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Abstract
Microemulsion electrokinetic chromatography (MEEKC) is a special mode of capillary electrophoresis employing a microemulsion as carrier electrolyte. Analytes may partition between the aqueous phase of the microemulsion and its oil droplets which act as a pseudostationary phase. The technique is well suited for the separation of neutral species, in which case charged oil droplets (obtained by addition of an anionic or cationic surfactant) are present. A single set of separation parameters may be sufficient for separation of a wide range of analytes belonging to quite different chemical classes. Fine-tuning of resolution and analysis time may be achieved by addition of organic solvents, by changes in the nature of the surfactants (and cosurfactants) used to stabilize the microemulsion, or by various additives that may undergo some additional interactions with the analytes. Besides the separation of neutral analytes (which may be the most important application area of MEEKC), it can also be employed for cationic and/or anionic species. In this chapter, MEEKC conditions are summarized that have proven their reliability for routine analysis. Furthermore, the mechanisms encountered in MEEKC allow an efficient on-capillary preconcentration of analytes, so that the problem of poor concentration sensitivity of ultraviolet absorbance detection is circumvented.
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Affiliation(s)
- Wolfgang Buchberger
- Institut für Analytische Chemie, Universität Linz, TNF-Tower, T 209, Altenbergerstraße 69, Linz, 4040, Austria.
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Chang CW, Chen YC, Liu CY. Separation and on-line preconcentration of nonsteroidal anti-inflammatory drugs by microemulsion electrokinetic chromatography. Electrophoresis 2015; 36:2745-2753. [DOI: 10.1002/elps.201500160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 07/22/2015] [Accepted: 07/23/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Chia-Wen Chang
- Department of Chemistry; National Taiwan University; Taipei Taiwan
| | - Yu-Cheng Chen
- Department of Chemistry; National Taiwan University; Taipei Taiwan
| | - Chuen-Ying Liu
- Department of Chemistry; National Taiwan University; Taipei Taiwan
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Hermawan D, Yatim IM, Rahim KA, Sanagi MM, Ibrahim WAW, Aboul-Enein HY. Comparison of HPLC and MEEKC for Miconazole Nitrate Determination in Pharmaceutical Formulation. Chromatographia 2013. [DOI: 10.1007/s10337-013-2390-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Yang H, Ding Y, Cao J, Li P. Twenty-one years of microemulsion electrokinetic chromatography (1991-2012): A powerful analytical tool. Electrophoresis 2013; 34:1273-94. [DOI: 10.1002/elps.201200494] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 12/18/2012] [Accepted: 01/22/2013] [Indexed: 12/18/2022]
Affiliation(s)
- Hua Yang
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
| | - Yao Ding
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
| | - Jun Cao
- College of Material Chemistry and Chemical Engineering; Hangzhou Normal University; Hangzhou; P. R. China
| | - Ping Li
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
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Glatz Z. Application of short-end injection procedure in CE. Electrophoresis 2013; 34:631-42. [DOI: 10.1002/elps.201200506] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Revised: 10/12/2012] [Accepted: 10/20/2012] [Indexed: 11/05/2022]
Affiliation(s)
- Zdeněk Glatz
- Department of Biochemistry; Faculty of Science and CEITEC; Masaryk University; Brno; Czech Republic
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Yu L, Chu K, Ye H, Liu X, Yu L, Xu X, Chen G. Recent advances in microemulsion electrokinetic chromatography. Trends Analyt Chem 2012. [DOI: 10.1016/j.trac.2011.11.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Chen Z, Lin Z, Zhang L, Cai Y, Zhang L. Analysis of plant hormones by microemulsion electrokinetic capillary chromatography coupled with on-line large volume sample stacking. Analyst 2012; 137:1723-9. [DOI: 10.1039/c2an16313f] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Huang HY, Liu WL, Singco B, Hsieh SH, Shih YH. On-line concentration sample stacking coupled with water-in-oil microemulsion electrokinetic chromatography. J Chromatogr A 2011; 1218:7663-9. [DOI: 10.1016/j.chroma.2011.05.091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 04/28/2011] [Accepted: 05/26/2011] [Indexed: 02/06/2023]
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9
