RESUMEN
An automated precolumn exchange system for on-line solid-phase extraction (OPS-2) coupled to liquid chromatography with photochemical degradation 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 when compared with direct UV detection of penicillins at 225 nm. The system is recommended for samples that have received an immunoaffinity clean-up. Analysis of bovine muscle tissue indicated, however, that this procedure could also be suitable for the determination of penicillin G at its maximum residue limit of 50 micrograms/kg even with conventional solvent partitioning for the first clean-up steps.
Asunto(s)
Penicilinas/análisis , Animales , Autoanálisis , Bovinos , Cromatografía Líquida de Alta Presión , Electroquímica , Músculo Esquelético/química , Oxidación-Reducción , Penicilinas/química , Fotoquímica , Solventes , Espectrofotometría UltravioletaRESUMEN
A high-performance liquid chromatographic (HPLC) method with automated cleanup by on-line solid phase extraction was developed for the determination of oxacillin, cloxacillin and dicloxacillin in bovine muscle tissue. The penicillins were extracted from the matrix with acetonitrile, transferred to phosphate buffer and automatically trapped on a RP-18 solid phase extraction column. After on-line elution onto the analytical HPLC-column, penicillins were quantified by UV (lambda = 225 nm) after isocratic separation. Mean recoveries at the MRL (0.3 mg/kg) were 92% for oxacillin, 92% for cloxacillin and 86% for dicloxacillin. The coefficients of variation for the three penicillins in the range of 0.15-0.6 mg/kg were 13.8%, 11.0%, and 7.3%, respectively. The applicability of this method for the determination of cloxacillin in milk was demonstrated.