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

Optimisation procedures originally applied to coupled-column RPLC-UV f or the residue analysis of polar pesticides were evaluated for the ana lysis of beta-agonists in human and bovine urine using direct sample i njection. Two approaches have been studied: (i) a multi-residue method (MRM) for the clean-up and separation of eight different beta-agonist s (isoprenaline, cimaterol, terbutaline, salbutamol, fenoterol, ractop amine, clenbuterol and mabuterol) and (ii) a single-residue method (SR M) focussed at the detection of clenbuterol residues in samples of uri ne. Both approaches provided efficient procedures to process urine sam ples automatically with coupled-column LC. Particular attention was pa id to selecting analytical conditions suitable for thermospray MS dete ction, which is to be investigated in the near future. Though UV detec tion cannot offer enough selectivity for the simultaneous screening of a group of p-agonists, coupled-column RPLC-UV proved to be very power ful 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 sampl e injection.