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Qian J, Li H, Wang Y, Li Y, Yu J, Zhou L, Pu Q. Zwitterionic surfactant as an additive for efficient electrophoretic separation of easily absorbed rhodamine dyes on plastic microchips. J Chromatogr A 2023; 1688:463716. [PMID: 36565653 DOI: 10.1016/j.chroma.2022.463716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022]
Abstract
Plastic microchips possess the advantages of easy fabrication and low-cost, but their surface properties are frequently incompatible with electrophoretic separation without proper surface modification. Meanwhile, the separation microchannels on typical microchips are usually only a few centimeters long, the pressurized flow may significantly affect the electrophoretic separation if their inner diameters (id) are relatively larger (approximately > 50 μm), viscous separation medium is therefore required for efficient separation. Herein, a zwitterionic surfactant, N-hexadecyl-N,N-dimethyl-3-ammonio-1-propane sulfonate (HDAPS), was used as a multifunctional additive to inhibit the analyte adsorption, improve the surface status, control Joule heating and modulate the resolution on cyclic olefin copolymer microchips with 80 μm id, 5 cm long separation microchannels, eliminating the necessity of viscous polymeric additives. The effectiveness of HDAPS was compared with an ionic polymeric additive, poly(diallydimethylammonium chloride). The streaming potential and electroosmotic flow measurements indicated an effective inhibition of the adsorption of rhodamine B and a stable negative surface charge with zwitterionic HDAPS. Using 15 mmol/L HDAPS, 40% (v/v) methanol, and 10 mmol/L boric acid (pH 3.2) as the running buffer, rapid separation of four rhodamines was achieved within 90 s under a separation electric field of 520 V/cm. The theoretical plate numbers were in a range of 5.0×105-6.9×105/m. The relative standard deviations were no more than 0.9% for retention time and 1.5% for peak area. The proposed system was verified by the determination of rhodamines in eyeshadow and wolfberry, with standard recoveries in a range of 98.2%-101.4%.
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Affiliation(s)
- Jiali Qian
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Hongli Li
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Yuanhang Wang
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Yixuan Li
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Jie Yu
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Lei Zhou
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China.
| | - Qiaosheng Pu
- State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China.
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2
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Sequential Determination of Inorganic Cations and Anions in Cerebrospinal Fluid by Microchip Electrophoresis. Chromatographia 2014. [DOI: 10.1007/s10337-014-2711-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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3
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Troška P, Chudoba R, Danč L, Bodor R, Horčičiak M, Tesařová E, Masár M. Determination of nitrite and nitrate in cerebrospinal fluid by microchip electrophoresis with microsolid phase extraction pre-treatment. J Chromatogr B Analyt Technol Biomed Life Sci 2013; 930:41-7. [DOI: 10.1016/j.jchromb.2013.04.042] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/26/2013] [Accepted: 04/29/2013] [Indexed: 10/26/2022]
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4
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Timerbaev AR. Element speciation analysis using capillary electrophoresis: twenty years of development and applications. Chem Rev 2012; 113:778-812. [PMID: 23057472 DOI: 10.1021/cr300199v] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Andrei R Timerbaev
- Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin Str. 19, 119991 Moscow, Russian Federation.
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5
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Masár M, Bomastyk B, Bodor R, Horčičiak M, Danč L, Troška P, Kuss HM. Determination of chloride, sulfate and nitrate in drinking water by microchip electrophoresis. Mikrochim Acta 2012. [DOI: 10.1007/s00604-012-0788-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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6
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Noblitt SD, Speights RM, Henry CS. Protonated diamines as anion-binding agents and their utility in capillary electrophoresis separations. Electrophoresis 2011; 32:2986-93. [PMID: 22002837 DOI: 10.1002/elps.201100252] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 05/28/2011] [Accepted: 05/28/2011] [Indexed: 11/08/2022]
Abstract
Capillary zone electrophoresis is a proven method for separating small ions because of the inherent charge and differences in mobility of these analytes. Despite its resolving power, CZE can be insufficient for separating ions with similar mobilities. One remedy is to modify mobilities via the addition of background electrolyte complexation agents. However, this approach is not straightforward for inorganic anions, which lack complexation options. To address this shortfall, the diprotonated diamine moiety was investigated for complexation of dianions. Dicationic diamines significantly complexed dianions, and this interaction was not purely electrostatic in nature because affinities varied with dianion identity. Aqueous association constants were measured with affinity capillary electrophoresis (ACE) and found to be similar in magnitude but different in selectivity to those of dianions with magnesium ion. Binding was also investigated for zwitterionic buffers containing the protonated diamine moiety. Zwitterions exhibited binding constants as high as 18 M(-1) (30-mM ionic strength). This work discusses the observed binding constants and their potential usefulness in CZE separations of inorganic anions. Also covered are improvements to ACE methodology and an evaluation of some of the assumptions employed.
