Improvement of chemical analysis of antibiotics. XVI. Simple and rapid determination of residual pyridonecarboxylic acid antibacterials in fish using a prepacked amino cartridge.

A simple and rapid method for the determination of residual pyridonecarboxylic acid antibacterials (PCAs) (oxolinic acid, nalidixic acid and piromidic acid) in fish was developed using a combination of high-performance liquid chromatography (HPLC) and clean-up with an amino-type prepacked cartridge. PCAs were extracted with n-hexane-ethyl acetate (1:3) and the extract was applied to a Baker 10 amino cartridge. PCAs were eluted from the cartridge with acetonitrile-methanol-0.01 M aqueous oxalic acid solution (pH 3.0) (3:1:6) and were determined by HPLC. The separations were performed on Nucleosil 3C18 (3 microns, 75 x 4.6 mm I.D.) using a mobile phase containing oxalic acid. The recoveries of PCAs from various fishes fortified at the level of 1.0 ppm were 77.1-95.5%, and the detection limits were 0.05 ppm. The analytical time per sample was less than 30 min.