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Pinto EC, Xu C, Cabral LM, Armstrong DW, de Sousa VP. Sensitive detection of topiramate degradation products by high-performance liquid chromatography/electrospray ionization mass spectrometry using ion-pairing reagents and polarity switching. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:116-124. [PMID: 30378202 DOI: 10.1002/rcm.8321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/22/2018] [Accepted: 10/23/2018] [Indexed: 06/08/2023]
Abstract
RATIONALE The chromatographic analysis of topiramate and its degradation products is challenging due to the absence of chromophoric moieties in their structures, the wide polarity range of the compounds and their ionization differences. This work proposes two new mass spectrometry approaches for evaluating these analytes. METHODS Based on the calculated experimental limit of detection (LOD), a highly sensitive high-performance liquid chromatography (HPLC) paired-ion electrospray ionization mass spectrometry (PIESI-MS) method was developed for the determination of topiramate inorganic degradation products. The influence of different solvent systems on the LODs for topiramate and its main degradation products was determined in both positive/negative ionization modes. In addition, a HPLC method to analyze both organic and inorganic degradation products was proposed by mass spectrometry with positive/negative ion switching electrospray ionization. RESULTS A sensitive HPLC/PIESI-MS method was achieved for the efficient separation of topiramate inorganic degradation products. Both sulfate and sulfamate were detected in the positive selected ion monitoring (SIM) mode with an increased sensitivity compared with the negative SIM mode. The HPLC/ESI-MS analysis with positive/negative ion switching allowed the simultaneous separation and detection of the major degradation products of topiramate in a 10-min run using a single column and a single detector. CONCLUSIONS Two new alternative MS approaches for analyzing the main degradation products of topiramate were developed. The proposed methods are considered advantageous over the existing methods and can be applied to quality control studies of topiramate.
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Affiliation(s)
- Eduardo Costa Pinto
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA
| | - Chengdong Xu
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA
| | - Lucio Mendes Cabral
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Daniel W Armstrong
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA
| | - Valéria Pereira de Sousa
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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Sensitive analysis of N-blocked amino acids using high-performance liquid chromatography with paired ion electrospray ionization mass spectrometry. Anal Bioanal Chem 2018; 410:4725-4735. [DOI: 10.1007/s00216-018-0901-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/19/2017] [Accepted: 01/18/2018] [Indexed: 01/03/2023]
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Breitbach ZS, Berthod A, Huang K, Armstrong DW. Mass spectrometric detection of trace anions: The evolution of paired-ion electrospray ionization (PIESI). MASS SPECTROMETRY REVIEWS 2016; 35:201-218. [PMID: 25648413 DOI: 10.1002/mas.21448] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 05/04/2014] [Accepted: 05/04/2014] [Indexed: 06/04/2023]
Abstract
The negative-ion mode of electrospray ionization mass spectrometry (ESI-MS) is intrinsically less sensitive than the positive-ion mode. The detection and quantitation of anions can be performed in positive-ion mode by forming specific ion-pairs during the electrospray process. The paired-ion electrospray ionization (PIESI) method uses specially synthesized multifunctional cations to form positively charged adducts with the anions to be analyzed. The adducts are detected in the positive-ion mode and at higher m/z ratios to produce excellent signal-to-noise ratios and limits of detection that often are orders of magnitude better than those obtained with native anions in the negative-ion mode. This review briefly summarizes the different analytical approaches to detect and separate anions. It focuses on the recently introduced PIESI method to present the most effective dicationic, tricationic, and tetracationic reagents for the detection of singly and multiply charged anions and some zwitterions. The mechanism by which specific structural molecular architectures can have profound effects on signal intensities is also addressed.
