenoxycarbonyl-L-isoleucine sulfate (poly--SUCL) exhibited overall the best enantioseparation capability for the investigated basic and neutral compounds, while among the poly-L-SUCAASs, polysodium N-undecenoxycarbonyl-L-isoleucine sulfate (poly-L-SUCILS), and polysodium N-undecenoxycarbonyl-L-valine sulfate (poly-L-SUCVS) proved to be equally effective for enantioseparation. This work clearly demonstrates that variation in the head group of polymeric alkenoxy amino acid surfactants has a significant effect on chiral separations.
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Affiliation(s)
- Syed Asad Ali Rizvi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Hou J, Zheng J, Rizvi SAA, Shamsi SA. Simultaneous chiral separation and determination of ephedrine alkaloids by MEKC-ESI-MS using polymeric surfactant I: Method development. Electrophoresis 2007; 28:1352-63. [PMID: 17465416 DOI: 10.1002/elps.200600415] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this work, simultaneous separation of eight stereoisomers of ephedrine and related compounds ((+/-)-ephedrine, (+/-)-pseudoephedrine, (+/-)-norephedrine and (+/-)-N-methylephedrine) was accomplished using a polymeric chiral surfactant, i.e. polysodium N-undecenoxycarbonyl-L-leucinate (poly-L-SUCL) by chiral (C)MEKC-ESI-MS. The conditions of CMEKC were first investigated. The baseline separation of all eight stereoisomers of ephedrine and related compounds was achieved under optimum CMEKC conditions (35 mM poly-L-SUCL, 15 mM NH(4)OAc, pH 6.0, 30% v/v ACN, 30 kV and 20 degrees C) in less than 30 min. Next, a central composite design for response surface modeling has been described to evaluate the electrospray chamber parameters and the sheath liquid conditions. Optimum mass abundance of stereoisomers of ephedrine and related compounds was observed using the spray chamber parameters, namely 250 degrees C drying gas temperature and 8 L/min drying gas flow rate at a nebulizer pressure of 4 psi. Furthermore, the experimental design indicates that the optimum mass abundance of the stereoisomers of ephedrine and related compounds can be obtained using a sheath liquid containing 80:20 v/v methanol-water, 5 mM NH(4)OAc at pH 8.5 delivered at 5 microL/min. Finally, compared to MEKC-UV, the use of poly-L-SUCL in MEKC-MS provided significantly higher sensitivity for stereoisomers of ephedrine and related compounds.
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Affiliation(s)
- Jingguo Hou
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Hou J, Zheng J, Shamsi SA. Simultaneous chiral separation of ephedrine alkaloids by MEKC-ESI-MS using polymeric surfactant II: Application in dietary supplements. Electrophoresis 2007; 28:1426-34. [PMID: 17465418 DOI: 10.1002/elps.200600407] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Chiral MEKC-MS method was utilized for separation, identification, and quantitation of ten enantiomers of ephedrine and related compounds. Enantioselective separations of all ephedrine alkaloids were accomplished through a combination of polysodium N-undecenoxycarbonyl-L-leucinate (poly-L-SUCL) with 30% v/v ACN. Interestingly, the more hydrophilic stereoisomers were eluted later than the hydrophobic ones indicating that hydrogen bonding interactions are much stronger than hydrophobic interactions in the presence of ACN in chiral MEKC. The method was validated in terms of linearity, LOD, LOQ, precision and robustness. The method was finally used in the analysis of three standard reference materials (SRMs). Results of (-)-ephedrine ranged from 12.49 to 0.24 mg/g, for (+)-pseudoephedrine from 4.04 to 0.019 mg/g, for (-)-norephedrine from 0.36 to 0.0031 mg/g, for (+)-norpseudoephedrine from 0.68 to 0.0052 mg/g, for (-)-methylephedrine from 1.18 to 0.0092 mg/g and for (+)-methylpseudoephedrine from 0.086 to 0.00037 mg/g in the SRMs.
