核黃素（又稱維他命B2）是一種水溶性的維他命，乃是一種人體必須的微量元素，是黃素單核甘酸（flavin mononucleotide）與黃素腺嘌呤二核甘酸（flavin adenine dinucleotide）此兩輔脢的前趨物，這些輔脢對人體是必須的，尤其是在人體內碳水化合物的氧化還原反應，扮演著重要的角色。維他命B2在高溫、儲存以及食物烹飪的過程中都非常的穩定，但若是暴露於光源下，則會快速的分解。
本研究發現使用毛細管電泳/藍光光二極體（Blue LED）誘導螢光偵測法結合堆積（stacking）與速度變化誘導聚焦（velocity-difference induced focusing, V-DIF）兩線上濃縮技術，可以提供一簡單、快速且極具經濟效益的分析技術，對於在尿液、啤酒以及香菇等真實樣品中的維他命B2，做直接且重複的測定。以藍光LED作為誘導螢光光源，對維他命B2的偵測靈敏度為480 ng/ml，當結合stacking與V-DIF兩線上濃縮技術時，則可改善至20 ng/ml與1 ng/ml（2.6 ×10-9 M）。分析尿液樣品時，對服用過一顆複合維他命藥碇的試驗者，其尿液中維他命B2在九個小時內的代謝變化情形；對於分析食物類的樣品，可以對12種不同品牌的市售啤酒，測定其維他命B2含量的分佈範圍在130~280 ng/ml，以及對6朵不同大小的市售台產香菇，測定其維他命B2含量的分佈範圍在3.4~11.2 μg/g（ppm）。

Riboflavin (vitamin B2) is a water-soluble vitamin and micronutrient, which is metabolized into two coenzymes, flavin adenine dinucleotide and flavin mononucleotide. These coenzymes are needed for the activity of flavoenzymes implicated in redox reactions. Riboflavin is very stable during thermal processing, storage, and food preparation but is susceptible to degradation on exposure to light. A simple, inexpensive and reliable method for the simultaneous, routine analysis of riboflavin in actual samples: urine, beer, and mushroom by capillary electrophoresis-blue light emitting diode (LED)-induced fluorescence detection combined with stacking and velocity-difference induced focusing by using a dynamic pH junction techniques.
Using a blue LED as the light source, the detection limit of riboflavin was determined to be 480 ng/ml and was improved to 20 ng/ml and 1 ng/ml (2.6 × 10-9 M) when stacking and V-DIF techniques was applied. In the analysis of urine samples, various concentrations of riboflavin were distributed over a period of 9 hours after the ingestion of a vitamin B2 tablet. In the analysis of food samples, the concentrations of riboflavin in 12 kinds of different types of commercial beer were found to be in the range of 130-280 ng/ml, and the concentrations of riboflavin in 6 kinds of different types of mushroom were found to be in the range of 3.4-11.2 μg/g (ppm).

[1] P. F. Heelis, in: F. Müller (Ed.), Flavins and Flavoproteins, CRC Press, Boca Raton, FL, (1991) 171.
[2] T. R. I. Cataldi, D. Nardiello, G. E. De Benedetto, S. A. Bufo, Optimizing separation conditions for riboflavin, flavin mononucleotide and flavin adenine dinucleotide in capillary zone electrophoresis with laser-induced fluorescence detection, J. Chromatogr. A 968 (2002) 229.
[3] F. Valls, M. T. Sancho, M. A. fernández-Muiño, M. A. Checa, Determination of total riboflavin in cooked sausages, J. Agric. Food Chem. 47 (1999) 1067.
[4] C. D. Capo-chichi, J.-L. Guéant, F. Feillet, F. Namour, M. Vidailhet, Analysis of riboflavin and riboflavin cofactor levels in plasma by high-performance liquid chromatography, J. Chromatogr. B 739 (2000) 219.
[5] S. Hustad, P. M. Ueland, J. Schneede, Quantification of riboflavin, flavin mononucleotide, and flavin adenine dinucleotide in human plasma by capillary electrophoresis and laser-induced fluorescence detection, Clin. Chem. 45:6 (1999) 862.
