The selected drugs of abuse and cannabinoids were spiked into a pooled urine sample to evaluate the assay performance. The internal standards cocaine-D3, tramadol-D3 and THC-D3 were used to correct matrix effect and losses in sample preparation. For all DoA compounds, the assay response was found to be linear over more of three orders of magnitude, ranging from 5 to 10000 ng/ml. Precision and accuracy were determined at four levels LLOQ (5 ng/ml), LQC (15 ng/ml), MQC (3800 ng/ml) and HQC (7500 ng/ml) for short LC-vDMS-SIM/MS (See Table ) and LC-MRM/MS (See Table ).