Carrier mediated transport solvent bar microextraction for preconcentration and determination of dexamethasone sodium phosphate in biological fluids and bovine milk samples using response surface methodology

In the current study, a fast and simple preconcentration and sample clean up procedure was developed based on carrier mediated three phase solvent bar liquid phase microextraction (TPSB-LPME) method prior to high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) absorbance detector for simultaneous extraction and determination of trace amounts of dexamethasone sodium phosphate (DSP) in human plasma, human urine and bovine milk. Accordihg to this procedure, dexamethasone sodium phosphate was extracted from an acidic aqueous sample (SP, 7.5 mL with pH = 6) into the organic solvent 1-octanol (containing 5%, w/v of Aliquat-336 as carrier) residing in the pores of a hollow fiber and then back extracted into an alkali receiving phase (RP, 5 mu L of 0.65 M NaClO4 with pH = 10) was located inside the lumen of the fiber. After the extraction period, the receiving phase was directly injected into HPLC. The effect of different extraction conditions (i.e., pH of source and receiving phases, ionic strength, stirring rate, counter-ion concentration and extraction time) on the extraction efficiency of DSP was investigated and optimized using central composite design (CCD) as a powerful tool. Under the optimal conditions, preconcentration factor of 320, extraction recovery of 23%, dynamic linear range of 1-1000 ng mL(-1) (r(2) = 0.997) and limit of detection of 0.1 ng mL(-1) were obtained. Eventually, applicability of the proposed method was successfully confirmed by extraction and determination of drug in plasma and urine samples and bovine milk with R.S.D.s < 8%. 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 the extraction process. This extraction technique is also the most economical sample preparation and preconcentration technique as compared to traditional extraction techniques. (C) 2013 Elsevier B.V. All rights reserved.