Rapid screening of drugs of abuse in human urine by high-performance liquid chromatography coupled with high resolution and high mass accuracy hybrid linear ion trap-Orbitrap mass spectrometry

• The HPLC/LTQ-Orbitrap-MS method was developed for screening and confirmation of drugs of abuse simultaneously.
• This method allows for the detection of different drugs of abuse, including amphetamines, cocaine, opiate alkaloids, cannabinoids, hallucinogens and their metabolites.
• This chromatographic optimisation allowed for the separation and detection of 65 drugs of abuse and their metabolites within 20 min.
• Our self-created accurate mass database proved to be feasible for toxicological practice.

A novel analytical toxicology method has been developed for the analysis of drugs of abuse in human urine by using a high resolution and high mass accuracy hybrid linear ion trap-Orbitrap mass spectrometer (LTQ-Orbitrap-MS). This method allows for the detection of different drugs of abuse, including amphetamines, cocaine, opiate alkaloids, cannabinoids, hallucinogens and their metabolites. After solid-phase extraction with Oasis HLB cartridges, spiked urine samples were analysed by HPLC/LTQ-Orbitrap-MS using an electrospray interface in positive ionisation mode, with resolving power of 30,000 full width at half maximum (FWHM). Gradient elution off of a Hypersil Gold PFP column (50 mm × 2.1 mm) allowed to resolve 65 target compounds and 3 internal standards in a total chromatographic run time of 20 min. Validation of this method consisted of confirmation of identity, selectivity, linearity, limit of detection (LOD), lowest limits of quantification (LLOQ), accuracy, precision, extraction recovery and matrix effect. The regression coefficients (r2) for the calibration curves (LLOQ – 100 ng/mL) in the study were ≥0.99. The LODs for 65 validated compounds were better than 5 ng/ml except for 4 compounds. The relative standard deviation (RSD), which was used to estimate repeatability at three concentrations, was always less than 15%. The recovery of extraction and matrix effects were above 50 and 70%, respectively. Mass accuracy was always better than 2 ppm, corresponding to a maximum mass error of 0.8 millimass units (mmu). The accurate masses of characteristic fragments were obtained by collisional experiments for a more reliable identification of the analytes. Automated data analysis and reporting were performed using ToxID software with an exact mass database. This procedure was then successfully applied to analyse drugs of abuse in a real urine sample from subject who was assumed to be drug addict.