Résumé
Three new accurate and sensitive methods were developed for the determination of two veterinary drugs. Florfenicol was analyzed by a stability-indicating TLC/densitometric method in presence of its amine degradation product obtained via acid hydrolysis. It was based on the difference in Rf values of the drug and its degradation product at 254 nm on silica gel 60 GF254 plates using chloroform–methanol (7:3 v/v) as developing solvent (Method A). However, buparvaquone was analyzed through reduction with NaBH4 in methanolto yielda red colored product measured spectrophotometrically at 489 nm (Method B). This reduction product was also measured spectrofluorometrically at 450 nm after excitation at 334 nm (Method C). Good linearity was obtained in the range of 10-100 μg/spot for florfenicol in method A and 10-120 or 0.3-2.4 μg mL-1 for buparvaquone by methods B and C with mean accuracy of 99.94%±0.89, 99.99%±0.99 or 99.66%±1.80, respectively. The densitometric method A proved to be stability-indicating in presence of 10-90% of buparvaquone amine degradation product. The three proposed methods were validated according to ICH guidelines and successfully applied for the assay of the cited drugs in their pharmaceutical formulations.