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Affiliation(s)
- Scott D Noblitt
- Chemistry Department, Colorado State University, Fort Collins, CO 80523, USA
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7
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Yu H, Ai H, Chen Q. Rapid Analysis of Nitrate and Nitrite by Ion-Interaction Chromatography on a Monolithic Column. Chromatographia 2009. [DOI: 10.1365/s10337-009-1292-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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8
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High-sensitivity microchip electrophoresis determination of inorganic anions and oxalate in atmospheric aerosols with adjustable selectivity and conductivity detection. J Chromatogr A 2009; 1216:1503-10. [DOI: 10.1016/j.chroma.2008.12.084] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 12/21/2008] [Accepted: 12/29/2008] [Indexed: 02/06/2023]
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9
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Wang T, Zhao S, Shen C, Tang J, Wang D. Determination of iodate in table salt by transient isotachophoresis–capillary zone electrophoresis. Food Chem 2009. [DOI: 10.1016/j.foodchem.2008.03.090] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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10
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Threeprom J, Som-Aum W, Lin JM. Separation of the positional isomers of phthalic acids in hydroorganic solvents using capillary electrophoresis. JOURNAL OF ANALYTICAL CHEMISTRY 2007. [DOI: 10.1134/s1061934807120040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Shiddiky MJA, Won MS, Shim YB. Simultaneous analysis of nitrate and nitrite in a microfluidic device with a Cu-complex-modified electrode. Electrophoresis 2006; 27:4545-54. [PMID: 17058308 DOI: 10.1002/elps.200600240] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A CE microsystem coupled with a microchip and a copper-(3-mercaptopropyl) trimethoxysilane (Cu-MPS) complex-modified carbon paste electrode (CPE) was developed for the simultaneous analysis of nitrite and nitrate. The method is based on the electrocatalytic reduction of both analytes with the modified electrode. The Cu-MPS complex was characterized by voltammetric, XPS, and FT-IR analyses. Experimental parameters affecting the sensitivity of the modified electrode were assessed and optimized. The best separation was achieved in a 60 mm separation channel filled with a 20 mM acetate buffer of pH 5.0 containing 3.0 mM CTAB at separation field strength of -250 V/cm within 90 s. The detection potential for the simultaneous analysis of nitrite and nitrate was found to be -225 mV versus Ag/AgCl. A reproducible response (RSD of 3.2% (nitrite) and 2.8% (nitrate), n = 8) for repetitive sample injections reflected the negligible electrode fouling at the modified CPE. The interference effect was examined for other inorganic ions and biological compounds. A wide hydrodynamic range between 0.25 and 120 microM was observed for analyzing nitrite and nitrate with the sensitivities of 0.069 +/- 0.003 and 0.065 +/- 0.002 nA/microM, and the detection limits, based on S/N = 3, were found to be 0.09 +/- 0.007 and 0.08 +/- 0.009 microM, respectively. The applicability of the method to water and urine samples analyses was demonstrated.
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Affiliation(s)
- Muhammad J A Shiddiky
- Department of Chemistry and Center for Innovative BioPhysio Sensor Technology, Pusan National University, Busan, South Korea
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Kaneta T, Ueda T, Hata K, Imasaka T. Suppression of electroosmotic flow and its application to determination of electrophoretic mobilities in a poly(vinylpyrrolidone)-coated capillary. J Chromatogr A 2006; 1106:52-5. [PMID: 16443452 DOI: 10.1016/j.chroma.2005.08.062] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2005] [Revised: 08/19/2005] [Accepted: 08/22/2005] [Indexed: 11/23/2022]
Abstract
A hydrophilic polymer, poly(vinylpyrrolidone) (PVP), was employed for suppressing the electroosmotic flow (EOF). A capillary was filled with aqueous PVP solution for coating the capillary wall with PVP; the PVP solution was then replaced by a migration buffer solution containing no PVP. Three types of PVP with different molecular weights were examined. The EOF was suppressed more effectively as the molecular weight of PVP increased. The EOF in the coated capillary was approximately 10-fold smaller than that of a bare capillary and was constant in the pH range of 6-8. The suppressed EOF was stable even when no PVP was added to the migration buffer. However, the EOF increased significantly when sodium dodecyl sulfate was added into the migration buffer. The method was applied for determining the electrophoretic mobilities of inorganic anions that have negative electrophoretic mobilities larger than the electroosmotic mobility of the bare capillary. A novel method for determining the electrophoretic mobilities was proposed based on the linear relationship between electric current and electrophoretic mobility. The electrophoretic mobility was proportional to the electric current. Therefore, the intercept of the regression equation represents the electrophoretic mobility at room temperature. The electrophoretic mobilities were in good agreement with the absolute electrophoretic mobilities.