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Affiliation(s)
- Jingguo Hou
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA
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Hou J, Zheng J, Shamsi SA. Separation and determination of warfarin enantiomers in human plasma using a novel polymeric surfactant for micellar electrokinetic chromatography-mass spectrometry. J Chromatogr A 2007; 1159:208-16. [PMID: 17499757 PMCID: PMC2748864 DOI: 10.1016/j.chroma.2007.04.037] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Revised: 04/08/2007] [Accepted: 04/19/2007] [Indexed: 11/27/2022]
Abstract
Warfarin is a widely used oral anticoagulant which is mostly administrated as a racemic mixture containing equal amount of R- and S-enantiomers. The two enantiomers are shown to exhibit significant differences in pharmacokinetics and pharmacodynamics. In this study, a new chiral micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) method has been developed using a polymeric chiral surfactant, polysodium N-undecenoyl-L,L-leucyl-valinate (poly-L,L-SULV), as a pseudostationary phase for the chiral separation of (+/-)-warfarin (WAR) and (+/-)-coumachlor (COU, internal standard). Under optimum MEKC-MS conditions, the enantio-separation of both (+/-)-WAR and (+/-)-COU was achieved within 23 min. Calibration curves were linear (R=0.995 for (R)-WAR and R=0.989 for (S)-WAR) over the concentration range 0.25-5.0 microg/mL. The MS detection was found to be superior over the commonly used UV detection in terms of selectivity and sensitivity with LOD as low as 0.1 microg/mL in human plasma. The method was successfully applied to determine WAR enantiomeric ratio in patients' plasma undergoing warfarin therapy.
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Affiliation(s)
| | | | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30303, USA
- Corresponding Author: Professor Shahab A. Shamsi, Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30303, USA, Phone: 404-651-1297; Fax: 404-651-2751,
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Rizvi SAA, Shamsi SA. Synthesis, characterization, and application of chiral ionic liquids and their polymers in micellar electrokinetic chromatography. Anal Chem 2007; 78:7061-9. [PMID: 17007537 PMCID: PMC2526052 DOI: 10.1021/ac060878u] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two amino acid-derived (leucinol and N-methylpyrrolidinol) chiral ionic liquids are synthesized and characterized in both monomeric and polymeric forms. Leucinol-based chiral cationic surfactant is a room-temperature ionic liquid, and pyrrolidinol-based chiral cationic surfactant melts at 30-35 degrees C to form an ionic liquid (IL). The monomeric and polymeric ILs are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation, and partial specific volume. Herein, we present the first enantioseparation using chiral IL as a pseudostationary phase in capillary electrophoresis. Chiral separation of two acidic analytes, (+/-)-alpha-bromophenylacetic acid and (+/-)-2-(2-chlorophenoxy)propanoic acid (+/-)-(2-PPA) can be achieved with both monomers and polymers of undecenoxycarbonyl-L-pryrrolidinol bromide (L-UCPB) and undecenoxycarbonyl-L-leucinol bromide (L-UCLB) at 25 mM surfactant concentration using phosphate buffer at pH 7.50. The chiral recognition seems to be facilitated by the extent of interaction of the acidic analytes with the cationic headgroup of chiral selectors. Polysodium N-undecenoxycarbonyl-L-leucine sulfate (poly-L-SUCLS) and polysodium N-undecenoxycarbonyl-L-leucinate (poly-L-SUCL) were compared at high and low pH for the enantioseparation of (+/-)-(2-PPA). At pH 7.5, poly-L-SUCLS, poly-L-SUCL, and (+/-)-(2-PPA) are negatively charged resulting in no enantioseparation. However, chiral separation was observed for (+/-)-(2-PPA) using poly-L-SUCLS at low pH (pH 2.00) at which the analyte is neutral. The comparison of chiral separation of anionic and cationic surfactants demonstrates that the electrostatic interaction between the acidic analyte and cationic micelle plays a profound role in enantioseparation.
