Application of capillary zone electrophoresis for analysis of thyreostatics

Capillary zone electrophoresis was optimized for the separation of thiouracil, methylthiouracil and propylthiouracil. Methylthiouracil could be determined in various types of urine (human, bovine, horse), either without any pretreatment or in ethyl acetate extracts, within 15 min. For identification, the simultaneous detection at three UV wavelengths (216, 245 and 278 nm) was advantageously used while for quantification the wavelength of the absorbance maximum at 278 nm was preferred. Under optimized conditions a linear response of the detector in the concentration range 0.1-100 ppm was obtained. On analysis of untreated urine, a detection limit of 0.5 ppm was found; for urine extracts the detection limit was 0.1 ppm. Univocal peak identification, based on absorption at three wavelength, was only possible above 2 ppm. Relative standard deviation for standard solutions of methylthiouracil, diluted in the background electrolyte, was 1%; for methylthiouracil in extracts dissolved in the background electrolyte it was 4.5%, and for methylthiouracil in untreated urine, 12.7%.