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KeyWordsColumn liquid chromatography Solid-phase-extraction Penicillin varieties Calf and pig serum SummaryAn HPLC method was developed for determination of amoxicillin, penicillin G, penicillin V, ampicillin, oxacillin, cloxacillin, nafcillin and dicloxacilhn in serum from pigs and cattle. Serum was cleaned up by solid-phase extraction (SPE), ultra-filtered and derivatised. The method was linear in the range tested up to 2000 ng mL-1 of individual penicillins in serum. Limits of detection were 11 -14 ng mL -1. Mean recoveries were 90-103% in the range 20-2000 ng mL -1. The relative repeatability, standard deviation was < 10% at 20 ng mL -1 level and < 6% in the range 100 -2000 ng mL -1.

A liquid chromatographic (LC) method based on solid-phase extraction was developed for determination of amoxicillin in muscle tissue of rainbow trout. The compound was extracted in an aqueous solution by precipitation of organic material with a mixture of sulfuric acid and sodium tungstate. The extract was processed by solid-phase extraction on an end-capped phenyl sorbent, and concentrated on a divinylbenzene-co-ΛN-vinylpyrrolidone polymeric sorbent. The extract was derivatized and analyzed by reversed-phase gradient LC on a C18 column with UV detection at 323 nm. The method detection limit was 2.9 μg/kg. Mean recovery in muscle was 80.5% (range 10-200 μg/kg). The method was applied to fillets from trout offered feed containing amoxicillin in an aquaculture pilot plant. Amoxicillin was detected in muscle tissue shortly after administration but not 3 weeks later. The relative repeatability standard deviation for incurred residues in muscle tissue was 6.4% (range 11-143 μg/kg).