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Maijó I, Borrull F, Calull M, Aguilar C. An in-line SPE strategy to enhance sensitivity in CE for the determination of pharmaceutical compounds in river water samples. Electrophoresis 2011; 32:2114-22. [DOI: 10.1002/elps.201100054] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/29/2011] [Accepted: 05/03/2011] [Indexed: 11/05/2022]
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10
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Botello I, Borrull F, Calull M, Aguilar C. Simultaneous determination of weakly ionizable analytes in urine and plasma samples by transient pseudo-isotachophoresis in capillary zone electrophoresis. Anal Bioanal Chem 2011; 400:527-34. [DOI: 10.1007/s00216-011-4758-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/28/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
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11
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Analyses of non-steroidal anti-inflammatory drugs by on-line concentration capillary electrochromatography using poly(stearyl methacrylate–divinylbenzene) monolithic columns. J Chromatogr A 2011; 1218:350-8. [DOI: 10.1016/j.chroma.2010.11.040] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 11/16/2010] [Accepted: 11/18/2010] [Indexed: 11/23/2022]
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12
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Botello I, Borrull F, Aguilar C, Calull M. Electrokinetic supercharging focusing in capillary zone electrophoresis of weakly ionizable analytes in environmental and biological samples. Electrophoresis 2010; 31:2964-73. [DOI: 10.1002/elps.201000184] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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13
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Zhang W, Chen JF, Fan LY, Cao CX, Ren JC, Li S, Shao J. A novel isotachophoresis of cobalt and copper complexes by metal ion substitution reaction in a continuous moving chelation boundary. Analyst 2010; 135:140-8. [DOI: 10.1039/b912799b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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KUO YL, LIU WL, HSIEH SH, HUANG HY. Analyses of Non-steroidal Anti-inflammatory Drugs in Environmental Water Samples with Microemulsion Electrokinetic Chromatography. ANAL SCI 2010; 26:703-7. [DOI: 10.2116/analsci.26.703] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yu-Ling KUO
- Department of Chemistry and Center for Nano Technology at CYCU, Chung Yuan Christian University
| | - Wan-Ling LIU
- Department of Chemistry and Center for Nano Technology at CYCU, Chung Yuan Christian University
| | - Shih-Huan HSIEH
- Department of Chemistry and Center for Nano Technology at CYCU, Chung Yuan Christian University
| | - Hsi-Ya HUANG
- Department of Chemistry and Center for Nano Technology at CYCU, Chung Yuan Christian University
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Yu LS, Xu XQ, Huang L, Lin JM, Chen GN. Separation and detection of isoquinoline alkaloids using MEEKC coupled with field-amplified sample injection induced by ACN. Electrophoresis 2009; 30:661-7. [DOI: 10.1002/elps.200800555] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Drover VJ, Bottaro CS. Determination of pharmaceuticals in drinking water by CD-modified MEKC: Separation optimization using experimental design. J Sep Sci 2008; 31:3740-8. [DOI: 10.1002/jssc.200800337] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Starek M, Krzek J, Stoch M. Densitometric analysis of 2-arylpropionate derivatives in pharmaceutical preparations. JPC-J PLANAR CHROMAT 2008. [DOI: 10.1556/jpc.21.2008.4.5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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18
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Almeda S, Arce L, Valcárcel M. Combination of solid-phase extraction and large-volume stacking with polarity switching in micellar electrokinetic capillary chromatography for the determination of traces of nonsteroidal anti-inflammatory drugs in saliva. Electrophoresis 2008; 29:3074-80. [DOI: 10.1002/elps.200800023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Yu L, Xu X, Huang L, Lin J, Chen G. Microemulsion electrokinetic chromatography coupling with field amplified sample injection and electroosmotic flow suppressant for analysis of some quinolizidine alkaloids. J Chromatogr A 2008; 1198-1199:220-5. [DOI: 10.1016/j.chroma.2008.05.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/10/2008] [Accepted: 05/14/2008] [Indexed: 11/28/2022]
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Cao J, Chen J, Yi L, Li P, Qi LW. Comparison of oil-in-water and water-in-oil microemulsion electrokinetic chromatography as methods for the analysis of eight phenolic acids and five diterpenoids. Electrophoresis 2008; 29:2310-20. [DOI: 10.1002/elps.200700749] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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21
