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Thirty-five different basic drugs were extracted by electro membrane extraction (EME), from acidified samples containing HCl as the BGE, through an organic solvent immobilized in the pores in the wall of a porous hollow fiber (supported liquid membrane, SLM), and into an acidified acceptor solution (HCl) in the lumen of the hollow fiber by the application of an electrical potential difference of 50 V. With 2-nitrophenyl pentyl ether (NPPE) as the SLM, and with 10 mM HCl as BGE in the sample and acceptor solution, singly charged basic drugs with log P >2 were extracted with recoveries in the range 30-81% within 5 min. For doubly charged basic drugs, extraction was effectively enhanced by decreasing the concentration of HCl in the sample from 10 to 0.1 mM, reducing the ionization of the analytes. For medium polar analytes (1 < log P < 2), an ion balance of 0.01 was combined with addition of tris-(2-ethylhexyl) phosphate (TEHP) to the SLM, and this provided recoveries in the range 36-70%. The ion balance was defined as the concentration ratio of BGE between the sample and the acceptor solution. For the most polar drugs (log P <1), EME was accomplished with an ion balance of 0.01 and with di-(2-ethylhexyl) phosphate (DEHP) added to the SLM, but in spite of this, recoveries were in the range of only 4-17%.

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The present work describes the first systematic study of electromembrane extraction (EME) from biological matrices under physiological conditions. Six basic drugs with protein binding in the range of 20-97% were extracted from untreated human plasma and whole blood through a supported liquid membrane (SLM) consisting of 1-ethyl-2-nitrobenzene impregnated in the walls of a hollow fiber, and into an acidified aqueous solution inside the lumen of the fiber. The electrical potential difference over the membrane reduced the protein binding of the drugs and transported the free drug fraction over the membrane. Recoveries in the range 25-65% were obtained with 10-min extraction time and an applied voltage of only 10 V over the SLM. Interday precision better than 20% RSD and linearity in the range 0.5-10 microg/mL were obtained for nortriptyline and methadone. Extraction from untreated whole blood was also demonstrated with recoveries in the range 19-51%.

In this work, a single-well electromembrane extraction (EME) device was developed based on a thin (100μm) and flat porous membrane of polypropylene supporting a liquid membrane. The new EME device was operated with a relatively large acceptor solution volume to promote a high recovery. Using this EME device, exhaustive extraction of the basic drugs quetiapine, citalopram, amitriptyline, methadone and sertraline was investigated from both acidified water samples and human plasma. The volume of acceptor solution, extraction time, and extraction voltage were found to be important factors for obtaining exhaustive extraction. 2-Nitrophenyl octyl ether was selected as the optimal organic solvent for the supported liquid membrane. From spiked acidified water samples (600μl), EME was carried out with 600μl of 20mM HCOOH as acceptor solution for 15min and with an extraction voltage of 250V. Under these conditions, extraction recoveries were in the range 89-112%. From human plasma samples (600μl), EME was carried out with 600μl of 20mM HCOOH as acceptor solution for 30min and with an extraction voltage of 300V. Under these conditions, extraction recoveries were in the range of 83-105%. When combined with LC-MS, the new EME device provided linearity in the range 10-1000ng/ml for all analytes (R(2)>0.990). The repeatability at low (10ng/ml), medium (100ng/ml), and high (1000ng/ml) concentration level for all five analytes were less than 10% (RSD). The limits of quantification (S/N=10) were found to be in the range 0.7-6.4ng/ml.