Simultaneous determination in hair of multiclass drugs of abuse (including THC) by ultrahigh performance liquid chromatography - tandem mass spectrometry

A simple procedure for the quantitative determination in hair samples of 13 common drugs of abuse or metabolites (morphine, 6-acetylmorphine, codeine, amphetamine, methamphetamine, 3,4- methylenedioxy-amphetamine, 3,4-methylenedioxymethamphetamine, 3,4- methylenedioxyethylamphetamine, benzoylecgonine, cocaine, buprenorphine, methadone and 9- tetrahydrocannabinol) has been developed and fully validated. The analytes were extracted from the matrix by a simple overnight incubation with methanol at 55°C. An aliquot of the extract was directly injected into an ultra-high performance liquid chromatography system equipped with Waters Acquity UHPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm). The mobile phase eluted with a linear gradient (water/formic acid 5mM : acetonitrile; v:v) from 98:2 to 0:100 in 4.5 min, followed by isocratic elution at 100% B for 1.0 min. The flow rate was 0.6 mL/min and the total run time was 8.0 min including re-equilibration at the initial conditions. The compounds were revealed by a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The absence of matrix interferents, together with excellent repeatability of both retention times and relative abundances of diagnostic transitions, allowed the correct identification of all analytes tested. The method proved linear in the interval from the limit of quantification to 5.0 ng/mg (1.0 ng/mg for 9-tetrahydrocannabinol) with correlation coefficient values ranging from 0.9970 to 0.9997. Quantitation limits were below the cut-off values recommended by the Society of Hair Testing and ranged from 0.02 to 0.08 ng/mg. Application of the present UHPLC-MS/MS procedure and instrumentation to hair analysis allows high sample-throughput, together with excellent sensitivity and selectivity, in workplace drug-screening controls and forensic investigations. These qualities, combined with minimal sample workup, make the cost of this screening affordable for most private and public administrations.