Simultaneous determination of seven penicillins in muscle, liver and kidney tissues from cattle and pigs by a multiresidue high-performance liquid chromatographic method

A high-performance liquid chromatographic (HPLC) method based on solid-phase extraction (SPE) was developed for determination of amoxicillin, penicillin G (benzylpenicillin), ampicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in muscle, liver and kidney tissues of pigs and cattle. The compounds were extracted in aqueous solution by precipitation of organic materials with a mixture of sulphuric acid and sodium tungstate. The extract was cleaned up by SPE on a divinylbenzene-co-N-vinylpyrrolidone polymeric sorbent. Further clean-up was performed by liquid-liquid partition with diethyl ether. The extract was derivatised with benzoic anhydride and 1,2,4-triazole mercury (LT) reagent. Chromatography was performed by reversed-phase gradient HPLC on a C-18 column with ultraviolet detection at 323 nm. The limits of detection estimated by a conservative model were in the range 8.9-11.1 mu g/kg for amoxicillin, penicillin G, ampicillin, oxacillin, cloxacillin and nafcillin and 18.3-20.9 mu g/kg for dicloxacillin. The mean recovery range was 66-77% for amoxicillin, 73-75% for penicillin G, 81-82% for ampicillin, 73-76% for oxacillin, 74-75% for cloxacillin, 66-72% for nafcillin and 58-65% for dicloxacillin. (C) 1999 Elsevier Science B.V. All rights reserved.