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Zandkarimi M, Shafaati A, Foroutan SM, A. Lucy C. Improvement of electrophoretic enantioseparation of amlodipine by polybrene. IRANIAN JOURNAL OF PHARMACEUTICAL RESEARCH : IJPR 2012; 11:129-36. [PMID: 25317194 PMCID: PMC3876563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In chiral and non-chiral electrophoretic resolution of basic drugs, adsorption of analytes to negatively charged capillary wall could lead to poor repeatability of migration time and peak area. In addition, chiral resolutions of basic drugs are commonly performed in low pH buffers. Therefore, longer analysis time due to suppression of electroosmotic flow (EOF) is another dilemma. In this work the improvement effect of polybrene (PB), a cationic polymer, on chiral separation of a model basic drug, amlodipine (AML), was investigated. PB both as a semi-permanent coating agent and as an additive in the running buffer was utilized. Better results were obtained with PB as a buffer additive. Compare to untreated bare silica without using PB in running buffer, addition of 0.0005% PB buffer decreased analysis time downed to 3 folds; efficiency improved up to 5 folds; limit of detection (LOD) and limit of quantification (LOQ) downed to 8 folds and within-day migration time and peak area repeatabilities, in terms of relative standard deviations (RSD) downed to 5 and 20 folds, respectively.
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Paproski RE, Liang C, Lucy CA. High temperature normal phase liquid chromatography of aromatic hydrocarbons on bare zirconia. J Chromatogr A 2011; 1218:7948-55. [DOI: 10.1016/j.chroma.2011.08.087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 08/25/2011] [Accepted: 08/28/2011] [Indexed: 11/29/2022]
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Oro NE, Lucy CA. High performance liquid chromatographic separations of gas oil samples and their hydrotreated products using commercial normal phases. J Chromatogr A 2011; 1218:7788-95. [DOI: 10.1016/j.chroma.2011.08.071] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 08/22/2011] [Accepted: 08/23/2011] [Indexed: 10/17/2022]
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29
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Gulcev MD, Lucy CA. Effect of coating electrolytes on two-tailed surfactant bilayer coatings in capillary electrophoresis. Anal Chim Acta 2011; 690:116-21. [DOI: 10.1016/j.aca.2011.01.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 01/27/2011] [Accepted: 01/27/2011] [Indexed: 11/30/2022]
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Wahab MF, Pohl CA, Lucy CA. Ion chromatography on carbon clad zirconia modified by diazonium chemistry and functionalized latex particles. Analyst 2011; 136:3113-20. [DOI: 10.1039/c1an15284j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Chambers SD, Pohl CA, Lucy CA. Agglomerated carbon based phases for anion exchange chromatography. J Chromatogr A 2011; 1218:263-9. [DOI: 10.1016/j.chroma.2010.11.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 11/09/2010] [Accepted: 11/12/2010] [Indexed: 10/18/2022]
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MacDonald AM, Bahnasy MF, Lucy CA. A modified supported bilayer/diblock polymer – Working towards a tunable coating for capillary electrophoresis. J Chromatogr A 2011; 1218:178-84. [DOI: 10.1016/j.chroma.2010.10.111] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 10/24/2010] [Accepted: 10/26/2010] [Indexed: 10/18/2022]
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Ibrahim MEA, Zhou T, Lucy CA. Agglomerated silica monolithic column for hydrophilic interaction LC. J Sep Sci 2010; 33:773-8. [PMID: 20222075 DOI: 10.1002/jssc.200900698] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hydrophilic interaction LC (HILIC) has gained wide acceptance in recent years due to its ability to retain and separate polar compounds such as pharmaceuticals. Most commercial HILIC phases are particle based, which limit the speed with which HILIC separations can be performed. Herein, agglomerated silica monolithic columns are prepared by electrostatically attaching polyionic latex particles onto a silica monolith by simply flushing a suspension of the ionic latex through a silica monolith. Such phases retain the high efficiency and permeability of the native silica monolith, while the agglomerated phase is easy to introduce and provides excellent mass transfer. High %ACN in the mobile phase dramatically increases the efficiency and retention, consistent with HILIC behavior. Test analytes such as benzoates, nucleotides and amino acids are separated with plate heights of 25-110 microm. The high permeability of monoliths allows HILIC separations to be performed with baseline resolution in less than 15 s. Electrostatic repulsion-hydrophilic liquid interaction chromatographic retention behavior of the latex-coated monoliths is verified using amino acids as test analytes.