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Affiliation(s)
- Syed Asad Ali Rizvi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303, USA
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Zheng J, Rizvi SAA, Shamsi SA, Hou J. Photopolymerized Sol‐Gel Monolithic Column for Capillary Electrochromatography (CEC) and CEC Coupled to Atmospheric Pressure Photoionization Mass Spectrometry. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070601034238] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Jie Zheng
- a Department of Chemistry , Center of Biotechnology and Drug Design, Georgia State University , Atlanta, Georgia, USA
| | - Syed A. A. Rizvi
- a Department of Chemistry , Center of Biotechnology and Drug Design, Georgia State University , Atlanta, Georgia, USA
| | - Shahab A. Shamsi
- a Department of Chemistry , Center of Biotechnology and Drug Design, Georgia State University , Atlanta, Georgia, USA
| | - Jingguo Hou
- b Department of Clinical Sciences and Administration , College of Pharmacy, University of Houston, Texas Medical Center , Houston, Texas, USA
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Agnew-Heard KA, Shamsi SA, Warner IM. OPTIMIZING ENANTIOSEPARATION OF PHENYLTHIOHYDANTOIN AMINO ACIDS WITH POLYMERIZED SODIUM N-UNDECANOYL L-VALINATE IN CHIRAL ELECTROKINETIC CHROMATOGRAPHY. J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-100100415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
| | - Shahab A. Shamsi
- a Department of Chemistry , Georgia State University , Atlanta , GA , 30303 , U.S.A
| | - Isiah M. Warner
- b Department of Chemistry , Louisiana State University , Baton Rouge , LA , 70803 , U.S.A
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Ali Rizvi SA, Zheng J, Apkarian RP, Dublin SN, Shamsi SA. Polymeric sulfated amino acid surfactants: a class of versatile chiral selectors for micellar electrokinetic chromatography (MEKC) and MEKC-MS. Anal Chem 2007; 79:879-98. [PMID: 17263313 PMCID: PMC2569972 DOI: 10.1021/ac061228t] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work, three amino acid-derived (l-leucinol, l-isoleucinol, l-valinol) sulfated chiral surfactants are synthesized and polymerized. These chiral sulfated surfactants are thoroughly characterized to determine critical micelle concentration, aggregation number, polarity, optical rotation, and partial specific volume. For the first time the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy. The polysodium N-undecenoyl-l-leucine sulfate shows distinct tubular structure, while polysodium N-undecenoyl-l-valine sulfate also shows tubular morphology but without any distinct order of the tubes. On the other hand, polysodium N-undecenoyl-l-isoleucine sulfate (poly-l-SUCILS) displays random distribution of coiled/curved filaments with heavy association of tightly and loosely bound water. All three polymeric sulfated surfactants are compared for enantioseparation of a broad range of structurally diverse racemic compounds at very acidic, neutral, and basic pH conditions in micellar electrokinetic chromatography (MEKC). A small combinatorial library of 10 structurally related phenylethylamines (PEAs) is investigated for chiral separation under acidic and moderately acidic to neutral pH conditions using an experimental design. In contrast to neutral pH conditions, at acidic pH, significantly enhanced chiral resolution is obtained for class I and class II PEAs due to the compact structure of polymeric sulfated surfactants. It is observed that the presence of a hydroxy group on the benzene ring of PEAs resulted in deterioration of enantioseparation. A sensitive MEKC-mass spectrometry (MS) method is developed for one of the PEAs (e.g., (+/-)-pseudoephedrine) in human urine. Very low limit of detection (LOD) is obtained at pH 2.0 (LOD 325 ng/mL), which is approximately 16 times better compared to pH 8.0 (LOD 5.2 microg/mL). Another broad range of chiral analytes (beta-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, benzodiazepinones) studied also provided improved chiral separation at low pH compared to high-pH conditions. Among the three polymeric sulfated surfactants, poly-l-SUCILS with two chiral centers on the polymer head group provided overall higher enantioresolution for the investigated acidic, basic, and neutral compounds. This work clearly demonstrates for the first time the superiority of chiral separation and sensitive MS detection at low pH over conventional high-pH chiral separation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS.
