Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction-HPLC Determination of Low-Levels of Thiopental in Serum and Urine Samples

An ultrasound-assisted surfactant-enhanced emulsification microextra- ction (UASEME) coupled with high performance liquid chromatography-diode array detection has been developed for the extraction and determination of thiopental in serum and urine samples. A simple microextraction method based on emulsification of organic extraction solvent in aqueous sample using an ionic surfactant and without any organic solvent was evaluated for preconcentration and extraction of trace amounts of thiopental. The surfactant was used as carrier and disperser agent simultaneously. The analyte was converted into their ion-pair complexes with tetra butyl ammonium bromide and then extracted into an organic solvent (chloroform) dispersed in aqueous solution. Some parameters affect the extraction efficiency, such as the type and volume of the extraction solvent, the type and concentration of the surfactant, sample pH, the ultrasound emulsification time and salt addition. These parameters were investigated and optimized. Under optimum conditions, the limit of detection (LOD) and enrichment factor for this technique were 0.084 ng mL−1 and 174 respectively.