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A method for clenbuterol residue analysis in urine and animal tissues has been developed. The detection limits are 0.25 micrograms/l and 0.5 micrograms/kg, respectively. The recovery in urine varies from 85% to 90% and in animal tissues from 70% to 74%. The beta 2-agonist was liberated from the tissues by an enzymatic digestion, purified on Chem Elut columns using alkaline conditions and extracted with 0.01 mol/l HCl. Clenbuterol was quantified by high-performance liquid chromatography (HPLC) on a RP-8 column and a post-column reaction procedure. High-performance thin-layer chromatography (HPTLC) was performed on silica gel 60 plates and clenbuterol visualized by means of the modified Ehrlich's TLC spray reagent. Since this method is sensitive, as is HPLC, it was used to obtain a confirmation and to exclude false positive results.

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An HPLC method for the analysis of levamisole and thiabendazole has been developed with recoveries varying over 63-75%. The two anthelmintics are extracted from meat with ethyl acetate, purified by liquid/liquid extraction and analyzed quantitatively on a mu Bondapak C18 column. The optimum detection is achieved by means of a photodiode array detector at 240 nm for levamisole and at 300 nm for thiabendazole. The detection limits for both compounds in meat are 25 micrograms/kg and 5 micrograms/kg, respectively.