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Affiliation(s)
- Zachary S Breitbach
- Department of Chemistry, University of Texas at Arlington, Planetarium Place, Arlington, 76019, Texas
| | - Alain Berthod
- Institute of Analytical Sciences, University of Lyon, 5 rue de la Doua, Villeurbanne, 69100, France
| | - Ke Huang
- Department of Chemistry, University of Texas at Arlington, Planetarium Place, Arlington, 76019, Texas
| | - Daniel W Armstrong
- Department of Chemistry, University of Texas at Arlington, Planetarium Place, Arlington, 76019, Texas
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4
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Reduced matrix effects for anionic compounds with paired ion electrospray ionization mass spectrometry. Anal Chim Acta 2016; 912:74-84. [DOI: 10.1016/j.aca.2016.01.038] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 01/06/2016] [Accepted: 01/17/2016] [Indexed: 11/18/2022]
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Pinto EC, Dolzan MD, Cabral LM, Armstrong DW, de Sousa VP. Topiramate: A Review of Analytical Approaches for the Drug Substance, Its Impurities and Pharmaceutical Formulations. J Chromatogr Sci 2015; 54:280-90. [PMID: 26276847 DOI: 10.1093/chromsci/bmv120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Indexed: 11/14/2022]
Abstract
An important step during the development of high-performance liquid chromatography (HPLC) methods for quantitative analysis of drugs is choosing the appropriate detector. High sensitivity, reproducibility, stability, wide linear range, compatibility with gradient elution, non-destructive detection of the analyte and response unaffected by changes in the temperature/flow are some of the ideal characteristics of a universal HPLC detector. Topiramate is an anticonvulsant drug mainly used for the treatment of different types of seizures and prophylactic treatment of migraine. Different analytical approaches to quantify topiramate by HPLC have been described because of the lack of chromophoric moieties on its structure, such as derivatization with fluorescent moieties and UV-absorbing moieties, conductivity detection, evaporative light scattering detection, refractive index detection, chemiluminescent nitrogen detection and MS detection. Some methods for the determination of topiramate by capillary electrophoresis and gas chromatography have also been published. This systematic review provides a description of the main analytical methods presented in the literature to analyze topiramate in the drug substance and in pharmaceutical formulations. Each of these methods is briefly discussed, especially considering the detector used with HPLC. In addition, this article presents a review of the data available regarding topiramate stability, degradation products and impurities.
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Affiliation(s)
- Eduardo Costa Pinto
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bss, sala 15, Rio de Janeiro 21941-902, Brazil Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA
| | - Maressa Danielli Dolzan
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA Department of Chemistry, Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil
| | - Lucio Mendes Cabral
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bss, sala 15, Rio de Janeiro 21941-902, Brazil
| | - Daniel W Armstrong
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA
| | - Valéria Pereira de Sousa
- Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bss, sala 15, Rio de Janeiro 21941-902, Brazil
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Xu C, Dodbiba E, Padivitage NLT, Breitbach ZS, Armstrong DW. Metal cation detection in positive ion mode electrospray ionization mass spectrometry using a tetracationic salt as a gas-phase ion-pairing agent: evaluation of the effect of chelating agents on detection sensitivity. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:2885-2896. [PMID: 23136019 DOI: 10.1002/rcm.6413] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
RATIONALE The detection of metal cations continues to be essential in many scientific and industrial areas of interest. The most common electrospray ionization mass spectrometry (ESI-MS) approach involves chelating the metal ions and detecting the organometallic complex in the negative ion mode. However, it is well known that negative ion mode ESI-MS is generally less sensitive than the positive ion mode. To achieve greater sensitivity, it is necessary to examine the feasibility of detecting the chelated metal cations in positive ion mode ESI-MS. METHODS Since highly solvated native metal cations have relatively low ionization efficiency in ESI-MS, and can be difficult to detect in the positive ion mode, a tetracationic ion-pairing agent was added to form a complex with the negatively charged metal chelate. The use of the ion-pairing agent leads to the generation of an overall positively charged complex, which can be detected at higher m/z values in the positive ion mode by electrospray ionization linear quadrupole ion trap mass spectrometry. RESULTS Thirteen chelating agents with diverse structures were evaluated in this study. The nature of the chelating agent played as important a role as was previously determined for cationic pairing agents. The detection limits of six metal cations reached sub-picogram levels and significant improvements were observed when compared to negative ion mode detection where the metal-chelates were monitored without adding the ion-pairing reagent (IPR). Also, selective reaction monitoring (SRM) analyses were performed on the ternary complexes, which improved detection limits by one to three orders of magnitude. CONCLUSIONS With this method it was possible to analyze the metal cations in the positive ion mode ESI-MS with the advantage of speed, sensitivity and selectivity. The optimum solution pH for this type of analysis is 5-7. Tandem mass spectrometry (MS/MS) further increases the sensitivity. Speciation is straightforward making this a broadly useful approach for the analysis of metal ions.
