Liquid-phase microextraction and capillary electrophoresis of acidic drugs

\Vial liquid-phase microextraction (LPME) combined with capillary electroph oresis (CE) was evaluated for the determination of the acidic drugs ibuprof en, naproxen, and ketoprofen present in water samples and in human urine. T he 2.5 mt samples containing the drugs were filled into conventional vials and subsequently acidified by 250 mu L of 1-10 M HCl. Porous hollow fibers of polypropylene containing 25 mu L of an aqueous solution of 0.01-0.1 hn N aOH (acceptor solution) and with dihexyl ether immobilized in the pores of the wall were placed into each of the samples. The acidic drugs were extrac ted from the acidified sample solutions into the dihexyl ether phase, in th e pores of the hollow fiber, and further into the alkaline acceptor solutio n forced by high partition coefficients. The drugs were extracted almost qu antitatively (75-100% extraction efficiency) from the 2.5 mt samples and in to the 25 mu L acceptor solutions, providing 75-100 times preconcentration. The acceptor solutions were collected for automated CE analysis, which ena bled the drugs to be detected down to the 1 ng/mL level.