ONLINE POSTCOLUMN PHOTOCHEMICAL DERIVATIZATION IN LIQUID CHROMATOGRAPHIC-DIODE-ARRAY DETECTION ANALYSIS OF BINARY DRUG MIXTURES

HPLC methods were developed for the analysis of pharmaceutical creams containing binary drug mixtures (betamethasone valerate-chlorocresol; hydrocortisone-miconazole nitrate; desonide pivalate-chlorhexidine; de xamethasone-clolrimazole; triamcinolone acetonide-econazole nitrate). The chromatographic separations were performed on C-18 and cyano colum ns under reversed-phase conditions. A post-column on-line photochemica l reactor (irradiation at 254 nm) was arranged between the analytical column and the diode-array detector to enhance the performance of the method. Two UV spectra (photoreactor on and off) were obtained for eac h analyte and these additional sources of information proved to be use ful for the unambiguous identification of the various analytes. The me thod was applied to the quality control of commercial creams using a s olid-phase extraction procedure for the sample clean-up.