Hollow-fiber liquid-phase microextraction and chiral LC-MS/MS analysis of venlafaxine and its metabolites in plasma.

An enantioselective analytical method was developed and validated for determination of venlafaxine and its metabolites O-desmethylvenlafaxine and N-desmethylvenlafaxine in plasma samples. The method employed LC-MS/MS analysis and hollow-fiber liquid-phase microextraction (HF LPME) for sample preparation. After HF LPME optimization the following condition was established: sample volume of 4 ml, sample agitation at 1750 rpm, 20 min of extraction, 0.1 mol/l acetic acid as acceptor phase, 1-octanol as organic phase and donor phase pH adjustment to 10. Under these conditions, the method was linear over the concentration range of 5-500 ng/ml with quantification limits of 5 ng/ml. The use of HF LPME for sample preparation provided suitable recoveries, efficient clean-up and low consumption of organic solvent.