ENANTIOSELECTIVE DETERMINATION OF OXPRENOLOL IN HUMAN PLASMA USING DIALYSIS COUPLED ONLINE TO REVERSED-PHASE CHIRAL LIQUID-CHROMATOGRAPHY

A fully automated method for the determination of the enantiomers of o xprenolol in human plasma was developed, involving dialysis through a cellulose acetate membrane, clean-up and enrichment of the dialysate o n a short precolumn and subsequent chiral liquid chromatographic (LC) analysis. All sample handling operations were executed automatically b y a sample processor equipped with a robotic arm (ASTED system). The t race enrichment column (TEC) was packed with octadecylsilica. After co nditioning of the TEC with the LC mobile phase and pH 3.0 acetate buff er, the sample was dialysed in the static-pulsed mode. The donor and a cceptor solutions were made of pH 3.0 acetate buffer. After the enrich ment step, the analyte was transferred by the LC mobile phase to the a nalytical column by means of a switching valve. The influence of diffe rent parameters of the dialysis process on the recovery of oxprenolol was first investigated using achiral LC conditions. The volume as well as the aspirating and dispensing flow rates of the acceptor solution were the main parameters studied. Oxprenolol was separated on a C18 st ationary phase used for the enantioseparation of oxprenolol was a Chir alcel OD-R column which contained cellulose tris (3,5-dimethylphenylca rbamate) coated on silica as chiral selector. The corresponding mobile phase consisted of a mixture of pH 6.0 phosphate buffer containing Na ClO4 at 0.45 M concentration and acetonitrile (70:30 v/v). UV detectio n was performed at 273 nm. The method developed was validated. Recover ies for each enantiomer of oxprenolol were about 80%. The method was f ound to be linear in the 50-2500 ng ml(-1) concentration range (r(2) = 0.999 for both enantiomers) and good results with respect to intra- a nd inter-day reproducibility as well as accuracy were obtained. (C) 19 97 Elsevier Science B.V.