DETERMINATION OF PENICILLINS IN ANIMAL-TISSUES AT TRACE RESIDUE CONCENTRATIONS .2. DETERMINATION OF AMOXICILLIN AND AMPICILLIN IN LIVER ANDMUSCLE USING CATION-EXCHANGE AND POROUS GRAPHITIC CARBON SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A method for the determination of the basic penicillins, amoxicillin a nd ampicillin, in animal tissue is described The method used aqueous e xtraction with tungstate to remove proteins followed by cation exchang e solid phase extraction (SPF) clean-up. This extract was further puri fied using porous graphitic carbon (PGC) SPE. Extracted residues were derivatized with acetic anhydride followed by triazole/mercuric chlori de prior to reversed phase HPLC with UV determination at 325 nm. At th e Maximum Residue Limit of 50 mu g/kg in fortified cattle muscle valid ation gave mean recoveries for amoxicillin of 57% and 50% on two diffe rent days with relative standard deviations of 19% and 15% respectivel y. For ampicillin the recoveries were 72% and 59% with relative standa rd deviations of 15% and 19% respectively.