Carrier mediated hollow fiber liquid phase microextraction combined with HPLC-UV for preconcentration and determination of some tetracycline antibiotics

In the present study, a simple and efficient preconcentration method was developed using carrier mediated three phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of trace amounts of highly hydrophilic tetracycline antibiotics including tetracycline (TCN), oxytetracycline (OTCN) and doxycycline (DCN) in bovine milk, human plasma and water samples. For extraction, 11.0 mL of the aqueous sample containing TCNs and 0.05 M Na2HPO4 (9.1 <= pH <= 9.5) was filled into a 12.0-mL vial. The solution of 1-octanol (containing 10% (w/v) of Aliquat-336 as carrier) was immobilized in the pores of a porous polypropylene hollow fiber. Aqueous receiving phase (RP, 24 mu L of 0.1 M H3PO4 and 1.0 M NaCl with pH = 1.6) was located inside the lumen of hollow fiber and the fiber was transferred into the aqueous sample. After the extraction period, the receiving phase was directly injected into HPLC. In order to obtain high extraction efficiency, the parameters affecting the liquid phase microextraction were evaluated and optimized. Under the optimized conditions, the calibration curves were linear in the range of 0.5-1000 mu g L-1 for TCN and OTCN, and in the range of 5-1000 mu g L-1 for DCN with good linearity (r(2) > 0.995). Finally, applicability of the proposed method was successfully confirmed by extraction and determination of the drugs in water and plasma samples as well as in bovine milk samples with low and high fat contents. Comparing to the traditional methods, the proposed method exhibits high sensitivity and high preconcentration factors as well as good precision. The extraction setup is simple and due to active transport of analytes. high cleanup effect and good selectivity are obtained in extraction process. (C) 2008 Elsevier B.V. All rights reserved.