High performance liquid chromatographic analysis of selected sulfonamides in plasma

Chromatographic conditions were elaborated to evaluate a model mixture of four sulfonamides (sulfamethoxazole, sulfamoxole, sulfisoxazole and sulfamethoxydiazine) in plasma using a reversed phase HPLC C18 column and a mobile phase composed of methanol and phosphate buffer (60:40; v/v) at pH 5.0. The detection was made using an electrochemical detection with the potential set at 1.1 V. In the case of sulfonamides deproteination of plasma with methanol was more advantageous than extraction with organic solvents. The recovery of analysed sulfonamides was in the range of 95-97%, the detection limits were 10 ng/ml of plasma.