Determination of quinoxaline carboxylic acid (metabolite of carbadox) in animal tissue by HPLC.

A method for the determination of residues of quinoxaline-2-carboxylic acid (QCA), the major metabolite of carbadox, in pig kidney has been developed. Tissue samples were subjected to alkaline hydrolysis, liquid-liquid extractions, ion-exchange chromatography and further extraction to concentrate the analyte and purify the extract. Determination was by reverse phase HPLC with UV detection at 320 nm. Validation exercises carried out on batches of six samples fortified with 0.050 mg/kg QCA on three separate days gave mean recoveries ranging from 72 to 79% with relative standard deviations ranging from 5.6 to 7.8%. Samples fortified with 0.010 mg/kg QCA gave a mean recovery of 100% with a relative standard deviation of 9.8%.