Akesolo U, Maguregui M I, González L, Jiménez R M, Alonso R M
Departamento de Química Analítica, Facultad de Ciencias, Universidad del País Vasco, Apdo. 644, 48080 Bilbao, Spain.
J Chromatogr Sci. 2004 Feb;42(2):74-9. doi: 10.1093/chromsci/42.2.74.
Experimental design methodologies are applied to the development of a capillary zone electrophoretic method for the separation of the angiotensin-converting enzyme inhibitor enalapril and its derivative enalaprilat and the diuretics xipamide and hydrochlorothiazide. The effects of pH, buffer concentration, proportion of boric acid in the mixed boric acid-potassium dihydrogen phosphate background electrolyte, temperature, applied voltage, and percentage of organic modifier are studied. Critical factors are identified in a screening design (a 2(6-2) fractional factorial design), and afterwards, optimal conditions for the separation are reached by means of an optimization design (a 2(2) + 2 x 2 + k central composite design). The studied response is the resolution between peaks. The four studied compounds can be separated in less than 3.5 min using an electrolyte of 20mM boric acid-potassium dihydrogen phosphate (75:25, v/v) with 5% MeOH adjusted to pH 8.0 with KOH, at a potential of 30 kV. The detection wavelength and temperature are 206 nm and 35 degrees C, respectively.
