High performance liquid chromatography/electrospray tandem mass spectrometry for phenothiazines with heavy side chains in whole blood.

Eleven phenothiazine derivatives with heavy side chains 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 due to side chains liberated. The mass chromatography of HPLC/ES tandem MS showed much higher sensitivity than that of HPLC/ES single MS for phenothiazines spiked to whole blood. Therefore, regression equations, detection limits, recovery rates and reproducibility were studied for thiethylperazine, clospirazine and flupentixol 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 2-40 ng/mL with a detection limit of about 0.5 ng/mL. Recoveries of the three compounds spiked to whole blood (2 and 8 ng added to 1 mL whole blood) were 43.4-72.5 %; the coefficients of intraday and interday variations were 3.7-9.3 and 12.6-17.9 %, respectively. Thiethylperazine, clospirazine and flupentixol in whole blood could actually be determined with sufficient sensitivity 3 and 6 h after oral administration of 5-10 mg of each compound in a volunteer.