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Affiliation(s)
- Chengdong Xu
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019, USA
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Tak V, Purhoit A, Pardasani D, Garg P, Jain R, Dubey DK. Determination of alkyl alkylphosphonic acids by liquid chromatography coupled with electrospray ionization tandem mass spectrometry using a dicationic reagent. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:2637-2648. [PMID: 23059880 DOI: 10.1002/rcm.6384] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A new analytical method based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is proposed and validated for the identification and quantification of alkyl alkylphosphonic acids (AAPAs) in aqueous matrices. Retrospective detection and identification of degradation products of chemical warfare agents is important as an indicator of possible use of chemical warfare agents or of environmental contamination. A commercially available solution of 1,9-nonanediyl-bis-(3-methylimidazolium)bisfluoride (NBMI) allowed detection of AAPAs by positive mode electrospray ionization mass spectrometry by forming an adduct with AAPAs. MS/MS experiments using an ion trap analyzer were carried out for unambiguous identification of AAPAs. Different parameters were optimized in order to obtain both an adequate chromatographic separation and a high sensitivity using experimental design methodology. Quantification was done with matrix-matched calibration standards of AAPAs. The method was validated in terms of linearity (r(2) >0.982), intra- and inter-day precisions (RSD below 15%), and robustness. The method is sensitive enough for the determination of AAPAs in aqueous matrices, with limits of detection in the 1-5 ng mL(-1) range and limits of quantification in the 5-20 ng mL(-1) range. Finally, the method was successfully applied to determine these AAPAs in aqueous samples provided by the Organization for the Prohibition of Chemical Weapons during 26(th) and 29(th) official proficiency tests. The added advantage of this method is identification of low mass range analyte at high mass range, which obviates the background noise at low mass range.
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Affiliation(s)
- Vijay Tak
- Vertox Laboratory, Defence Research and Development Establishment, Gwalior 474002, India
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8
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Dodbiba E, Xu C, Wanigasekara E, Armstrong DW. Sensitive analysis of metal cations in positive ion mode electrospray ionization mass spectrometry using commercial chelating agents and cationic ion-pairing reagents. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:1005-1013. [PMID: 22467449 DOI: 10.1002/rcm.6185] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Metals play a very important role in many scientific and environmental fields, and thus their detection and analysis is of great necessity. A simple and very sensitive method has been developed herein for the detection of metals in positive ion mode ESI-MS. Metal ions are positively charged, and as such they can potentially be detected in positive ion mode ESI-MS; however, their small mass-to-charge (m/z) ratio makes them fall in the low-mass region of the mass spectrum, which has the largest background noise. Therefore, their detection can become extremely difficult. A better and well-known way to detect metals by ESI-MS is by chelating them with complexation agents. In this study eleven different metals, Fe(II), Fe(III), Mg(II), Cu(II), Ru(III), Co(II), Ca(II), Ni(II), Mn(II), Sn(II), and Ag(I), were paired with two commercially available chelating agents: ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS). Since negative ion mode ESI-MS has many disadvantages compared to positive ion mode ESI-MS, it would be very beneficial if these negatively charged complex ions could be detected in the positive mode. Such a method is described in this paper and it is shown to achieve much lower sensitivities. Each of the negatively charged metal complexes is paired with six cationic ion-pairing reagents. The new positively charged ternary complexes are then analyzed by ESI-MS in the positive single ion monitoring (SIM) and single reaction monitoring (SRM) modes. The results clearly revealed that the presence of the cationic reagents significantly improved the sensitivity for these analytes, often by several orders of magnitude. This novel method developed herein for the detection of metals improved the limits of detection (LODs) significantly when compared to negative ion mode ESI-MS and shows great potential in future trace studies of these and many other species.
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Affiliation(s)
- Edra Dodbiba
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019, USA
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Gerardi AR, Lin X, Breitbach ZS, Armstrong DW, Colyer CL. CE-ESI-MS separation of divalent organic and inorganic anions using a tricationic complexing reagent. Electrophoresis 2012; 33:734-40. [DOI: 10.1002/elps.201100405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Alcalde E, Mesquida N, Ibáñez A, Dinarès I. A Halide-for-Anion Swap Using an Anion-Exchange Resin (A- Form) Method: Revisiting Imidazolium-Based Anion Receptors and Sensors. European J Org Chem 2012. [DOI: 10.1002/ejoc.201101355] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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11
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Payagala T, Armstrong DW. Chiral ionic liquids: a compendium of syntheses and applications (2005-2012). Chirality 2011; 24:17-53. [PMID: 22144292 DOI: 10.1002/chir.21975] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 09/30/2011] [Indexed: 11/07/2022]
Abstract
In recent years, the field of chiral ionic liquids (CILs) has undergone exponential growth. As the technology has advanced, new ways of synthesizing stable and structurally diverse ionic liquids have been established. This has led to heretofore unknown applications of CILs as well as in improving efficiency of previously identified applications. In this review article we have compiled a comprehensive database containing structures and physical properties of notable CILs that have been synthesized during the last 6 years. Their applications in the fields of asymmetric organic synthesis, spectroscopy, and chromatography are also illustrated. This is an expansion of our previous review, which covered the literature before 2005.
