DETERMINATION OF PENICILLIN-G IN BEEF AND PORK TISSUES USING AN AUTOMATED LC CLEANUP

A procedure previously described for determination of beta-lactam anti biotics in milk was modified for use with tissues. Tissues were extrac ted directly with acetonitrile (procedure I) to avoid degradation of p enicillin G in water homogenates. Recovery of penicillin G in acetonit rile extracts of tissues was improved by addition of tetraethylammoniu m chloride and, in some cases, pH adjustment. The acetonitrile extract s were concentrated by evaporation and filtered. For cleanup, an autom ated high-performance liquid chromatography (HPLC) fractionation was u sed. The fraction corresponding to penicillin G was tested by a rapid screening test and, if positive, was analyzed by HPLC. For analysis, a n Inertsil ODS-2 column was used with a mobile phase of 0.0067 M KH2PO 4, 0.0033 M H3PO4-acetonitrile (68 + 32) with UV detection at 215 nm. For confirmation by treatment with beta-lactamase, tissues were homoge nized in water. An aliquot of the water homogenate was treated with be ta-lactamase prior to extraction with acetonitrile and tetraethylammon ium chloride (procedure II). Recoveries were 66-95% in the 0.1-1.0 ppm range, depending on the tissue, with a detection limit of about 5 ng/ g.