[6] T. R. I. Cataldi, D. Nardiello, L. Scrano, A. Scopa, Assay of riboflavin in sample wines by capillary zone electrophoresis and laser-induced fluorescence detection, J. Agric. Food Chem. 50 (2002) 6643.
[7] J. H. Wassink, S. G. Mayhew, Fluorescence titration with apoflavodoxin: a sensitive assay for riboflavin 5’-phosphate and flavin adenine dinucleotide in mixtures, Anal. Biochem. 68 (1975) 609.
[8] J. A. Tillotson, M. M. Bashor, Fluorometric apoprotein titration of urinary riboflavin, Anal. Biochem. 107 (1980) 214.
[9] M. G. Duyvis, R. Hilhorst, C. Laane, D. J. Evans, D. J. M. Schmedding, Role of riboflavin in beer flavor instability: determination of levels of riboflavin and its origin in beer by fluorometric apoprotein titration, J. Agric. Food Chem. 50 (2002) 1548.
[10] W. Tong, E. S. Yeung, Simple double-beam absorption detection systems for capillary electrophoresis based on diode lasers and light-emitting diodes, J. Chromatogr. A 718 (1995) 177.
[11] Q. Lu, G. E. Collins, Microchip separations of transition metal ions via LED absorbance detevtion of their PAR complexes, Analyst 126 (2001) 429.
[12] Q. Lu, G. E. Collins, Microfabricated capillary electrophoresis sensor for uranium (VI), Anal. Chim. Acta 436 (2001) 181.
[13] S. L. Wang, X. J. Huang, Z. L. Fang, A miniaturized liquid core waveguide-capillary electrophoresis system with flow injection sample pntroductuin and fluorometric detection using light-emitting diodes, Anal. Chem. 73 (2001) 4545.
[14] N. Vachirapatama, P. Doble, Z. Yu, M. Macka, P. R. Haddad, Separation of niobium (V) and tantalum (V) as ternary complexes with citrate and metallochromic ligands by capillary electrophoresis, Anal. Chim. Acta 434 (2001) 301.
[15] P. A. G. Butler, B. Mills, P. C. Hauser, Capillary electrophoresis detector using a light emitting diode and optical fibres, Analyst 122 (1997) 949.
[16] K. Uchiyama, W. Xu, J. Qiu, T. Hobo, Polyester microchannel chip for eoectrophoresis-incorporation of a blue LED as light source, Fresen. J. Anal. Chem. 371 (2001) 209.
[17] S.-C. Wang, M. D. Morris, Plastic microchip electrophoresis with analyte velocity modulation. Application to fluorescence background rejection, Anal. Chem. 72 (2000) 1448.
[18] J. C. Bates, Bioavailability of riboflavin, Eur. J. Clin. Nutr. 51 (1997) 38.
[19] V. Massey, Activation of molecular oxygen by flavins and flavoproteins, J. Biol. Chem. 269 (1994) 22459.
[20] P. C. Hu, B. H. Chen, Effects of riboflavin and fatty acid methyl esters on cholesterol oxidation during illumination, J. Agric. Food Chem. 50 (2002) 3572.
[21] I. Siddiqui, K. S. Pitre, Voltammetric determination of vitamins in a pharmaceutical formulation, J. Pharm. Biomed. Anal. 26 (2001) 1009.
[22] J. P. Hart, Polarographic and Voltammetric Techniques and Their Application to the Determination of Vitamins and Coenzymes, Trends Anal. Chem. 5 (1986) 20.
[23] C. Y. W. Ang, F. A. Moseley, Determination of thiamin and riboflavin in meat and meat products by high-pressure liquid chromatography, J. Agric. Food Chem. 28 (1980) 483.
[24] Analytical Methods Committee, Analyst 125 (2000) 353.
