HPLC determination of residues of spectinomycin in various tissue types from husbandry animals†
An HPLC method was developed for the determination of bacteriostatic aminocyclitol spectinomycin (SP) in animal tissue products. These products included chicken eggs and edible fat, kidney, liver, muscle tissues from calf, poultry, pig and sheep. Residues of SP were extracted from homogenized tissue and egg-derived material with 25 mM citrate of pH 4.0, trichloroacetic acid and dichloromethane. The extract was purified and concentrated over a carboxylic acid-bonded solid-phase extraction (SPE) column. The SPE-eluate was analysed by cation-exchange HPLC involving a two-column switching system, post-column derivatization and fluorescence detection. Spectinomycin could be successfully determined at levels of 0.05 mg kg–1 and higher. Recoveries from spiked tissue material and from spiked egg material were in excess of 74% and did not show a concentration or tissue-type dependence. Precision of the elution position and signal response was better than 2%. Matrix effects and interference from lincomycin were less than 7 and 2%, respectively, on the signal response. Spectinomycin was shown to be stable at –20 °C in combined egg yolk and white over a test period of 12 weeks and in calf and sheep muscle tissue over a test period of 10 days. SP was, however, not stable at this temperature over a period of 12 months in chicken muscle tissue. Incurred SP residues were successfully determined in kidney and muscle tissue at the injection site of pigs administered with two doses of 15 mg kg–1 body weight SP with an intermittent withdrawal period of 15 days. Kidney showed higher concentrations and more persistent residues of SP than muscle tissue at the injection site.