Determination of Phenolic Acids in Herba Epilobi by ITP–CE in the Column-Coupling Configuration |
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Authors: | J ?afra M Pospí?ilová J Spilková |
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Institution: | (1) Faculty of Pharmacy in Hradec Králové, Department of Analytical Chemistry, Charles University in Prague, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic;(2) Faculty of Pharmacy in Hradec Králové, Department of Farmacognosy, Charles University in Prague, Heyrovského 1203, 500 05 Hradec Králové, Czech Republic |
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Abstract: | The combination of capillary isotachophoresis (ITP) and capillary zone electrophoresis (CZE) in the column-coupling configuration
has been optimized in a mode in which the background electrolyte employed in the CZE step was different from the leading and
terminating electrolytes of the ITP step. The optimum composition of the electrolyte system was 0.01 M HCl, 0.02 M IMI, 0.2%
HEC, pH 7.2 (leading electrolyte), 0.01 M HEPES, pH 8.2 (terminating electrolyte), and 25 mM MES, 50 mM TRIS, 30 mM boric
acid, 0.2% HEC, pH 8.3 (background electrolyte). All solutions contained 20% methanol. The timing of the transfer of isotachophoretically
stacked analyte zones into the CZE column was also optimized. An ITP–CZE method with UV detection at 270 nm was developed
for separation of nine phenolic acids (protocatechuic, syringic, vanillic, cinnamic, ferulic, caffeic, ρ-coumaric, chlorogenic, and gentisic acids) in a model mixture and used for assay of some of these acids in a methanolic extract
of herba epilobi. Application of ITP–CZE resulted in 100-fold better sensitivity than conventional CZE; limits of detection
ranged between 10 and 60 ng mL−1. When MES–TRIS–borate-based buffer, pH 8.3, was used in the CZE separation step the linearity of the ITP–CZE response was
satisfactory (correlation coefficients were from 0.9937 to 0.9777). Repeatability was also satisfactory (RSD values ranged
between 0.77% and 1.28% for migration times and between 1.65% and 13.69% for peak area).
Revised: 23 March and 27 April 2006 |
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Keywords: | Capillary isotachophoresis Zone electrophoresis Phenolic acids Plant extract Epilobium |
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