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Zhu J, Qi S, Zhang H, Chen X, Hu Z. Sample stacking and sweeping in microemulsion electrokinetic chromatography under pH-suppressed electroosmotic flow. J Chromatogr A 2008; 1192:319-22. [DOI: 10.1016/j.chroma.2008.04.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Revised: 04/01/2008] [Accepted: 04/02/2008] [Indexed: 11/25/2022]
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Dawod M, Breadmore MC, Guijt RM, Haddad PR. Electrokinetic supercharging for on-line preconcentration of seven non-steroidal anti-inflammatory drugs in water samples. J Chromatogr A 2008; 1189:278-84. [DOI: 10.1016/j.chroma.2007.12.056] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Revised: 12/07/2007] [Accepted: 12/12/2007] [Indexed: 10/22/2022]
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23
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Simpson SL, Quirino JP, Terabe S. On-line sample preconcentration in capillary electrophoresis. J Chromatogr A 2008; 1184:504-41. [DOI: 10.1016/j.chroma.2007.11.001] [Citation(s) in RCA: 269] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 10/30/2007] [Accepted: 11/01/2007] [Indexed: 02/06/2023]
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Macià A, Borrull F, Calull M, Benavente F, Hernández E, Sanz-Nebot V, Barbosa J, Aguilar C. Sensitivity enhancement for the analysis of naproxen in tap water by solid-phase extraction coupled in-line to capillary electrophoresis. J Sep Sci 2008; 31:872-80. [DOI: 10.1002/jssc.200700593] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Wu CH, Chen TH, Huang KP, Wang GR, Liu CY. Separation of corticosteroids by microemulsion EKC with diethylL-tartrate as the oil phase. Electrophoresis 2007; 28:3691-6. [PMID: 17893939 DOI: 10.1002/elps.200700358] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A novel microemulsion based on a mixture of diethyl L-tartrate (DET) and SDS was developed for the microemulsion EKC (MEEKC) determination of structurally related steroids. The system consisted of 0.5% w/w DET, 1.7% w/w SDS, 1.2% w/w 1-butanol, 89.6% w/w phosphate buffer (40 mM, pH 7.0), and 7% w/w ACN. With an applied voltage of +10 kV, a baseline separation of aldosterone (A), cortisone acetate (CA), dexamethasone (D), hydrocortisone (H), hydrocortisone acetate (HA), prednisolone (P), prednisolone acetate (PA), prednisone (Ps), triamcinolone (T), and triamcinolone acetonide (TA) could be achieved. Under the optimized conditions, the reproducibility of the retention time (n = 4) for most of the compounds was less than +/-0.8% with the exception of A, Ps, and T. The average number of theoretical plates was 18 800 plates/m. The results were compared with those achieved by the modified micellar EKC (MEKC). MEEKC showed obvious advantages over MEKC for the separation of highly hydrophobic substances. To further evaluate the system, we tested the MEEKC method by analyzing corticosteroids in a spiked urine sample.
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Affiliation(s)
- Chi-Hung Wu
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
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Huang HY, Hsieh SH. Analyses of tobacco alkaloids by cation-selective exhaustive injection sweeping microemulsion electrokinetic chromatography. J Chromatogr A 2007; 1164:313-9. [PMID: 17644105 DOI: 10.1016/j.chroma.2007.06.065] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 06/27/2007] [Accepted: 06/28/2007] [Indexed: 11/25/2022]
Abstract
In this study, an on-line concentration method which coupled cation-selective exhaustive injection (CSEI) sweeping technology with microemulsion electrokinetic chromatography (MEEKC) was used to detect and analyze several tobacco alkaloids (nornicotine, anabasine, anatabine, nicotine, myosmine and cotinine) that are commonly found in various tobacco products. First, the effects of microemulsion compositions (oil, cosurfactant and solution pH) were examined in order to optimize the alkaloid separations in conventional MEEKC. The pH value and the injection length of basic plug were found to be the predominant influences on the alkaloid stacking. This optimal CSEI sweeping MEEKC method provided approximately 180- to 540-fold increase in detection sensitivity in terms of peak height without any loss in separation efficiency when compared to normal MEEKC separation. Furthermore, this proposed CSEI sweeping MEEKC method was applied successfully for the detection of the minor alkaloids nornicotine, anabasine and anatabine in tobacco products.
