Determination of Sulfonamides in Commercial Veterinary Formulations by CE-MS/MS

A capillary electrophoresis tandem mass spectrometry (CE-MS/MS) method for the determination of four different sulfonamide antibiotics in commercial veterinary formulations has been developed. The samples were homogenized, solubilized in methanol, diluted in H2O/methanol (50:50, v/v), filtered, and injected, followed by electrophoretic separation in a polyvinyl alcohol (PVA)-coated capillary using a solution of 0.5 M acetic acid, pH 2.5 as background electrolyte (BGE). Calibration curves were constructed at six different concentrations, from 50 to 500 μg/L, and exhibited determination coefficients higher than 0.995 with limits of detection lower than 2.7 μg/L for all analytes. The proposed method was successfully applied to the determination of sulfamethazine, sulfamethizole, sulfachloropyridazine, and sulfadimethoxine concentration in commercial samples of veterinary formulations, with a separation time of less than 6.0 minutes. This high level of separation performance with sulfonamides is largely attributable to the powerful selective capability of the tandem mass detection (MS/MS) and PVA-coated capillary used, considering the similar electrophoretic mobility of these molecules.