[25] C. Andréa, F. Mattivi, D. Tonon, Determination of riboflavin flavin minonucleotide and flavinadenine dinucleotide in wine and other beverages by hight-performance liquid chromatography with fluorescence detection, J. Chromatogr. A 823 (1998) 355
[26] F. Arella, S. Lahély, J. B. Bourguignon, C. Hasselmann, Liquid chromatographic determination of vitamins B1 and B2 in foods. A collaborative study, Food Chem. 56 (1996) 81.
[27] A. Gliszczyńska-Świgło, A. Koziołowa, Chromatographic determination of riboflavin and its derivatives in food, J. Chromatogr. A 881 (2000) 285.
[28] A. Gliszczyńska-Świgło, A. Koziołowa, Chromatographic identification of a new flavin derivate in plain yogurt, J. Agric. Food Chem. 47 (1999) 3197.
[29] A. Gliszczyńska-Świgło, A. Koziołowa, Chromatographic determination of flavin derivates in baker’s yeast, J. agric. Food Chem. 822 (1998) 59.
[30] F. Mattivi, A. Monetti, U. Vrhovšeket, D. Tonon, C. Andrés- Lacueva, High-performance liquid chromatographic determination of the riboflavin concentration in white wines for predicting their resistance to light, J. Chromatogr. A 888 (2000) 121.
[31] L. Fotsing, M. Fillet, I. Bechet, Ph. Hubert, J. Crommen, Determination of six water-soluble vitamins in a pharmaceutical formulation by capillary electrophoresis, J. Pharm. Biomed. Anal. 15 (1999) 1113.
[32] P. Moreno, V. Salvadó, Determination of eight water- and fat-soluble vitamins in multi-vitamin pharmaceutical formulations by high-performance liquid chromatography, J. Chromatogr. A 870 (2000) 207.
[33] M.-J. Esteve, R. Farré, A. Frígola, J.-M. García-Cantabella, Simultaneous determination of thiamin and riboflavin in mushrooms by liquid chromatography, J. Agric. Food Chem. 49 (2001) 1450.
[34] L. F. Russell, L. Brooks, K. B. McRae, Development of a robotic-HPLC determination of riboflavin vitaminers in food, Food Chem. 63 (1997) 125.
[35] S. M. Fernaddo, P. A. Murphy, HPLC determination of thiamin and riboflavin in soybeans and tofu, J. Agric. Food Chem. 38 (1990) 163.
[36] R. L. Wehling, D. L. Wetzel, Simultaneous determination of pyridoxine, riboflavin, and thiamin in fortified cereal products by high-performance liquid chromatography, J. Agric. Food Chem. 32 (1984) 1326.
[37] T. Pérez-Ruiz, C. Martínez-Lozano, A. Sanz, E. Bravo, Determination of riboflavin, flavin mononucleotide and flvin adenine dinucleotide in biological tissues by capillary zone electrophoresis and laser-induced fluorescence detection, Electrophoresis 22 (2001) 1170.
[38] P. Britz-McKibbin, K. Otsuka, S. Terabe, On-line focusing of flavin derivatives using dynamic pH junction-sweeping capillary electrophoresis with laser-induced fluorescence detection, Anal. Chem. 74 (2002) 3736.
[39] M. S. Bellini, G. Manetto, Z. Deyl, F. Tagliaro, I. Mikšík, Capillary electrophoresis separation of vitamins in sodium dodecyl sulfate containing buffers with lower aliphatic alcohols and n-hexane as organic modifiers, J. Chromatogr. B 741 (2000) 67.
[40] S. Buskov, P. Møller, H. Sørensen, J. C. Sørensen, S. Sørensen, Determination of vitamins in food based on supercritical fluid extraction prior to micellar electrokinetic capillary chromatographic analyses of induvidual vitamins, J. Chromatogr. A 802 (1998) 233.
[41] M. M. Delgado-Zamarreño, I. González-Maza, A. Sánchez-Pérez, R. Carabias-Martinez, Separation and simultaneous determination of water-soluble and fat-soluble vitamins by electrokinetic capillary chromatography, J. Chromatogr. A 953 (2002) 257.
