Validation of an LC-MS Method for the Detection and Quantification of BZP and TFMPP and their Hydroxylated Metabolites in Human Plasma and its Application to the Pharmacokinetic Study of TFMPP in Humans

An LC-MS method was developed for benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP), constituents of "party pills" or "legal herbal highs," and their metabolites in human blood plasma. Compounds were resolved using a mixture of ammonium formate (pH 4.5, 0.01 M) and acetonitrile (flow rate of 1.0 mL/min) with a C18 column. Calibration curves were linear from 1 to 50 ng/mL (R2 > 0.99); the lower limit of quantification (LLOQ) was 5 ng/mL; the accuracy was > 90%; the intra- and interday relative standard deviations (R.S.D) were < 5% and < 10%, respectively. Human plasma concentrations of TFMPP were measured in blood samples taken from healthy adults (n = 6) over 24 h following a 60-mg oral dose of TFMPP: these peaked at 24.10 ng/mL (+/- 1.8 ng/mL) (C(max)) after 90 min (T(max)). Plasma concentrations of 1-(3-trifluoromethyl-4-hydroxyphenyl) piperazine peaked at 20.2 ng/mL (+/- 4.6 ng/mL) after 90 min. TFMPP had two disposition phases (t(1/2) = 2.04 h (+/- 0.19 h) and 5.95 h (+/- 1.63 h). Apparent clearance (Cl/F) was 384 L/h (+/- 45 L/h).