Liquid chromatographic determination of six sulfonamide residues in animal tissues using postcolumn derivatization

A sensitive and reproducible liquid chromatographic method is described for the simultaneous determination of sulfonamide residues in animal livers and kidneys. The selectivity of the method is enhanced significantly through the use of postcolumn reaction with p-dimethylaminobenzaldehyde, followed by detection at 450 nm. Consequently, the cleanup is simplified; it consists of removal of fatty material by partitioning the sample extract into an acetonitrile-hexane system. The sulfonamides used for this study were sulfadiazine, sulfapyridine, sulfamerazine, sulfadimidine, sulfamethoxypyridazine, and sulfaquinoxaline. At the level of 100 micrograms/kg, the recoveries ranged from 70 to 104% and were dependent on the nature of the matrix and the particular sulfonamide. The coefficients of variation are 2-10% at this level. The detection limit was 20 micrograms/dg.