[42] D. S. Burgi, Large volume stacking of anions in capillary electrophoresis using an electroosmitic flow modifier as a pump, Anal. Chem. 65 (1993) 3726.
[43] J. P. Quirino, S. Terabe, Exceeding 5000-fold concentration of dilute analytes in micellar electrokinetic chromatography, Science 282 (1998) 465.
[44] P. Britz-McKibbin , A. R. Kranack, A. Paprica, D. D. Y. Chen, Quantitative assay for epinephrine in dental anesthetic solutions by capillary electrophoresis, Analyst 123 (1998) 1461.
[45] F. Kohlrausch, Wiedemanns, Ueber Concentrations- Verschiebungen durch Electrolyse im Inneren von Lösungen und Lösungsgemischen, Ann. Phys. Chem. 62 (1897) 209.
[46] A. Tiselius, A new apparatus for electrophoretic analysis of colloidal mixtures, Trans. Faraday Soc. 33 (1937) 524.
[47] S. Hjerten, Free zone electrophoresis, Chromatogr. Rev 9 (1967) 122.
[48] R. Virtanen, Acta Polym. Sin. 123 (1979) 1.
[49] J. W. Joegenson, K. D. Lukacs, J. Chromatogr. 218 (1981) 209.
[50] J. W. Joegenson, K. D. Lukacs, Zone electrophoresis in open-tubular glass capillaries, Anal. Chem. 53 (1981) 1298.
[51] D. J. Rose, J. W. Joegenson, Characterization and automation of sample introduction methods for capillary zone electrophoresis, Anal. Chem. 60 (1988) 1840.
[52] K. Otsuka, K. Ichikawa, A. Tsuchiya, T. Ando, Electrokinetic separations with micellar solutions and open-tubular capillaries, Anal. Chem. 56 (1984) 111.
[53] S. Terabe, K. Otsuka, T. Ando, Electrokinetic chromatography with micellar solution and open-tubular capillary, Anal. Chem. 57 (1985) 834.
[54] K. H. Row, W. H. Griest, M. P. Maskarienc, J. Chromatogr. 409 (1987) 193.
[55] S. Hjerten, M. D. Zhu, Adaptation of the equipment for high-performance electrophoresis to isoelectric focusing, J. Chromatogr. 346 (1985) 265.
[56] S. Hjerten, J. L. Liao, K. Yao, Theoretical and experimental study of high performance electrophoreticmobilization of isoelectric focused protein zones, J. Chromatogr. 387 (1987) 127.
[57] A. Cohen, B. L. Karger, High-performance sodiumdodecyl sulfate polyacrylamide gel capillary electrophoresis of peptides and proteins, J. Chromatogr. 397 (1987) 409.
[58] X. Huang, R. N. Zare, Improved end-column conductivity detector for capillary zone electrophoresis, Anal. Chem. 63 (1991) 2193.
[59] R. D. Holland, M. J. Sepaniak, Qualitative analysis for mycotoxins using micellar electrokinetic capillary chromatography, Anal. Chem. 65 (1993) 1140.
[60] X. Huang, M. J. Gordon, R. N. Zare, Bias in quantitative capillary zone electrophoresis caused by electrokinetic sample injection, Anal. Chem. 60 (1993) 375.
[61] R. T. Kennedy, J. W. Gorgenson, Preparation and evaluation of packed capillary liquid chromatography columns with inner diameters from 20 to 50 micrometers, Anal. Chem. 61 (1989) 1128.
[62] M. M. Dittmann, G. P. Rozing, Capillary electrochromatography - a high-efficiency micro-separation technique, J. Chromatogr. A 744 (1996) 63.
[63] C. Y. Yan, R. Dadoo, R. N. Zare, D. J. Rakestraw, D. S. Anex, Thermal analysis, Anal. Chem. 68 (1996) 63.
[64] D. N. Heiger, Hewlett-Packard Company Publication Number 12-5091-6199E.