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Affiliation(s)
- Tharanga Payagala
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019, USA
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Flanigan PM, Brady JJ, Judge EJ, Levis RJ. Determination of Inorganic Improvised Explosive Device Signatures Using Laser Electrospray Mass Spectrometry Detection with Offline Classification. Anal Chem 2011; 83:7115-22. [DOI: 10.1021/ac2014299] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Paul M. Flanigan
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - John J. Brady
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Elizabeth J. Judge
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Robert J. Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, United States
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Dodbiba E, Xu C, Payagala T, Wanigasekara E, Moon MH, Armstrong DW. Use of ion pairing reagents for sensitive detection and separation of phospholipids in the positive ion mode LC-ESI-MS. Analyst 2011; 136:1586-93. [PMID: 21336348 DOI: 10.1039/c0an00848f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Phospholipids make up one of the more important classes of biological molecules. Because of their amphipathic nature and their charge state (e.g., negatively charged or zwitterionic) detection of trace levels of these compounds can be problematic. Electrospray ionization mass spectrometry (ESI-MS) is used in this study to detect very small amounts of these analytes by using the positive ion mode and pairing them with fifteen different cationic ion pairing reagents. The phospholipids used in this analysis were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidic acid (PA), 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), cardiolipin (CA) and sphingosyl phosphoethanolamine (SPE). The analysis of these molecules was carried out in the single ion monitoring (SIM) positive mode. In addition to their detection, a high performance liquid chromatography and mass spectrometry (HPLC-MS) method was developed in which the phospholipids were separated and detected simultaneously within a very short period of time. Separation of phospholipids was developed in the reverse phase mode and in the hydrophilic interaction liquid chromatography (HILIC) mode HPLC. Their differences and impact on the sensitivity of the analytes are compared and discussed further in the paper. With this technique, limits of detection (LODs) were very easily recorded at low ppt (ng L(-1)) levels with many of the cationic ion pairing reagents used in this study.
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Affiliation(s)
- Edra Dodbiba
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019, USA
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Breitbach ZS, Wanigasekara E, Dodbiba E, Schug KA, Armstrong DW. Mechanisms of ESI-MS Selectivity and Sensitivity Enhancements When Detecting Anions in the Positive Mode Using Cationic Pairing Agents. Anal Chem 2010; 82:9066-73. [DOI: 10.1021/ac102115w] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zachary S. Breitbach
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States
| | - Eranda Wanigasekara
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States
| | - Edra Dodbiba
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States
| | - Kevin A. Schug
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States
| | - Daniel W. Armstrong
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, United States
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Dodbiba E, Breitbach ZS, Wanigasekara E, Payagala T, Zhang X, Armstrong DW. Detection of nucleotides in positive-mode electrospray ionization mass spectrometry using multiply-charged cationic ion-pairing reagents. Anal Bioanal Chem 2010; 398:367-76. [PMID: 20652687 DOI: 10.1007/s00216-010-3949-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 06/16/2010] [Accepted: 06/20/2010] [Indexed: 11/30/2022]
Abstract
Nucleotides are a class of molecules that play an essential role in biological systems. A new method has been developed in the detection of nucleotides. These molecules can exist as monomers or constituents of oligomers and polymers. As such, they carry from one to several negative charges. In this study, different cationic ion-pairing reagents were used to complex with each of the 28 nucleotide monomers and nucleotide containing compounds. By using this method, this discrete set of anions was able to be detected in the positive-mode electrospray ionization mass spectrometry, as positively charged complexes. Tandem mass spectrometry experiments were also completed on the ion-pairing reagents that performed the best in the single ion monitoring (SIM) ion mode, and the sensitivity was lowered even further for most of the anions. Limits of detection for compounds such as thymidine diphosphate were improved as much as 100 times compared to the positive SIM mode, and 750 times when compared to the negative mode. A few nucleotides did not show a significant increase in sensitivity when analyzed in the positive ion mode, but in general the new method developed herein resulted in a much greater sensitivity than traditional detection in the negative mode.
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Affiliation(s)
- Edra Dodbiba
- Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX 76019, USA
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Ionic liquids in analytical chemistry. Anal Chim Acta 2010; 661:1-16. [DOI: 10.1016/j.aca.2009.12.007] [Citation(s) in RCA: 587] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 12/04/2009] [Accepted: 12/09/2009] [Indexed: 11/23/2022]
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17
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KrÌÃzÌek T, Breitbach ZS, Armstrong DW, TesarÌová E, Coufal P. Separation of inorganic and small organic anions by CE using phosphonium-based mono- and dicationic reagents. Electrophoresis 2009; 30:3955-63. [DOI: 10.1002/elps.200900416] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Lin X, Gerardi AR, Breitbach ZS, Armstrong DW, Colyer CL. CE-ESI-MS analysis of singly charged inorganic and organic anions using a dicationic reagent as a complexing agent. Electrophoresis 2009; 30:3918-25. [DOI: 10.1002/elps.200900303] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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