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Affiliation(s)
- Takashi Kaneta
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan
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13
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Diress AG, Lucy CA. Study of the selectivity of inorganic anions in hydro-organic solvents using indirect capillary electrophoresis. J Chromatogr A 2005; 1085:155-63. [PMID: 16106863 DOI: 10.1016/j.chroma.2004.12.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In capillary electrophoresis (CE) analysis of small inorganic anions, the ability to control the electroosmotic flow (EOF) and the ability to alter the electrophoretic mobility of the ions are essential to improve resolution and separation speed. In this work, a CE method for separation of small inorganic anions using indirect detection in mixed methanol/water buffers is presented. The suitability of different UV absorbing probes commonly used for indirect detection including chromate, iodide, phthalate, benzoate, trimellitate, and pyromellitate, in mixed methanol/water buffers is examined. The effect of the electrolyte buffer system, including the pH, buffer concentration and the organic solvent on the electrophoretic mobility of the probes and analytes are also investigated. The EOF was reversed using cationic surfactant, cetyltrimethylammonium bromide (CTAB) so ions were separated under co-EOF mode. The organic solvent alters the electrophoretic mobility of the probes and the analytes differently and hence choice of the appropriate probe is essential to achieve high degree of detection sensitivity. Separations of six anions in less than 2.5 min were accomplished in buffers containing up to 30% MeOH. Adjustment of the methanol content helps to improve the selectivity and resolution of inorganic anions. Limit of detection, reproducibility and application of the method for quantification of anions in water samples will also be discussed.
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Affiliation(s)
- Abebaw G Diress
- Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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Wei W, Ju H. Application of dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium in wall modification for capillary electrophoresis separation of proteins. Electrophoresis 2005; 26:586-92. [PMID: 15690431 DOI: 10.1002/elps.200410273] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A zwitterionic surfactant, dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium (C12H25N+(CH3)2CH2CHOHCH2SO3-), named dodecyl sulfobetaine (DSB), was used as a novel modifier to coat dynamically capillary walls for capillary electrophoresis separation of basic proteins. The DSB coating suppressed the electroosmotic flow (EOF) in the pH range of 3-12. At high DSB concentration, the EOF was suppressed by more than 8.8 times. The DSB coating also prevented successfully the adsorption of cationic proteins on the capillary wall. Anions, such as Cl-, Br-, I-, SO4(2-), CO3(2-), and ClO4-, could be used as running buffer modifiers to adjust the EOF for better separation of analytes. Using this dynamically coated capillary, a mixture of eight inorganic anions achieved complete separation within 4.2 min with the efficiencies from 24,000 to 1,310,000 plates/m. In the presence of ClO4- as EOF adjustor, the separation of a mixture containing four basic proteins (lysozyme, cytochrome c, alpha-chymotrypsinogen A, and myoglobin) yielded efficiencies of 204,000-896,000 plates/m and recoveries of 88%-98%. Migration time reproducibility of these proteins was less than 0.5% relative standard deviation (RSD) from run to run and less than 3.1% RSD from day to day, showing promising application of this novel modifier in protein separation.
