Validation of an analytical method for the simultaneous determination of 16 drugs and metabolites in hair in the context of driving license granting

The use of psychoactive substances has been associated with increased risk for traffic accidents. Hair testing has become a routine practice in clinical and forensic toxicological laboratories, with a unique perspective in the investigation of drug consumption. The study aimed to develop and validate a UHPLC-MS/MS method for the determination of multiple drugs in hair, to be used for toxicological examination in driving license granting. Sample preparation was a one-step liquid extraction of milled hair with methanol, which was incubated for 15h at 50°C. The chromatographic separation was performed in a reversed phase column, with a run time of 2.2min. Measured compounds were cocaine, benzoylecgonine, norcocaine, anhydroecgonine methyl ester, cocaethylene, amphetamine, methamphetamine, methylenedioxyamphetamine, methylenedioxymethamphetamine, fenproporex, amfepramone, mazindol, codeine, morphine, 6-monoacetylmorphine, and tetrahydrocannabinol. The assay was linear for all substances (r>0.99), accurate (86.63-105.87 %), and precise, with a cv ranging from 1.9-13.5 % for intra-assay and 3.3-14.3 % for inter-assay. There was no significant carry over effect and the internal standard corrected matrix effect was minimal. The relative uncertainty percentages were below 9% for all the substances at cut-off values. The method was successfully applied to 50 hair samples from injured drivers, with 12% of positivity, including cocaine, MDMA and THC.