A gas chromatographic mass spectrometric assay for plasma trifluoperazine concentrations following single doses

A gas chromatography mass spectrometric assay using selected ion monitoring is described which permits the determination of trifluoperazine in plasma at concentrations ranging from 0.078 to 5.0 ng ml-1. It relies on the extraction of trifluoperazine and the internal standard, prochlorperazine or the tetradeuterated analogue of trifluoperazine, from basified plasma with a n-pentane/2-propanol solvent mixture. Following the evaporation of organic solvent, the residue is reconstituted in a small volume of methanol. Suitable aliquots were analysed by the combined technique of gas chromatography/electron impact mass spectrometry with a data system. The described procedure is specific and enables the quantitation of 78 pg ml-1 of the drug with a coefficient of variation less than 7%. The method has demonstrated sufficient sensitivity to permit pharmacokinetic and bioavailability studies after a single 5 mg oral dose.