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Affiliation(s)
- Wei Wei
- Key Laboratory of Analytical Chemistry for Life Science, Education Ministry of China, Department of Chemistry, Nanjing University, Nanjing, P.R. China
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15
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YOKOYAMA T, ZENKI M, MACKA M, HADDAD PR. Enhancement of Separation Capability of Inorganic Ions by Capillary Electrochromatography. BUNSEKI KAGAKU 2005. [DOI: 10.2116/bunsekikagaku.54.107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Takashi YOKOYAMA
- Department of Chemistry, Faculty of Science, Okayama University of Science
| | - Michio ZENKI
- Department of Chemistry, Faculty of Science, Okayama University of Science
| | - Miroslav MACKA
- Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania
| | - Paul R. HADDAD
- Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania
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16
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Prest JE, Baldock SJ, Fielden PR, Goddard NJ, Treves Brown BJ. Analysis of chloride, bromide and iodide using miniaturised isotachophoresis on a planar polymer chip. Analyst 2005; 130:1375-82. [PMID: 16172662 DOI: 10.1039/b507978k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new method has been developed to allow the determination of the halide anions chloride, bromide and iodide using isotachophoresis. This method employs a new electrolyte system which incorporates the novel application of indium(III) as a complexing agent. This electrolyte system was devised based on the findings of an investigation into the potential for using indium(III) as a complexing counter ion to selectively manipulate the effective mobilities of halide ions. A leading electrolyte incorporating 3.5 mmol dm(-3) of indium(III) allowed the simultaneous determination of chloride, bromide and iodide to be successfully achieved. The new procedure allows such separations to be made without interference from common inorganic anions such as sulfate and nitrate. Separations were performed using a miniaturised planar poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes. Using this instrumentation the limits of detection were calculated to be 0.7 mg dm(-3), 1.7 mg dm(-3) and 2.2 mg dm(-3) for chloride, bromide and iodide respectively.
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Affiliation(s)
- Jeff E Prest
- School of Chemical Engineering and Analytical Science, The University of Manchester, PO Box 88, Manchester, UK M60 1QD.
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Yokota K, Fukushi K, Takeda S, Wakida SI. Simultaneous determination of iodide and iodate in seawater by transient isotachophoresis–capillary zone electrophoresis with artificial seawater as the background electrolyte. J Chromatogr A 2004; 1035:145-50. [PMID: 15117084 DOI: 10.1016/j.chroma.2004.02.041] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We developed capillary zone electrophoresis with transient isotachophoresis (ITP) as an on-line concentration procedure for simultaneous determination of iodide and iodate in seawater. The effective mobility of iodide was decreased by addition of 20 mM cetyltrimethylammonium chloride to an artificial seawater background electrolyte so that transient ITP functioned for both iodide and iodate. Limits of detection for iodide and iodate were 4.0 and 5.0 microg/l (as iodine) at a signal-to-noise ratio of 3. Values of the relative standard deviation of peak area, peak height, and migration times for iodide and iodate were 2.9, 1.3, 1.0 and 2.3, 2.1, 1.0%, respectively. The proposed method was applied to simultaneous determination of iodide and iodate in seawater collected at a pond at our university.
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Affiliation(s)
- Kuriko Yokota
- Research Institute for Marine Cargo Transportation, Kobe University of Mercantile Marine, 5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe 658-0022, Japan
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Martínez V, García N, Antigüedad I, Alonso RM, Jiménez RM. Capillary electrophoresis as a useful tool for the analysis of chemical tracers applied to hydrological systems. J Chromatogr A 2004; 1032:237-42. [PMID: 15065801 DOI: 10.1016/j.chroma.2003.11.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A capillary electrophoretic method was optimised for the separation and determination of iodide used as artificial tracer in hydrology. The influence of the buffer concentration and pH, electroosmotic flow modifier concentration (cetyltrimethylammonium bromide (CTAB)), the injection time and voltage applied, on the electrophoretic separation was studied. A running buffer of 20 mM phosphate (pH 8) containing 1 mM CTAB was found to provide the optimum separation of iodide with respect to resolution, migration time and selectivity. The water samples were injected hydrostatically at 10 cm for 110 s, the voltage applied was -20 kV and a detection wavelength of 214 nm. The influence of the sulphite added to water samples in order to prevent the oxidation of iodide to iodate was also studied. This method can be applied to the determination of iodide free of sulphite interference up to at least a ratio of 1:1000 (I(-):SO3(2-)). The other inorganic anions, which are present in the water samples (mainly chloride, sulphate, nitrate, carbonate), do not interfere with the determination of iodide. This method allows the simultaneous determination of bromide, nitrite, and nitrate together with iodide. The electrophoretic method showed to be linear from 0.5 to 5 mg l(-1) of iodide (the migration time was 2.6 min) with a quantitation limit of 0.45 mg l(-1) and a intraday repeatability lower than 4% of R.S.D. at different concentration levels.
