Research Act (HRA) did not apply (Article 2.2. b). Aliquots of the samples were stored in the freezer at -20°C. Prior to analysis 100 µL of urine samples were thawed, spiked with 400 ng/ml IS (Cocaine-D3, Benzoylecgonine-D3, Tradamol-D3 and THC-D3) vortexed briefly and centrifuged for 10 min at 14000 rpm at 4°C.