title: Quantitative aspects of microchip isotachophoresis for high precision determination of main components in pharmaceuticals.
abstract: Although microchip electrophoresis (MCE) is intended to provide reliable quantitative data, so far there is only limited attention paid to these important aspects. This study gives a general overview of key aspects to be followed to reach high-precise determination using isotachophoresis (ITP) on the microchip with conductivity detection. From the application point of view, the procedure for the determination of acetate, a main component in the pharmaceutical preparation buserelin acetate, was developed. Our results document that run-to-run fluctuations in the sample injection volume limit the reproducibility of quantitation based on the external calibration. The use of a suitable internal standard (succinate in this study) improved the repeatability of the precision of acetate determination from six to eight times. The robustness of the procedure was studied in terms of impact of fluctuations in various experimental parameters (driving current, concentration of the leading ions, pH of the leading electrolyte and buffer impurities) on the precision of the ITP determination. The use of computer simulation programs provided means to assess the ITP experiments using well-defined theoretical models. A long-term validity of the calibration curves on two microchips and two MCE equipments was verified. This favors ITP over other microchip electrophoresis techniques, when chip-to-chip or equipment-to-equipment transfer of the analytical method is required. The recovery values in the range of 98-101 % indicate very accurate determination of acetate in buserelin acetate, which is used in the treatment of hormone-dependent tumors. This study showed that microchip ITP is suitable for reliable determination of main components in pharmaceutical preparations.
authors: Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 84215, Bratislava, Slovak Republic.
authors: Jasna
authors: J
authors: Hradski
authors: Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 84215, Bratislava, Slovak Republic.
authors: Mária Drusková
authors: MD
authors: Chorváthová
authors: Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 84215, Bratislava, Slovak Republic.
authors: Róbert
authors: R
authors: Bodor
authors: Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynská dolina F2, 84248, Bratislava, Slovak Republic.
authors: Martin
authors: M
authors: Sabo
authors: Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynská dolina F2, 84248, Bratislava, Slovak Republic.
authors: Štefan
authors: Š
authors: Matejčík
authors: Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 84215, Bratislava, Slovak Republic. masar@fns.uniba.sk.
authors: Marián
authors: M
authors: Masár
mesh_terms: D000085:Acetates / Q000302:isolation & purification*; D002064:Buserelin / Q000032:analysis*; D002138:Calibration; D003198:Computer Simulation; D004553:Electric Conductivity; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D005300:Fertility Agents, Female / Q000032:analysis*; D017022:Flow Injection Analysis / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057625:Isotachophoresis / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D015233:Models, Statistical; D012015:Reference Standards; D015203:Reproducibility of Results; D019802:Succinic Acid / Q000302:isolation & purification
chemical_list: D000085:Acetates; D005300:Fertility Agents, Female; D019802:Succinic Acid; D002064:Buserelin
keywords: Buserelin acetate; Conductivity detection; Counterion; Microchip isotachophoresis; Quantitative analysis