[65] H. Z. Helmholtz, Anal. Phys. Chem. 7 (1897) 337.
[66] B. Krattiger, G. J. M. Bruin, A. E. Bruin, Hologram-based refractive index detector for capillary electrophoresis: separation of metal ions, Anal. Chem. 66 (1994) 1.
[67] M. Stefansson, M. Novotny, Separation of complex oligosaccharide mixtures by capillary electrophoresis in the open-tubular format, Anal. Chem. 66 (1994) 1134.
[68] Y. Kim, M. D. Morris, Separation of nucleic acids by capillary electrophoresis in cellulose solutions with mono- and bisintercalating dyes, Anal. Chem. 66 (1994) 1168.
[69] Z. Zhzo, A. Malik, M. L. Lee, Adsorption on polymer-coated fused-silica capillary electrophoresis columns using selected protein and peptide standards, Anal. Chem. 65 (1994) 2747.
[70] A. J. G. Mank, E. S. Yeung, Diode laser-induced fluorescence detection in capillary electrophoresis after pre-column derivztization of amino acids and small peptides, J. Chromatogr. A 708 (1995) 309.
[71] S. V. Rahavendran, H. T. Karnes, Visible diode laser-induced fluorescence detection of phenylacetic acid in plasma derivatized with nile blue and using pre-column phase transfer catalysis, Anal. Chem. 69 (1997) 3022.
[72] D. L. Gallaher Jr., M. E. Johnson, Development of near-infrared fluorophoric labels for the determination of fatty acids separated by capillary electrophoresis with diode laser induced fluorescence detection, Analyst 124 (1999) 1541.
[73] A. J. G. Mank, H. Lingeman, C. Gooijer, Diode laser-based detection in liquid chromatography and capillary electrophoresis, Trends Anal. Chem. 15(1) (1996) 1.
[74] B. L. Legndre Jr., D. L. Moberg, D. C. Williams, S. A. Soper, Ultrasensitive near-infrared laser-induced fluorescence detection in capillary eoectrophoresis using a diode laser and avalanche photodiode, J. Chromatogr. A 779 (1997) 185.
[75] N. Kuroda, R. Nomura, O. Al-Dirbashi, S. Aliyama, K. Nakashima, Determination of methamphetamine and related compounds by capillary electrophoresis with UV and laser-induced fluorescence detection, J. Chromatogr. A 798 (1998) 325.
[76] T. Kaneta, H. Shiba, T. Imasaka, Determination of cyanine-labeled amino acid enantiomers by cyclodextrin-modified capillary gel electrophoresis combined with diode laser fluorescence detection, J. Chromatogr. A 805 (1998) 295.
[77] J. E. Melanson, C. A. Boulet, C. A. Lucy, Indirect laser-induced fluorescence detection for capillary electrophoresis using a violet diode laser, Anal. Chem. 73 (2001) 1809.
[78] J. E. Melanson, C. A. Lucy, Violet (405 nm) diode laser for laser induced fluorescence detection in capillary electrophoresis, Analyst 125 (2000) 1049.
[79] S. E. Moring, R. T. Reel, E. J. S. Remco, Optical improvements of a Z-shaped cell for high-sensitivity UV absorbance detection in capillary electrophoresis, Anal. Chem. 65 (1993) 3454.
[80] J. P. Quirino, S. Terabe, K. Otsuka, J. B. Vincent, G. Vigh, Sample concentration by sample stacking and sweeping using a microemulsion and a single-isomer sulfated β-cyclodextrin as pseudostationary phases in electrokinetic chromatography, J. Chromatogr. A 838 (1999) 3.
[81] J. P. Quirino, S. Terabe, Sample stacking of cationic and anionic analytes in capillary electrophoresis, J. Chromatogr. A 902 (2000) 119.
[82] R.-L. Chien, in: M. G. Khaledi, (Ed.), High Performance Capillary Electrophoresis (Theory, Techniques and Applications), Chapter 13, CRC Press, (1998).
