Micelle-Mediated Extraction and its Application to Capillary Electrophoresis. Simultaneous Determination of Active Compounds in Pharmaceutical Samples

GOMEZ, MARÍA ROXANA; SOMBRA, LORENA; MARTINEZ, LUIS DANTE; SILVA MARÍA F.

Simposio; 8vo Simposio Latinoamericano en Aplicaciones de la Electroforesis Capilar y Tecnología del Microchip en Biotecnología, Biomedicina, Biofarmacia e Industria (LACE 2002); 2002

The feasibility of employing micelle-mediated extraction as an alternative and effective method for the solubilization, purification and/or preconcentration of active ingredients from pharmaceutical preparations was studied. The use of cloud-point extraction (CPE) eliminates most of these sample clean-up problems and allows the determination of the analytes at trace levels. The potential of the CPE methodology for the preconcentration of several pharmaceutical compounds was studied using the non-ionic surfactants of the polyoxyethylene nonyl phenyl ethers family (PONPE 5, PONPE 7.5 and PONPE 10), and the t-Octylphenoxy ?polyoxyethylene ethers family (TX-114, TX-100, TX-405 and Igepal). The test mixtures under investigation were different combinations of the following analytes: paracetamol, caffeine, ibuprofen, sulphamethoxazole, trimethroprim, theophylline, and major active components in St. John?s Wort. The preconcentration of these compounds was obtained by CPE under optimum conditions of pH, surfactant type, and concentration. The amount of surfactant used is a critical variable in the preconcentration factor because it determines the extraction yield and the volume of surfactant-rich phase obtained. These values were determined as a function of the surfactant concentration, together with the phase volume ratio, which allows prediction of the maximum preconcentration factor under given conditions. The separation of the active ingredients in pharmaceutical formulations by micellar electrokinetic capillary chromatography (MEKC) and capillary zone electrophoresis (CZE) with direct absorptiometric detection was investigated. The type and composition of the background electrolytes (BGE) were investigated with respect to separation selectivity and BGE stability. All parameters affecting the analytical performance of the methodology were evaluated and optimized.