Detection of phencyclidine in human oral fluid using solid-phase extraction and liquid chromatography with tandem mass spectrometric detection

An analytical procedure for the determination of phencyclidine in oral fluid has been developed and validated using liquid chromatography with tandem mass spectral detection, following initial screening with enzyme linked immunosorbent assay. The oral fluid samples were collected using the Quantisal ™ device, and any drugs present were quantified using mixed mode solid-phase extraction followed by mass spectrometric detection in positive atmospheric pressure chemical ionization mode. For confirmation, two transitions were monitored and one ratio determined, which had to be within 20% of that of the known calibration standard. The monitoring of the qualifying transition and requirement for its presence within a specific ratio to the primary ion has the potential of limiting the sensitivity of the assay, however, the additional confidence in the final result as well as forensic defensibility were considered to be of greater importance. The limit of quantitation was 5 ng/mL; the intra-day precision of the assay (n = 5) was 3.04%; inter-day precision 3.35% (n = 5) at a concentration of 10 ng/mL. The accuracy was determined at four concentrations (5, 10, 20 and 40 ng/mL) within the linear range of the assay. The percentage recovery of phencyclidine from the oral fluid collection pad was 81.7% (n = 6). The methods were applied to both proficiency specimens and to samples obtained during research studies in the USA.