Development of multi-residue methodology for the HPLC determination of veterinary drugs in animal tissues

The application of solid-phase extraction and HPLC with UV-diode array detection to the multi-residue determination of veterinary drugs is described. A two-stage SPE clean-up was employed, using C18 and silica cartridges. HPLC analysis was carried out on a base-deactivated C8 column using gradient elution systems at two pH values. The procedure establishes the basis of a method for routine screening of pig kidney samples for some sulphonamides, benzimidazoles, nitroimidazoles and nitrofurans at concentrations at or below the UK Maximum Residue Limits (MRLs). Limits of detection of 2-18 micrograms/kg could be achieved for these analytes at recoveries of 40-70%. UV spectra measured on-line were used for confirmation of peak identities at these concentrations. The possibility of extension of this procedure to a wider range of analyses is discussed.