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Affiliation(s)
- Hsi-Ya Huang
- R&D Center for Membrane Technology, Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li, Taiwan.
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Nemec T, Glatz Z. Integration of short-end injection mode into electrophoretically mediated microanalysis. J Chromatogr A 2007; 1155:206-13. [PMID: 17292907 DOI: 10.1016/j.chroma.2007.01.074] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 01/08/2007] [Accepted: 01/18/2007] [Indexed: 10/23/2022]
Abstract
The possibility of integration of the short-end injection mode in the EMMA methodology is demonstrated in this work on the kinetic studies of haloalkane dehalogenase and rhodanese enzymatic reactions. The essential validations of the EMMA methods combined with the short-end and long-end injection modes were performed first to confirm their accuracy. The qualitative and quantitative parameters of both approaches such as repeatabilities of migration times and peak areas, limits of detection and correlation coefficients were in acceptable ranges. In addition, estimated Michaelis constants for the corresponding substrate(s) were comparable being in accordance with previous literature data. Moreover, the ping-pong reaction mechanism of rhodanese reaction was confirmed by means of both injection modes. This combination thus preserves the benefits of these instrumental approaches. Whereas the short-end injection procedure brought 5-6.5 times reduction of the analysis time and 2.5-4 times increase of the sensitivity, the EMMA methodology allowed full automatization of the assays while the whole kinetic studies needed only 20 microl of corresponding enzyme preparation.
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Affiliation(s)
- Tomás Nemec
- Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
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Huang HY, Huang IY, Liang HH, Lee S. Sample stacking for the analysis of catechins by microemulsion EKC. Electrophoresis 2007; 28:1735-43. [PMID: 17464960 DOI: 10.1002/elps.200600413] [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] [Indexed: 11/10/2022]
Abstract
In this study, an on-line concentration method, ASEI (anion-selective exhaustive injection)-sweeping technology which was coupled with microemulsion EKC (MEEKC), was used to analyze and detect six catechins ((-)-epicatechin, (+)-catechin, (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, and (-)-gallocatechin). In addition to the effects of the buffer pH and electrolyte concentration on stacking, the compositions of microemulsion (types of oil phase, and types and levels of cosurfactant) also dominated the stacking effect of catechins. In MEEKC, the effect of the type of oil in microemulsion on separation mechanism is often unclear. This study had demonstrated that the oil type in microemulsion indeed altered the affinity of oil droplets with analytes. Finally, this proposed ASEI-sweeping MEEKC method was able to detect trace level of catechins in food products that was not previously possible by a normal MEEKC method.
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Affiliation(s)
- Hsi-Ya Huang
- R&D Center for Membrane Technology, Department of Chemistry, Center for Nanotechnology at CYCU, Chung Yuan Christian University, Chung-Li, Taiwan, R.O.C.
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Malá Z, Krivánková L, Gebauer P, Bocek P. Contemporary sample stacking in CE: A sophisticated tool based on simple principles. Electrophoresis 2007; 28:243-53. [PMID: 17136738 DOI: 10.1002/elps.200600397] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sample stacking is a general term for methods in CE which are used for on-line concentration of diluted analytes. During the stacking process, analytes present at low concentrations in a long injected sample zone are concentrated into a short zone (stack). The stacked analytes are then separated and individual zones are detected. Thus stacking provides better separation efficiency and detection sensitivity. Many papers have been published on stacking till now, various procedures have been described, and, many names have been proposed for stacking procedures utilizing the same principles. This contribution brings an easy and unified view on stacking, describes the basic principles utilized, makes a list of recognized operational principles and brings an overview of principal current procedures. Further, it surveys selected recent practical applications ordered according to their operational principles and includes the terms, nicknames, and acronyms used for these actual stacking procedures. This contribution may help both newcomers and experts in the field of CE to orient themselves in the already quite complex topic of sample stacking.