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Gulcev MD, McGinitie TM, Bahnasy MF, Lucy CA. Surfactant bilayer coatings in narrow-bore capillaries in capillary electrophoresis. Analyst 2010; 135:2688-93. [DOI: 10.1039/c0an00279h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Chambers SD, McDermott MT, Lucy CA. Covalently modified graphitic carbon-based stationary phases for anion chromatography. Analyst 2009; 134:2273-80. [DOI: 10.1039/b911988d] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Lucy CA, MacDonald AM, Gulcev MD. Non-covalent capillary coatings for protein separations in capillary electrophoresis. J Chromatogr A 2008; 1184:81-105. [DOI: 10.1016/j.chroma.2007.10.114] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Revised: 10/25/2007] [Accepted: 10/31/2007] [Indexed: 11/27/2022]
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37
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Zhou T, Lucy CA. Hydrophilic interaction chromatography of nucleotides and their pathway intermediates on titania. J Chromatogr A 2008; 1187:87-93. [PMID: 18304561 DOI: 10.1016/j.chroma.2008.02.027] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 01/26/2008] [Accepted: 02/04/2008] [Indexed: 11/25/2022]
Abstract
Nucleotides and their pathway intermediates play important roles in all living species. They are essential cellular components in energy transfer, metabolic regulatory processes and biosynthesis. Titania (TiO(2)) has strong Lewis acid sites which have an affinity for the strongly electronegative phosphonate group of nucleotides. Herein a bare titania column (150 mm x 4.6 mm I.D., 3 microm) with UV detection at 254 nm was used for the separation of a set of nucleotides (AMP, ADP, ATP, UMP, UDP, UTP, GMP, GDP, GTP, CMP and CTP) and their intermediates (NAD, NADH, UDP-Glu and UDP-GluNAc). Addition of phosphate to the eluent suppresses the ligand-exchange interactions with the titania surface such that hydrophilic interaction chromatography (HILIC) separations may be performed. Increasing the %ACN resulted in increasing retention and efficiency (up to 13,000, 9500 and 4500 plates/m for AMP, ADP and ATP, respectively). The effects of pH, buffer concentration and other eluent anions (fluoride and acetate) were also studied. Fifteen nucleotides and their intermediates were separated in 26 min (R(minimum)>1.3) using an one-step gradient.
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Gulcev MD, Lucy CA. Factors Affecting the Behavior and Effectiveness of Phospholipid Bilayer Coatings for Capillary Electrophoretic Separations of Basic Proteins. Anal Chem 2008; 80:1806-12. [DOI: 10.1021/ac702408u] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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39
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Glenn KM, Lucy CA. Stability of surfactant coated columns for ion chromatography. Analyst 2008; 133:1581-6. [DOI: 10.1039/b719919h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Chambers SD, Lucy CA. Surfactant coated graphitic carbon based stationary phases for anion-exchange chromatography. J Chromatogr A 2007; 1176:178-84. [DOI: 10.1016/j.chroma.2007.10.108] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 10/24/2007] [Accepted: 10/31/2007] [Indexed: 11/26/2022]
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Chambers SD, Glenn KM, Lucy CA. Developments in ion chromatography using monolithic columns. J Sep Sci 2007; 30:1628-45. [PMID: 17623445 DOI: 10.1002/jssc.200700090] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The focus of this review is on current status and on-going developments in ion chromatography (IC) using monolithic phases. The use and potential of both silica and polymeric monoliths in IC is discussed, with silica monoliths achieving efficiencies upwards of 10(5) plates/m for inorganic ions in a few minutes or less. Ion exchange capacity can be introduced onto the monolithic columns through the addition of ion interaction reagents to the eluent, coating of the monolith with ionic surfactants or polyelectrolyte latexes, and covalent bonding. The majority of the studies to date have used surfactant-coated columns, but the stability of surfactant coatings limits this approach. Applications of monolithic IC columns to the separation of inorganic anions and cations are tabulated. Finally, a discussion on the recent commercialization of monolithic IC columns and the use of monolithic phases for IC peripherals such as preconcentrator columns, microextractors and suppressors is presented.
