Liquid chromatography/tandem mass spectrometry for the qualitative and quantitative analysis of illicit drugs and medicines in preserved oral fluid.

A qualitative and quantitative analytical method was developed for the simultaneous determination of 24 illicit drugs and medicines, in preserved oral fluid samples collected with the StatSure Saliva Sampler collection device. The samples were prepared by liquid-liquid extraction followed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. The chromatographic separation was performed with an Atlantis T3 (100 x 2.1 mm i.d., 3 microm) reversed-phase column using an acetonitrile/2 mM ammonium formate buffer pH 3.4 gradient and the MS/MS detection was achieved with two precursor-product ion transitions per substance. The method was fully validated, including specificity and capacity of identification, limit of detection (0.2-2.1 microg/L), limit of quantitation (0.8-6.4 microg/L), recovery (34-98%), carryover, linearity (the method was linear in the range 1-200 microg/L), intra-assay precision (coefficient of variance (CV) <20% for 20 microg/L and CV <10% for 100 microg/L) and inter-assay accuracy (mean relative error <15%) and precision (CV <20%). The method showed to be specific and sensitive. It has already been successfully used in four proficiency tests and subsequently applied to oral fluid samples collected from road traffic volunteers in the driving population of Portugal (districts of Lisbon, Coimbra and Porto), within the DRUID project.