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Affiliation(s)
- Zdena Malá
- Institute of Analytical Chemistry, Academy of Sciences of the Czech Republic, Brno, Czech Republic
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McEvoy E, Marsh A, Altria K, Donegan S, Power J. Recent advances in the development and application of microemulsion EKC. Electrophoresis 2007; 28:193-207. [PMID: 17136741 DOI: 10.1002/elps.200600451] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Microemulsion EKC (MEEKC) is an electrodriven separation technique. Separations are typically achieved using oil-in-water microemulsions, which are composed of nanometre-sized oil droplets suspended in an aqueous buffer. The droplets are stabilised by a surfactant and a cosurfactant. The novel use of water-in-oil microemulsions has also been investigated. This review summarises the advances in the development of MEEKC separations and also the different areas of application including determination of log P values, pharmaceutical applications, chiral analysis, natural products and bioanalytical separations and the use of new methods such as multiplexed MEEKC and high speed MEEKC. Recent applications (2004-2006) are tabulated for each area with microemulsion composition details.
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Affiliation(s)
- Eamon McEvoy
- Department of Chemical and Life Sciences, Waterford Institute of Technology, Cork Road, Waterford, Ireland.
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Ding Y, Garcia C. Determination of Nonsteroidal Anti-inflammatory Drugs in Serum by Microchip Capillary Electrophoresis with Electrochemical Detection. ELECTROANAL 2006. [DOI: 10.1002/elan.200603648] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Huang HY, Lien WC, Huang IY. Anion-selective exhaustive injection-sweeping microemulsion electrokinetic chromatography. Electrophoresis 2006; 27:3202-9. [PMID: 16850505 DOI: 10.1002/elps.200500876] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this study, anion-selective exhaustive injection-sweeping (ASEI-sweeping) technique, which is a selective on-line sample concentration technique, was first proposed in microemulsion electrokinetic chromatography (MEEKC) for analyses of eight acidic phenolic compounds. In contrast to a capillary that is typically filled with nonmicellar background solution in conventional ASEI-sweeping MEKC method, in the proposed ASEI-sweeping MEEKC method, a capillary is filled with a low pH microemulsion solution (pH 2.0), and then with a short acid plug (pH 2.0, 1.9 cm) before field-amplified sample injection. This proposed design has two functions. First, the microemulsion solution that is present at the front of capillary column is able to avoid phase separation of microemulsion solution during MEEKC separation. Second, the presence of the short acid plug would effectively limit the partition behavior of acid analytes with the oil droplets in the microemulsion during field-amplified sample injection; otherwise, the stacking effect of acid analytes would be markedly reduced. This optimal ASEI-sweeping MEEKC method afforded about 96,000-fold to 238,000-fold increases in detection sensitivity in terms of peak areas without any separation efficiency loss when compared to normal MEEKC separation. Furthermore, trace levels (about 3 ng/g) of gallic acid and catechin in foods were also detected successfully by the proposed ASEI-sweeping MEEKC technique.
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Affiliation(s)
- Hsi-Ya Huang
- Department of Chemistry, Center for Nanotechnology at CYCU, Chung Yuan Christian University, Chung-Li, Taiwan, China.
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Macià A, Borrull F, Calull M, Aguilar C. Different sample stacking strategies to analyse some nonsteroidal anti-inflammatory drugs by micellar electrokinetic capillary chromatography in mineral waters. J Chromatogr A 2006; 1117:234-45. [PMID: 16600264 DOI: 10.1016/j.chroma.2006.03.076] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 03/20/2006] [Accepted: 03/22/2006] [Indexed: 11/22/2022]
Abstract
Three on-column preconcentration techniques were compared to analyse a group of nonsteroidal anti-inflammatory drugs (NSAIDs) using micellar electrokinetic capillary chromatography (MEKC) under pH-suppressed electroosmotic flow (EOF) in water samples. The analysed drugs were ibuprofen, fenoprofen, naproxen, ketoprofen, and diclofenac sodium. The micellar background electrolyte (BGE) solution was formed by 75 mM sodium dodecyl sulfate (SDS), 40% (v/v) acetonitrile, and 25 mM sodium phosphate at pH 2.5. When this BGE solution was used the applied voltage was reversed, -10 kV, and the drugs were separated within 20 min. The on-column preconcentration modes, characterised all of them for the sample matrix removal out of the capillary by itself under a reverse potential at the same time as the EOF was reduced, were stacking with reverse migrating micelles (SRMM), stacking with reverse migrating micelles-anion selective exhaustive injection (SRMM-ASEI), and field-enhanced sample injection with reverse migrating micelles (FESI-RMM). The sensitivity was improved up to 154-, 263-, and 63-fold, respectively when it was calculated through the peaks height. The optimised methods were validated with spiked mineral water by combining off-line solid-phase extraction (SPE) and the proposed on-line sample stacking strategies. The detection limits (LODs) of NSAIDs in mineral water were at ng/L levels.