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Yassine MM, Guo N, Zhong H, Li L, Lucy CA. Off-line coupling of preparative capillary zone electrophoresis with microwave-assisted acid hydrolysis and matrix-assisted laser desorption ionization mass spectrometry for protein sequencing. Anal Chim Acta 2007; 597:41-9. [PMID: 17658311 DOI: 10.1016/j.aca.2007.05.054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 05/25/2007] [Accepted: 05/31/2007] [Indexed: 11/16/2022]
Abstract
An off-line coupling of capillary electrophoresis (CE) with microwave-assisted acid hydrolysis/matrix-assisted laser desorption ionization mass spectrometry (MAAH/MALDI) has been developed for protein identification and characterization. Preparative scale protein separations enable collection of 10-50 pmol of purified cytochrome c for subsequent sequencing using MAAH/MALDI. To reduce protein adsorption onto the silica surface, the cationic surfactant-based coatings, dimethylditetradecylammonium bromide and dimethyldioctadecylammonium bromide, are employed. The choice of the buffer conditions is critical for both the preparative CE and MAAH/MALDI method. The use of high buffer concentrations (100 mM Bis-tris) reduces electromigration dispersion, but suppressed MALDI ionization such that a peptide sequence coverage of only 80% was achieved at a sample loading of 40 g L(-1) of each cytochrome c. By reducing the buffer concentration to 25 mM Bis-tris, the sequence coverage increased to 95% at a sample loading of 40 g L(-1).
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Diress AG, Lucy CA. Self-assembled coating for modification of the electro-osmotic flow in nonaqueous capillary electrophoresis using formamide. CAN J CHEM 2007. [DOI: 10.1139/v07-077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of pure nonaqueous solvents in capillary electrophoresis (CE) can alter the separation selectivity and enhance the solubility of hydrophobic compounds and enables the use of higher voltages. However, control of the electro-osmotic flow (EOF) is essential. In this work, we report the use of self-assembled coatings for EOF modification and elimination of analyte adsorptions onto silica capillaries in pure formamide. Bilayer capillary coatings derived from the double chain cationic surfactant dimethyldioctadecylammonium bromide (2C18DAB) reverses the EOF in buffers such as acetate, formate, and phosphate. Reversed EOF of >1.1 × 10–4 cm2/Vs enables the separation of the pharmaceutical drugs propranolol, metoprolol, chloroquine, and chloropheniramine in less than 5 min with efficiencies of 0.2–0.5 million plates/m (66 000 to 165 000 plates). Chemical and physical factors affecting the coating stability and their influence on separation speed and efficiency of the cationic drugs in formamide are also investigated.Key words: capillary electrophoresis, cationic surfactants, electro-osmotic flow, formamide, nonaqueous solvents.
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Diress AG, Yassine MM, Lucy CA. Semipermanent capillary coatings in mixed organic-water solvents for CE. Electrophoresis 2007; 28:1189-96. [PMID: 17366479 DOI: 10.1002/elps.200600440] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This report describes the creation of semipermanent capillary coatings that are compatible with organic-water solvent systems in CE. The coatings are created by simply rinsing the fused-silica capillary with long double-chain cationic surfactants, such as dimethyl-ditetradecyl ammonium bromide (2C(14)DAB), dihexadecyldimethyl ammonium bromide (2C(16)DAB), and dimethyldioctadecyl ammonium bromide (2C(18)DAB). These surfactants generate semipermanent bilayer coatings on the capillary surface, which display a high degree of stability in buffers containing up to 60% v/v of organic solvents, such as methanol and ACN. The coating stability increases with increasing hydrophobicity of the surfactant, i.e., with increasing chain length. For instance, the EOF changes by only 1.2% in a 2C(18)DAB-coated capillary after 130 capillary volumes of rinsing with 60% v/v methanol containing buffer. The bilayer coatings allow separations to be performed without the need to regenerate the coating between runs or to maintain the EOF modifier in the run buffer. Rapid separations (<2 min) of anions and basic drugs with migration time reproducibility of less than 0.5% RSD and efficiencies of 0.4-0.6 million plates/m are obtained. In addition, selectivity changes for small anions and cationic drugs are also observed when the organic solvent content is adjusted.