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Affiliation(s)
- Syed Asad Ali Rizvi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30303, USA
| | - Jie Zheng
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30303, USA
| | - Robert P. Apkarian
- Integrated Microscopy and Microanalytical Facility, Emory University, 1515 Pierce Drive, Atlanta, Georgia 30322, USA
| | - Steven N. Dublin
- Integrated Microscopy and Microanalytical Facility, Emory University, 1515 Pierce Drive, Atlanta, Georgia 30322, USA
| | - Shahab A. Shamsi
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30303, USA
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Shamsi SA. Electrokinetic Chromatography: Theory, Instrumentation and Applications Edited by Ute Pyell (University of Marburg, Germany). John Wiley & Sons, Ltd: Chichester. 2006. xii + 540 pp. $235.00. ISBN 0-470-87102-4. J Am Chem Soc 2006. [DOI: 10.1021/ja069790o] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
The CEC-MS of alkyltrimethylammonium (ATMA+) ions with chain lengths ranging from C1-C18 is optimized using an internally tapered column packed with mixed mode reversed phase/strong cation exchange stationary phase. A systematic study of the CEC separation parameters is conducted followed by evaluation of the ESI-MS sheath liquid and spray chamber settings. First, the optimization of CEC separation parameters are performed including the ACN concentration, triethylamine (TEA) content, buffer pH and ammonium acetate concentration. Using 90% v/v ACN with 0.04% v/v TEA as mobile phase, the separation of longer chain C6-C18-TMA+ surfactants could be achieved in 15 min. Lowering the ACN concentration to 70% v/v provided resolution of shorter chain C1, C2-TMA+ from C6-TMA+ although the total analysis time increased to 40 min. Furthermore, variation of both the ACN and TEA content as well as ionic strength has found to significantly influence the retention of longer chain surfactants as compared to shorter chains. The optimum CEC conditions are 70% v/v ACN, 0.04% v/v TEA, pH 3.0 and 15 mM ammonium acetate. Next, the optimization of the ESI-MS sheath liquid composition is conducted comparing methanol to isopropanol followed by the use of experimental design for analysis of spray chamber parameters. Overall, the developed CEC-ESI-MS method allows quantitative and sensitive monitoring of ATMA+ from < or =10 microg/mL down to 10 ng/mL. Utilizing the optimized CEC-ESI-MS protocol, the challenging analysis of commercial sample Arquad S-50 ATMA+ containing cis-trans unsaturated and saturated soyabean fatty acid derivatives is demonstrated.
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Affiliation(s)
- Dean Norton
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30302-4098, USA
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Zheng J, Shamsi SA. Simultaneous enantioseparation and sensitive detection of eight beta-blockers using capillary electrochromatography-electrospray ionization-mass spectrometry. Electrophoresis 2006; 27:2139-51. [PMID: 16645981 DOI: 10.1002/elps.200500874] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The feasibility of using vancomycin chiral stationary phase (CSP) and polar organic eluent is investigated for simultaneous enantioseparation of eight beta-blockers using CEC coupled to ESI mass spectrometric detection (ESI-MS). The internally tapered capillaries were utilized to pack CEC-MS columns. As compared to externally tapered columns, the use of internally tapered columns demonstrated enhanced stability, durability, and reproducibility. A mixture containing methanol/ACN/acetic acid/triethylamine at 70:30:1.6:0.2 v/v/v/v was considered as optimum mobile phase since it provided a good compromise between resolution and analysis time. As expected, sheath liquid and ESI-MS parameters mainly influenced the detection sensitivity. Interestingly, structural information of beta-blockers was available by varying the MS fragmentor voltage using in-house CID in the scan mode. In order to maximize the chiral/achiral resolution, various column-coupling approaches using teicoplanin as complementary CSP to vancomycin were tested. Several changes in the elution order of beta-blockers were observed using multimodal CSPs with some improvement in chiral or achiral resolution. The quantitative aspects of the CEC-MS method were demonstrated using R- and S-talinolol as internal standards. The calibration curves of beta-blockers showed good linearity in the range of 3-600 microM. The enantiomer of beta-blockers at a concentration of 30 nM was detectable. Furthermore, both 0.1 and 1% of the S-enantiomer could be precisely quantified in the presence of 99.9 and 99% of the R-isomer of beta-blocker.
