The confirmation of δ9-tetrahydrocannabinol (THC) in oral fluid (OF) is an important issue for assessing Driving Under the Influence of Drugs (DUID). The aim of this research was to develop a highly sensitive method with minimal sample pre-treatment suitable for the analysis of small OF volumes (100. μL) for the confirmation of cannabinoids in DUID cases. Two methods were compared for the confirmation of THC in residual OF samples, obtained from a preliminary on-site screening with commercial devices. An ultra high performance LC-MS (UHPLC-MS/MS) method and an SPME-GC/MS method were hence developed. 100. μL of the residual mixture OF/preservative buffer or neat OF was simply added to 10. μL of THC-D3 (1. μg/mL) and submitted to the two different analyses: A - direct injection of 10. μL in UHPLC-MS/MS in positive electrospray ionisation (ESI) mode and B - sampling for 30. min with SPME (100. μm polydimethylsiloxane or PDMS fibre) and direct injection by desorption of the fibre in the GC injection port. The lowest limit of detection (LLOD) of THC was 2. ng/mL in UHPLC-MS/MS and 0.5. ng/mL in SPME-GC/MS. In addition, cannabidiol (CBD) and cannabinol (CBN) could be detected in GC/MS equipment at 2. ng/mL, whilst in UHPLC-MS/MS the LLOD was 20. ng/mL. Both methods were applied to 70 samples coming from roadside tests. By SPME-GC/MS analysis, THC was confirmed in 42 samples, whilst CBD was detected in 21 of them, along with CBN in 14 samples. THC concentrations ranged from traces below the lowest limit of quantification or LLOQ (2. ng/mL) up to 690. ng/mL.
- Liquid chromatography tandem mass spectrometry
- Oral fluid
- Solid phase microextraction