Quantitative analysis of sulfonamide residues in natural animal casings by HPLC

A multiresidue method has been developed for the simultaneous determination of sulfadiazine sulfathiazole, sulfapyridine, sulfamerazine, sulfamethoxydiazine, sulfamethylthiazole, sulfamethazine, sulfamonomethoxine, sulfamethoxypyridazine, sulfisoxazole, sulfamethoxazole sulfadimethoxine and sulfaquinoxaline in natural animal casings by HPLC after solid-phase extraction. The sulfonamides were extracted with acetonitrile and the extract cleaned up with an Oasis MCX SPE cartridge prior to analysis. Separation was on a ZOBAX Eclipse XDB-C-8 column using gradient elution with acetonitrile/methanol/0.1% acetic acid. The effect of separation conditions on chromatographic behavior and recovery has been studied. Calibration graphs were linear with very good correlation coefficients (r = 0.9983-0.9996) in the concentration range from 0.02 to 1 mu g mL(-1). The limits of quantitation (LOQ) for the 13 sulfonamides were in the range of 1.5-2.2 mu g kg(-1). Decision limits (CC alpha) and detection capabilities (CC beta) were in the range of 105.2-111.0 and 113.0-120.2 mu g kg(-1), respectively. The recovery for casings spiked with 1.5-100 mu g kg(-1) ranged from 65.2 to 85.9%. The relative standard deviations (RSDs) of the sulfonamides for six measurements at 100 mu g kg(-1) were from 2.2 to 7.7%. The applicability of the method to the analysis of salted swine casings, salted sheep casings and dry casing samples was demonstrated.