[83] Z. Liu, P. Sam, S. R. Sirimanne, P. C. McClure, J. Grainger, D. G. Patterson, Field-amplified sample stacking in micellar electrokinetic chromatography for on-column sample concentration of neutral molecules, J. Chromatogr. A 673 (1994) 125.
[84] K. R. Nielson, J. P. Foley, Zone sharpening of neutral solutes in micellar electrokinetic chromatography with electrokinetic injection, J. Chromatogr. A 686 (1994) 283.
[85] J. P. Quirino, S. Terabe, On-line concentration of neutral analytes for micellar electrokinetic chromatography I. Normal stacking mode, J. Chromatogr. A 781 (1997) 119.
[86] C.-X. Zhang, W. Thormann, Head-column field-amplified sample stacking in binary system capillary electrophoresis. 2.optimization with a pre-injection plug and application to micellar electrokinetic chromatography, Anal. Chem. 70 (1998) 540.
[87] Z. K. Shihabi, Stacking of weakly cationic compounds by acetonitrile for capillary electrophoresis, J. Chromatogr. A 817 (1998) 25.
[88] J. Palmer, N. J. Munro, J. P. Landers, A universal concept for stacking neutral analytes in micellar capillary electrophoresis, Anal. Chem. 71 (1999) 1679.
[89] J. P. Quirino, S. Terabe, Approaching a million-fold sensitivity increase in capillary electrophoresis with direct ultraviolet detection: cation-selective exhaustive injection and sweeping, Anal. Chem. 72 (2000) 1023.
[90] J. P. Quirino, S. Terabe, Sweeping of analyte zones in electrokinetic chromatography, Anal. Chem. 71 (1999) 1638.
[91] J. P. Quirino, J.-B. Kim, S. Terabe, Sweeping: concentration mechanism and applications to high-sensitivity analysis in capillary electrophoresis, J. Chromatogr. A 357 (2002) 357.
[92] Y. Takagai, S. Igarashi, UV-detection capillary electrophoresis for benzo[a]pyrene and pyrene following a two-step concentration system using homogeneous liquid-liquid extraction and a sweeping method, Analyst 126 (2001) 551.
[93] M. R. N. Monton, J. P. Quirino, K. Otsuka, S. Terabe, Separation and on-line preconcentration by sweeping of charged analytes in electrokinetic chromatography with nonionic micelles, J. Chromatogr. A 939 (2001) 99.
[94] R. B. Taylor, R. G. Reid, A. S. Low, Analysis of proguanil and its metabolites by application of the sweeping technique in micellar electrokinetic chromatography, J. Chromatogr. A 916 (2001) 201.
[95] C. Fang, J.-T. Liu, C.-H. Lin, Optimization of the separation of lysergic acid diethylamide in urine by a sweeping technique using micellar electrokinetic chromatography, J. Chromatogr. B 775 (2002) 37.
[96] C. Fang, J.-T. Liu, C.-H. Lin, Determination of lysergic acid diethylamide (LSD) by application of on-line 77K fluorescence spectroscopy and a sweeping technique in micellar electrokinetic chromatography, Talanta 58 (2002) 691.
[97] M. J. Markuszewski, P. Britz-McKibbin, S. Terabe, K. Matsuda, T. Nishioka, Determination of pyridine and adenine nucleotide metabolites in Bacillus subtilis cell extract by sweeping borate complexation capillary electrophoresis, J. Chromatogr. A 989 (2003) 293.
[98] C.-H. Wu, M.-C. Chen, A.-K. Su, P.-Y. Shu, S.-H. Chou, C.-H. Lin, Determination of corticosterone in mouse plasma by a sweeping technique using micellar electrokinetic chromatography, J. Chromatogr. B 785 (2003) 317.
[99] M. R. N. Monton, K. Otsuka, S. Terabe, On-line sample preconcentration in micellar electrokinetic chromatography by sweeping with anionic-zwitterionic mixed micelles, J. Chromatogr. A 985 (2003) 435.
