Liquid-phase microextraction of drugs from human breast milk

Liquid-phase microextraction (LPME) based on disposable porous polypropylene hollow fibers was evaluated for the extraction of hydrophobic basic drugs from human breast milk. Direct LPME from breast milk samples provided low recoveries (18-38%) because the drugs were partially bound to the sample matrix (fat). Therefore, prior to extraction, the breast milk was acidified and the majority of fat was removed by centrifugation. The pH-reduction in the breast milk was performed to release drugs interacting with the matrix. From the supernatant, where pH was adjusted into the alkaline region with NaOH to deionize the analytes, the drugs were extracted through a thin layer of polyphenyl-methylsiloxane present in the pores of a porous hollow fiber and into 15 mul of 10 mM HCl as acceptor solution present inside the lumen of the hollow fiber. Subsequently, the acceptor solution was directly subjected to capillary electrophoresis (CE). For four antidepressant drugs, recoveries in the range 42-69% were obtained from breast milk, the drugs were enriched by a factor of 14-23 during LPME, excellent sample clean-up was observed, linearity (r > 0.99) was obtained in the range 50-500 ng/ml, and the extractions were found to be independent of the fat content in the breast milk samples. (C) 2003 Elsevier B.V. All rights reserved.