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Affiliation(s)
- V Martínez
- Departamento de Química Analítica, Facultad de Ciencias, Universidad del País Vasco/EHU, Apdo. 664, 48080 Bilbao, Spain
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Diress AG, Lucy CA. Electroosmotic flow reversal for the determination of inorganic anions by capillary electrophoresis with methanol–water buffers. J Chromatogr A 2004; 1027:185-91. [PMID: 14971502 DOI: 10.1016/j.chroma.2003.10.081] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Manipulation of the electroosmotic flow (EOF) is essential for achieving optimized separations of small anions by capillary electrophoresis (CE). In this work, efficient suppression or reversal of EOF is achieved upon addition of small amounts of the cationic surfactants, cetyltrimethylammonium bromide (CTAB) or didodecyldimethylammonium bromide (DDAB) to the electrophoretic buffer. Highly stable and reversed EOF are achieved using the surfactants in the presence of up to 50% MeOH. In aqueous and low methanol containing solutions (up to 30%, v/v) surface aggregation of the surfactants at the capillary wall occurs at a concentration below the critical micelle concentration (CMC). The impact of MeOH on reversed EOF is predominantly a function of the diminished zeta potential of the silica, and to a lesser extent on the CMC in the bulk solution of the surfactant. Fast baseline separation and selectivity changes for small inorganic anions are observed when mixed aqueous-organic buffers are employed. Changes in EOF, micellar properties of the surfactant and selectivity for inorganic anions upon addition of various percent of methanol are also discussed.
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Affiliation(s)
- Abebaw G Diress
- Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alta., T6G 2G2 Canada
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Jiang W, Awasum JN, Irgum K. Control of electroosmotic flow and wall interactions in capillary electrophoresis capillaries by photografted zwitterionic polymer surface layers. Anal Chem 2003; 75:2768-74. [PMID: 12948148 DOI: 10.1021/ac020665e] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel capillary with covalently bonded zwitterionic surface modification was prepared by photograft polymerization of the zwitterionic monomer N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine, onto the inner surface of a UV-transparent fused-silica capillary. Although the zwitterionic moieties in the resulting polymeric "tentacles" comprise both a positive quaternary ammonium group and a negative sulfonate group, the coating has a net zero charge. The electroosmotic flow (EOF) was therefore extensively suppressed on the grafted capillary compared to the native silica capillary and to the silica capillary that had been activated for graft polymerization by reaction with 3-(methacryloyl)oxypropyltrimethoxysilane. It was also found that the EOF can be varied by adding chaotropic anions or divalent cations such as perchlorate ion and magnesium ion to the running buffer, due to the interaction between these ions and zwitterionic functional group. This provides a new way of altering the EOF and the wall interaction without changing the pH or the overall ionic strength of the separation buffer. The influence of pH and ionic strength of separation buffer on the EOF were also investigated to optimize the separation conditions. Good separations of a mixture containing eight inorganic anions were achieved within 5 min under optimal conditions by capillary zone electrophoresis. The newly prepared capillary was also well suited for the separation of peptides or proteins.
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Affiliation(s)
- Wen Jiang
- Department of Analytical Chemistry, Umeå University, S-90198 Umeå, Sweden
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Abstract
Despite the availability of commercial capillary electrophoresis systems for over ten years, where quantitative analysis is required, capillary zone electrophoresis (CZE) has often failed to replace ion chromatography as the method of choice for a large number of analytes, not least inorganic anions. To investigate the reasons for this apparent failing, a review is presented of work that has been carried out to-date involving the quantitative application of CZE to the determination of inorganic anions in industrial and environmental samples. This review summarizes work both investigating and improving the quantitative aspects of the CZE of inorganic anions. A complete survey of how CZE has been applied to the determination of inorganic anions in real samples is given, including what, if any, analytical performance parameters were investigated and quoted, and if quality assurance data and validation methods were briefly considered, thoroughly investigated or simply ignored.
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Affiliation(s)
- Brett Paull
- National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin, Ireland.
