Simultaneous determination of sulfamethoxypyridazine, sulfamethoxazole, sulfadimethoxine and their associated compounds by liquid chromatography

A liquid chromatography method is described to determine sulfamethoxypyridazine (SMP), sulfamethoxazole (SMX), sulfadimethoxine (SDM), trimethoprim (TMP) and bromhexine (BRO) by using a Kromasil C18 column and 10 mM citrate buffer (pH 3.0)–methanol (from 31:69 to 69:31) as mobile phase in gradient mode. The mobile phase flow-rate and sample volume injected were 1 ml/min and 20 μl, respectively. The selected wavelength for the determination was 255 nm. The limits of quantification go from 200 μg/l for SDM to 1100 μg/l for BRO and the run time was 13 min. The method was applied in veterinary commercial formulations. Analytical results proved that some commercial claimed levels were not in agreement with the obtained results, as they were in other cases.