HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF PENICILLINS BY MEANS OF AUTOMATED SOLID-PHASE EXTRACTION AND PHOTOCHEMICAL DEGRADATION WITH ELECTROCHEMICAL DETECTION

An automated precolumn exchange system for on-line solid-phase extract ion (OPS-2) coupled to liquid chromatography with photochemical degrad ation and electrochemical detection was used for the determination of residual amounts of penicillin G, penicillin V, oxacillin, cloxacillin and dicloxacillin. A 5-10-fold increase in sensitivity was obtained w hen compared with direct UV detection of penicillins at 225 nm. The sy stem is recommended for samples that have received an immunoaffinity c lean-up. Analysis of bovine muscle tissue indicated, however, that thi s procedure could also be suitable for the determination of penicillin G at its maximum residue limit of 50 mu g/kg even with conventional s olvent partitioning for the first clean-up steps.