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Danková M, Strasík S, Kaniansky D. Determination of orotic acid in urine by capillary zone electrophoresis in tandem-coupled columns with diode array detection. J Chromatogr A 2003; 990:121-32. [PMID: 12685590 DOI: 10.1016/s0021-9673(02)01810-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Analytical potentialities of capillary zone electrophoresis in the separation system with tandem-coupled columns to the spectral identification and determination of orotic acid (OA) in urine by diode array detection (DAD), coupled to the separation system via optical fibers, were investigated. A very significant "in-column" clean-up of OA from urine matrix was reached in the separation stage of the tandem by combining a low pH (2.8) with complexing effects of electroneutral agents [alpha- and beta-cyclodextrins, poly(vinylpyrrolidone) and 3-(N,N-dimethyldodecylammonio)propanesulfonate]. Due to this, its DAD spectral data could be acquired in the detection stage of the tandem with almost no disturbances by matrix co-migrants. The concentration limits of detection obtained under such working conditions for a 200-nl sample load of OA and 320 microm I.D. capillary tubes were 3.5 micromol/l (218 nm) and 0.4 micromol/l (280 nm). Using chemometry procedures (target transformation factor analysis, fixed size moving window-evolving factor analysis, orthogonal projection approach and fixed size moving window-target transformation factor analysis) in processing of the acquired spectral data, the presence of OA in the loaded urine matrix could be confirmed with confidence when its concentration was 10 micromol/l or slightly less.
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Affiliation(s)
- Mariana Danková
- Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská Dolina CH-2, SK-84215 Bratislava, Slovak Republic
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Kikura-Hanajiri R, Martin RS, Lunte SM. Indirect measurement of nitric oxide production by monitoring nitrate and nitrite using microchip electrophoresis with electrochemical detection. Anal Chem 2002; 74:6370-7. [PMID: 12510761 DOI: 10.1021/ac0204000] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An indirect method for monitoring nitric oxide (NO) by determining nitrate and nitrite using microchip capillary electrophoresis (CE) with electrochemical (EC) detection has been developed. This method combines determination of nitrite by direct amperometric detection following a microchip-based CE separation and conversion of nitrate to nitrite by chemical reduction using Cu-coated Cd granules. The amount of nitrate is quantified by calculating the difference in the amount of nitrite in the sample before and after the reduction of nitrate. Optimization of the separation, injection, detection, and reduction reaction conditions, as well as studies involving integration of the reduction reaction onto the microchip, are described. It was found that nitrite can be separated and detected in approximately 45 s by microchip CEEC. The reduction reaction was successfully integrated on-chip and carried out in approximately 1 min following activation of the Cd granules. The usefulness of this device was demonstrated by monitoring the amount of nitrate and nitrite produced from 3-morpholinosydnonimine, a NO-releasing compound.
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Affiliation(s)
- Ruri Kikura-Hanajiri
- Division of Pharmacognosy, Phytochemistry and Narcotics, National Institute of Health Sciences, Tokyo, Japan
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Tu C, Lee HK. Determination of nitrate in seawater by capillary zone electrophoresis with chloride-induced sample self-stacking. J Chromatogr A 2002; 966:205-12. [PMID: 12214695 DOI: 10.1016/s0021-9673(02)00744-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A capillary zone electrophoresis (CZE) method was established to determine low concentration nitrate which was online preconcentrated with chloride-induced leading-type sample self-stacking for seawater samples. The sample self-stacking was based on transient isotachophoresis in which chloride served as leading ion, and dihydrogenphosphate in the background electrolyte (0.1 M phosphate) as the terminating one. Due to the small mobility difference between nitrate and chloride, the isotachophoresis time was so long that nitrate could not separate from the rear sharp boundary between chloride and the background electrolyte (BGE) when it migrated to the detection window. A zwitterionic surfactant, 3-(N,N-dimethyldodecylammonio)propane sulfonate was added to the BGE to enlarge the mobility difference for its selective interaction with anions. Thus, a highly conductive sample could be injected in a large volume with about fourfold sensitivity enhancement compared to that of field amplification sample stacking in which nitrate was dissolved in pure water. The relative standard deviations (n=5) of migration time, peak area, peak height were 0.1, 3.0, 1.5%, respectively. The limit of detection (S/N=3) for nitrate was 35 microg/l in seawater samples with relatively low concentration BGE (0.1 M sodium phosphate, pH 6.2). The overall procedure consisting of online preconcentration and separation was as simple as routine CZE except for a slightly longer sample injection time (3-4 min).
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Affiliation(s)
- Chuanhong Tu
- Department of Chemistry, National University of Singapore, Singapore
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Yokoyama T, Macka M, Haddad PR. Determination of association constants of inorganic ions with C12- and C14-alkyldimethylammoniopropane sulfonate zwitterionic surfactants using capillary electrochromatography. Anal Chim Acta 2001. [DOI: 10.1016/s0003-2670(01)01177-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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