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Glenn KM, Lucy CA, Haddad PR. Ion chromatography on a latex-coated silica monolith column. J Chromatogr A 2007; 1155:8-14. [PMID: 17306813 DOI: 10.1016/j.chroma.2007.01.098] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 01/24/2007] [Accepted: 01/26/2007] [Indexed: 11/15/2022]
Abstract
A silica monolith column (Merck Chromolith, 100 mm x 4.6 mm) has been coated with Dionex AS9-SC latex nanoparticles to convert the column into an anion-exchange stationary phase. For comparison purposes, a reversed-phase silica monolith was also converted into an anion-exchange column by coating with the cationic surfactant didodecyldimethylammonium bromide (DDAB). Separations of common inorganic anions were carried out using 7.5 or 5.0 mM 4-hydroxybenzoic acid at pH 7.0 along with suppressed conductivity detection. Direct comparisons were then made between the two columns in terms of selectivity, efficiency and stability. The latex-coated column was on average 50% more efficient than the DDAB-coated column. A 10% decrease in retention times was observed on the DDAB column over 11 h of continuous eluent flow, while the latex coating exhibited <1% change in retention even after 2.5 months of periodic use.
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MacDonald AM, Lucy CA. Highly efficient protein separations in capillary electrophoresis using a supported bilayer/diblock copolymer coating. J Chromatogr A 2006; 1130:265-71. [PMID: 16777117 DOI: 10.1016/j.chroma.2006.05.042] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 05/06/2006] [Accepted: 05/16/2006] [Indexed: 10/24/2022]
Abstract
A surfactant/polymer wall coating consisting of the doubly chained cationic surfactant dimethyldioctadecylammonium bromide (DODAB) and polyoxyethylene (POE) 40 stearate is investigated. The coating is formed by simply rinsing a capillary with a solution containing DODAB and POE 40 stearate. The resultant coating is semi-permanent--demonstrating stable electroosmotic flow (EOF) even after a 60 min high pressure rinse with buffer. The EOF (-0.45+/-(0.23) x 10(-4) cm(2) V(-1) s(-1) at pH 7.4) is suppressed by more than a factor of ten compared to that observed for DODAB alone. Model protein mixtures were separated over a pH range of 3-10 with efficiencies of up to greater than 1 million plates/m for the basic proteins cytochrome c, lysozyme, ribonuclease A and alpha-lactalbumin, and the acidic proteins insulin chain A, trypsin inhibitor, and alpha-chymotrypsinogen A. Migration time reproducibility was 0.5-4.0% from run to run and 0.6-4.3% from day to day. Protein recoveries with this coating ranged from 84% to 97%.
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Pelletier S, Lucy CA. Fast and high-resolution ion chromatography at high pH on short columns packed with 1.8μm surfactant coated silica reverse-phase particles. J Chromatogr A 2006; 1125:189-94. [PMID: 16782112 DOI: 10.1016/j.chroma.2006.05.059] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 05/17/2006] [Accepted: 05/19/2006] [Indexed: 11/16/2022]
Abstract
Rapid ion chromatographic separations of small inorganic anions are performed on columns packed with high-pH resistant Zorbax Extend-C18 1.8 microm silica particles. Seven anions (iodate, chloride, nitrite, bromide, nitrate, phosphate, sulphate) are separated with 1.3 and 2 cm long x 0.46 cm I.D. C18 columns coated with the surfactant didodecyldimethylammonium bromide (DDAB). A 40 s separation is achieved at 2 mL/min with a 2.5 mM 4-hydroxybenzoic acid eluent at pH 10. Finally, the DDAB removal procedure is improved to eliminate the pressure build-up caused by precipitation of the surfactant in the column upon uncoating.
