Determination of pharmaceutical and illicit drugs in oral fluid by ultra-high performance liquid chromatography–tandem mass spectrometry

A simple and extremely fast procedure for the quantitative determination in oral fluid samples of 44 substances, including the most common drugs of abuse and several pharmaceutical drugs, was developed and fully validated. Preliminary sample treatment was limited to protein precipitation. The resulting acetonitrile solution was directly injected into an ultra-high performance liquid chromatograph (UHPLC) equipped with a C18 column (100 mm × 2.1 mm, 1.7 μm). The mobile phase eluted with linear gradient (water/formic acid 5 mM: acetonitrile/formic acid 5 mM; v:v) from 98:2 to 0:100 in 5.0 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 9.0 min including re-equilibration at the initial conditions. The analytes were revealed by a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The method proved to be simple, accurate, rapid and highly sensitive, allowing the simultaneous detection of all compounds. The ease of sample treatment, together with the wide range of detectable substances, all with remarkable analytical sensitivity, make this procedure ideal for the screening of large populations in several forensic and clinical contexts, whenever oral fluid sampling has to be preferred to blood sampling, as for example in short retrospective investigations.