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Affiliation(s)
- Jack Zheng
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, 30302, USA
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Zheng J, Shamsi SA. Capillary Electrochromatography Coupled to Atmospheric Pressure Photoionization Mass Spectrometry for Methylated Benzo[a]pyrene Isomers. Anal Chem 2006; 78:6921-7. [PMID: 17007515 DOI: 10.1021/ac061024c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Benzo[a]pyrene, one of the most carcinogenic PAHs, has 12 monomethylated positional isomers (MBAPs). A strong correlation between the carcinogenicity of these isomers and methyl substitution has been reported. In this study, on-line coupling of capillary electrochromatography (CEC) and atmospheric pressure photoionization mass spectrometry (APPI-MS) provides a unique solution to highly selective separation and sensitive detection of MBAP isomers. The studies indicated that APPI provides significantly better sensitivity compared to electrospray ionization and atmospheric pressure chemical ionization modes of MS. A systematic investigation of APPI-MS detection parameters and CEC separation is established. First, several sheath liquid parameters (including type and concentration of volatile buffers, type and content of organic modifiers, use of dopants and inorganic/organic additives, and sheath liquid flow rate) and APPI-MS spray chamber parameters (capillary voltage, vaporizer temperature, nebulizer pressure) were found to have effects on detection sensitivity as well as the profile of mass spectrum. For example, when ammonium acetate was replaced with acetic acid in the sheath liquid, the MS signal was enhanced as much as 90% and the formation of ammonia adduct was effectively suppressed. Next, the separation of MBAP isomers was conducted on internal tapered columns packed with polymeric C18 stationary phase. With the use of a mobile phase consisting of slightly higher acetonitrile content (90%,v/v) and a small amount of tropylium ion, the analysis times were significantly shortened by 20 min without compromising the resolutions between the isomers. Finally, quantitative aspects of the CEC-APPI-MS method were demonstrated using 7-MBAP as the internal standard. The calibration curves of three of the most carcinogenic isomers, namely, 1-MBAP, 3-MBAP, and 11-MBAP, showed good linearity in the range of 2.5-50 microg/mL with a limit of detection at 400 ng/mL.
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Affiliation(s)
- Jie Zheng
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303, USA
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Affiliation(s)
- Judson L. Haynes
- a Department of Chemistry , Louisiana State University Baton Rouge , LA, 70803
| | - Shahab A. Shamsi
- a Department of Chemistry , Louisiana State University Baton Rouge , LA, 70803
| | - Joykrishna Dey
- a Department of Chemistry , Louisiana State University Baton Rouge , LA, 70803
| | - Isiah M. Warner
- a Department of Chemistry , Louisiana State University Baton Rouge , LA, 70803
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Hou J, Rizvi SAA, Zheng J, Shamsi SA. Application of polymeric surfactants in micellar electrokinetic chromatography-electrospray ionization mass spectrometry of benzodiazepines and benzoxazocine chiral drugs. Electrophoresis 2006; 27:1263-75. [PMID: 16523462 DOI: 10.1002/elps.200500610] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Chiral micellar EKC (CMEKC) coupled to ESI-MS using polymeric surfactants as pseudostationary phases is investigated for simultaneous enantioseparation of two benzodiazepines, (+/-)-oxazepam ((+/-)-OXA) and (+/-)-lorazepam ((+/-)-LOR), and one benzoxazocine, (+/-)-nefopam ((+/-)-NEF). First, enantioselectivity and electrospray sensitivity of six chiral polymeric surfactants for all three chiral compounds are compared. Second, using poly(sodium N-undecenoyl-L-leucinate) as pseudostationary phase, the organic modifiers (methanol (MeOH), isopropanol, and ACN) are added into the running buffer to further improve chiral resolution (RS). Next, a CMEKC-ESI-MS method for the simultaneous enantioseparation of two benzodiazepines is further developed by using a dipeptide polymeric surfactant, poly(sodium N-undecenoxy carbonyl-L,L-leucyl-valinate) (poly-L,L-SUCLV). The CMEKC conditions including nebulizer pressure, capillary length, ammonium acetate concentration, pH, poly-L,L-SUCLV concentration, and capillary temperature were optimized to achieve maximum chiral RS and highest sensitivity of MS detection. The spray chamber parameters (drying gas temperature and drying gas flow rate) as well as sheath liquid conditions (MeOH content, pH, flow rate, and ionic strength) were found to significantly influence MS S/N of both (+/-)-OXA and (+/-)-LOR. Finally, a comparative study between simultaneous UV and MS detection showed high plate numbers, better chiral RS, and enhanced detectability with CMEKC-MS. However, speed of analysis was faster using CMEKC-UV.
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Affiliation(s)
- Jingguo Hou
- Department of Chemistry, Center of Biotechnology and Drug Design, Georgia State University, Atlanta, GA, USA
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