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Yassine MM, Lucy CA. Preparative capillary zone electrophoresis using a dynamic coated wide-bore capillary. Electrophoresis 2006; 27:3066-74. [PMID: 16807937 DOI: 10.1002/elps.200500862] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Preparative capillary zone electrophoresis separations of cytochrome c from bovine and horse heart are performed efficiently in a surfactant-coated capillary. The surfactant, dimethylditetradecylammonium bromide (2C(14)DAB), effectively eliminated protein adsorption from the capillary surface, such that symmetrical peaks with efficiencies of 0.7 million plates/m were observed in 50-microm id capillaries when low concentrations of protein were injected. At protein concentrations greater than 1 g/L, electromigration dispersion became the dominant source of band broadening and the peak shape distorted to triangular fronting. Matching of the mobility of the buffer co-ion to that of the cytochrome c resulted in dramatic improvements in the efficiency and peak shape. Using 100 mM bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane phosphate buffer at pH 7.0 with a 100-microm id capillary, the maximum sample loading capacity in a single run was 160 pmol (2.0 microg) of each protein.
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Pelletier S, Lucy CA. Achieving rapid low-pressure ion chromatography separations on short silica-based monolithic columns. J Chromatogr A 2006; 1118:12-8. [PMID: 16616176 DOI: 10.1016/j.chroma.2006.03.072] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 03/22/2006] [Accepted: 03/22/2006] [Indexed: 11/16/2022]
Abstract
Short silica-based monolithic columns (0.5-1 cm) are coated with the surfactant didodecyldimethylammonium bromide (DDAB) and used for fast ion exchange separations of small inorganic anions. Sources of extra-column band broadening are assessed and minimized to obtain separations of seven analytes (iodate, chloride, nitrate, bromide, nitrite, phosphate, sulphate) in two minutes at 2 mL/min. Eluents used are 6 and 9 mM 4-cyanophenol at pH 7.3-7.4 or 5 mM 4-hydroxybenzoic acid at pH 5.6. DDAB coating stability is improved by 15-fold by the addition of a DDAB coated pre-column before the injection valve. Separations are obtained using a low-pressure glass syringe.
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Harrison CR, Sader JA, Lucy CA. Sulfonium and phosphonium, new ion-pairing agents with unique selectivity towards polarizable anions. J Chromatogr A 2006; 1113:123-9. [PMID: 16488425 DOI: 10.1016/j.chroma.2006.01.132] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 01/26/2006] [Accepted: 01/31/2006] [Indexed: 11/15/2022]
Abstract
Ion-pair chromatography (IPC) almost universally relies upon ammonium-based ion-pairing agents (IPAs) for anion separations. This work compares tetrabutylammonium (TBA) with tetrabutylphosphonium (TBP) and tributylsulfonium (TBS). To best understand the retention behavior analytes used for characterization of the IPAs spanned the Hofmeister series; from kosmotropic monoanions (iodate, chloride, nitrite) and intermediate anions (nitrate, bromide) to chaotropic ions (perchlorate, thiocyanate, iodide). The studies demonstrate that tetrabutylphosphonium is the most chaotropic IPA, followed by tetrabutylammonium and finally tributylsulfonium is the least chaotropic. In the case of the chaotropic anions, the retention of perchlorate was least with tributylsulfonium, and greatest for tetrabutylphosphonium, with tetrabutylammonium being intermediate. The multivalent kosmotropic anions (sulfate, chromate, thiosulfate) demonstrated unique selectivity changes depending on the kosmotropic/chaotropic nature of the IPA. Demonstrating increases in retention with increasing IPA concentration only with tributylsulfonium, whereas the more chaotropic IPAs universally decreased the retention of the multivalent anions.
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