[100] J. P. Quirino, S. Terabe, Sample stacking of fast-moving anions in capillary zone electrophoresis with pH-suppressed electroosmotic flow, J. Chromatogr. A 850 (1999) 339.
[101] Z. K. Shihabi, Peptide stacking by acetonitrile-salt mixtures for capillary zone elecrophoresis, J. Chromatogr. A 744 (1996) 231.
[102] D. Martínez, F. Borrull, M. Calull, Sample stacking using field-amplified sample injection in capillary zone electrophoresis in the analysis of phenolic compounds, J. Chromatogr. A 788 (1997) 185.
[103] R. Kuldvee, M. Kaljurand, Stacking form the sample stream in CZE using a pneumatically driven computerized sampler, Anal. Chem. 70 (1998) 3695.
[104] Y. He, H.-K. Lee, Large-volume sample stacking in acidic buffer for analysis of small organic and inorganic anions by capillary electrophoresis, Anal. Chem. 71 (1999) 995.
[105] J. Palmer, J. P. Landers, Stacking neutral analytes in capillary electrokinetic chromatography with high-salt sample matrixes, Anal. Chem. 72 (2000) 1941.
[106] S. Locke, D. Figeys, Techniques for the optimization of proteomic strategies based on head column stacking capillary electrophoresis, Anal. Chem. 72 (2000) 2684.
[107] W.-H. Ding, C.-H. Liu, Analysis of linear alkylbenzenesulfonates by capillary zone electrophoresis with large-volume sample stacking, J. Chromatogr. A 929 (2001) 143.
[108] C.-X. Cao, Y.-Z. He, M. Li, Y.-T. Qian, M.-F. Gao, L.-H. Ge, S.-L. Zhou, L. Yang, Q.-S. Qu, Stacking ionizable analytes in a sample matrix with high salt by a transient miving chemical reaction boundary method in capillary zone electrophoresis, Anal. Chem. 74 (2002) 4167.
[109] J.-B. Kim, K. Otsuka, S. Terabe, Anion selective exhaustive injection-sweep-micellar electrokinetic chromatography, J. Chromatogr. A 932 (2001) 129.
[110] L. Zhu, H.-L. Lee, Field-amplified sample injection combined with water removal by electroosmotic flow pump in acidic buffer for analysis of phenoxy acid herbicides by capillary electrophoresis, Anal. Chem. 73 (2001) 3065.
[111] L. Zhu, C. Tu, H.-K. Lee, On-line concentration of acidic compounds by anion-selective exhaustive injection-sweeping micellar electrokinetic chromatography, Anal. Chem. 74 (2002) 5820.
[112] J. P. Quirino, U. Iwai, K. Otsuka, S. Terabe, Determination of environmentally relevant aromatic amines in the ppt levels by cation selective exhaustive injection-sweeping-micellar electrokinetic chromatography, Electrophoresis 21(14) (2000) 2899.
[113] O. Núñez, J.-B. Kim, E. Moyano, M. T. Galceran, S. Terabe, Analysis of the berbicides paraquat, diquat and difenzoquat in drinking water by micellar electrokinetic chromatography using sweeping and cation selective exhaustive injection, J. Chromatogr. A 961 (2002) 65.
[114] P. Britz-McKibbin, G. M. Bebault, D. D. Y. Chen, Velocity-difference induced focusing of nucleotides in capillary electrophoresis with a dynamic pH junction, Anal. Chem. 72 (2000) 1729.
[115] P. Britz-McKibbin, J. Wong, D. D. Y. Chen, Analysis of epinephrine from fifteen different dental anesthetic formulations by capillary electrophoresis, J. Chromatogr. A 853 (1999) 535.
[116] P. Britz-McKibbin, D. D. Y. Chen, Selective focusing of catecholamines and weakly acidic compounds by capillary electrophoresis using a dynamic pH junction, Anal. Chem. 72 (2000) 1242.
[117] W. Wei, G. Xue, E. S. Yeung, One-step concentration of analytes based on dynamic change in pH capillary zone electrophoresis, Anal. Chem. 74 (2002) 934.