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Affiliation(s)
- Alba Macià
- Department of Analytical Chemistry and Organic Chemistry, University Rovira i Virgili, C/Marcel.li Domingo s/n, 43007 Tarragona, Spain
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Abstract
Compared to MEKC, the presence of a water-immiscible oil phase in the microemulsion droplets of microemulsion EKC (MEEKC) gives rise to some special properties, such as enhanced solubilization capacity and enlarged migration window, which could allow for the improved separation of various hydrophobic and hydrophilic compounds, with reduced sample pretreatment steps, unique selectivities and/or higher efficiencies. Typically, stable and optically clear oil-in-water microemulsions containing a surfactant (SDS), oil (octane or heptane), and cosurfactant (1-butanol) in phosphate buffer are employed as separation media in conventional MEEKC. However, in recent years, the applicability of reverse MEEKC (water-in-oil microemulsions) has also been demonstrated, such as for the enhanced separation of highly hydrophobic substances. Also, during the past few years, the development and application of MEEKC for the separation of chiral molecules has been expanded, based on the use of enantioselective microemulsions that contained a chiral surfactant or chiral alcohol. On the other hand, the application of MEEKC for the characterization of the lipophilicity of chemical substances remains an active and important area of research, such as the use of multiplex MEEKC for the high-throughput determination of partition coefficients (log P values) of pharmaceutical compounds. In this review, recent applications of MEEKC (covering the period from 2003 to 2005) are reported. Emphases are placed on the discussion of MEEKC in the separation of chiral molecules and highly hydrophobic substances, as well as in the determination of partition coefficients, followed by a survey of recent applications of MEEKC in the analysis of pharmaceuticals, cosmetics and health-care products, biological and environmental compounds, plant materials, and foods.
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Affiliation(s)
- Carmen W Huie
- Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.
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36
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Macià A, Borrull F, Calull M, Aguilar C. Analysis of Nonsteroidal Anti-inflammatory Drugs in Water Samples Using Microemulsion Electrokinetic Capillary Chromatography Under pH-Suppressed Electroosmotic Flow with an On-Column Preconcentration Technique. Chromatographia 2006. [DOI: 10.1365/s10337-006-0723-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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37
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Puig P, Borrull F, Aguilar C, Calull M. Sample stacking for the analysis of penicillins by microemulsion electrokinetic capillary chromatography. J Chromatogr B Analyt Technol Biomed Life Sci 2006; 831:196-204. [PMID: 16386475 DOI: 10.1016/j.jchromb.2005.12.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 11/30/2005] [Accepted: 12/05/2005] [Indexed: 11/12/2022]
Abstract
We present a method for determining eight penicillin antibiotics using microemulsion electrokinetic chromatography (MEEKC). We studied how the composition of the microemulsion affected separation by modifying such parameters as the surfactant or the addition of organic solvents. The best microemulsion system consisted of 0.5% ethyl acetate, 1.2% 1-butanol, 2% Brij 35, 10% 2-butanol and 86.3% 10 mM borate buffer at pH 10. We studied the suitability of this microemulsion composition for analyzing a commercial drug. To improve the sensitivity of the method, we used the stacking technique reversed electrode polarity stacking mode (REPSM), which increased the detection limits by about 40-fold.
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Affiliation(s)
- Patricia Puig
- Department of Analytical Chemistry and Organic Chemistry, Rovira i Virgili University, Marcel lí Domingo s/n, E-43007 Tarragona, Spain
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38
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Puig P, Borrull F, Calull M, Aguilar C. Strategies for Analyzing Cephalosporins by Microemulsion Electrokinetic Chromatography. Chromatographia 2005. [DOI: 10.1365/s10337-005-0685-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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