Determination of timiperone in rat plasma by high-performance liquid chromatography with electrochemical detection

Recovery, enrichment and selectivity in liquid-phase microextraction comparison with conventional liquid-liquid extraction

Mathematical descriptions for extraction recovery and enrichment were applied for liquid-phase microextraction (LPME) and comparison with conventional two- and three-phase liquid-liquid extraction techniques (LLE) was made. The LPME theoretical calculations were verified by experimental determination of actual partition coefficients and by data obtained with LPME in a robust hollow fibre formate. With hollow fibre LPME operated in the two-phase mode, analytes were extracted from 1 to 4 ml aqueous samples into 25-50 microl of an organic solvent present in the pores and in the lumen of the porous hollow fibres. Compared with conventional two-phase LLE, two-phase LPME provided substantially higher enrichments for compounds with relatively large partition coefficients (K(org)/d>500). In contrast, because of the large volume of organic solvent relative to the sample volume, LLE provided high recovery and moderate enrichment even for compounds with relatively low partition coefficients (K(org)/d>5). Thus, two-phase LPME may be used for substantially enhanced extraction selectivity and enrichment of relatively hydrophobic analytes as compared with LLE whereas conventional two-phase LLE is superior for more hydrophilic analytes. Similar results were found for three-phase LPME where analytes where extracted from 1 to 4 ml aqueous samples through approximately 20 microl organic solvent immobilized within the pores of the hollow fibre and into 25 microl of an aqueous acceptor solution inside the lumen of the hollow fibre. The fundamental differences of LPME and LLE were further demonstrated with practical experiments on extraction of the basic drugs promethazine, methadone, and haloperidol from human plasma and urine.

Analyses of butyrophenones and their analogues in whole blood by high-performance liquid chromatography-electrospray tandem mass spectrometry

Five butyrophenones and two analogues contained in human whole blood have been analyzed by high-performance liquid chromatography (HPLC)-electrospray (ES)-tandem mass spectrometry (MS). All compounds gave the base peaks due to [M+1]+ by HPLC-ES-single MS. The product ions formed from each quasi-molecular ion by HPLC-ES-tandem MS showed the base peaks at m/z 165 for four compounds. The mass chromatography of HPLC-ES-tandem MS showed much higher sensitivity than that of HPLC-ES-single MS for all drugs spiked to whole blood. Therefore, regression equations, detection limits, recovery rates and precision were studied for haloperidol, bromperidol and fluoropipamide spiked to human whole blood by means of mass chromatography of HPLC-ES-tandem MS. The three compounds showed good linearity in the range of 0.2-0.8 ng/ml with a detection limit of about 0.1 ng/ml. Recoveries of the three compounds spiked to whole blood (0.2 and 0.8 ng added to 1 ml whole blood) were 23.6-81.2%; the coefficients of intra- and inter-day variations were 8.4-10.4 and 14.5-17.5%, respectively. The three compounds in whole blood could be actually determined 3 and 6 h after oral administration of 1 mg each of haloperidol and bromperidol, and 10 mg of floropipamide in a volunteer.