RESUMO
Two simple and reliable methods are described for the determination of sulphaquinoxaline [SQX] and amprolium [AMP] combined in veterinary powder. The first method depends on high performance liquid chromatography on a reversed phase column [micro. Bondapak-C[18]] using mobile phase consisting of acetonitrile-methanol-water-phosphoric acid [30: 5: 55: 0.7, by volumes] at a flow rate of 1 ml min[-1] with UV detection at 254 nm. The detection limits were 0.2 micro,g ml[1] and 0.35 micro g ml' and linearity ranges were 2-20].micro g ml and 4-40[.micro g ml for SQX and AMP, respectively. The second one deals with the first derivative ['D] spectrophotometry with zero-crossing measurment at 253 nm and 226 nm for SQX and AMP respectively. The detection limits were 0.3 micro.g ml and 1.2 micro g ml[1] and linearity ranges were 1 -18 micro,g ml1 and 4-32 micro.g ml1 for SQX and AMP, respectively, the proposed procedures were successfully applied to the determination of these drugs in laboratory prepared mixtures with mean percentage recovery ranged from 98.50 to 99.75 and in commercial preparation ranged from 103.85 to 104.85