APPLICABILITY OF COUPLED-COLUMN LIQUID-CHROMATOGRAPHY TO THE ANALYSIS OF BETA-AGONISTS IN URINE BY DIRECT SAMPLE INJECTION .1. DEVELOPMENT OF A SINGLE-RESIDUE REVERSED-PHASE LIQUID-CHROMATOGRAPHY UV METHOD FOR CLENBUTEROL AND SELECTION OF CHROMATOGRAPHIC CONDITIONS SUITABLE FOR MULTI-RESIDUE ANALYSIS

Optimisation procedures originally applied to coupled-column RPLC-UV for the residue analysis of polar pesticides were evaluated for the analysis of beta-agonists in human and bovine urine using direct sample injection. Two approaches have been studied: (i) a multi-residue method (MRM) for the clean-up and separation of eight different beta-agonists (isoprenaline, cimaterol, terbutaline, salbutamol, fenoterol, ractopamine, clenbuterol and mabuterol) and (ii) a single-residue method (SRM) focussed at the detection of clenbuterol residues in samples of urine. Both approaches provided efficient procedures to process urine samples automatically with coupled-column LC. Particular attention was paid to selecting analytical conditions suitable for thermospray MS detection, which is to be investigated in the near future. Though UV detection cannot offer enough selectivity for the simultaneous screening of a group of p-agonists, coupled-column RPLC-UV proved to be very powerful in SRM, allowing the detection of clenbuterol at the mu g/l level in filtered (0.35 0.45 mu m) human and bovine urine after direct sample injection.