Towards an efficient method for the extraction and analysis of cannabinoids in wastewater

Owing to the risks and dangers of xenobiotic cannabinoids (phyto and synthetic), studies are required to evaluate community consumption. The analysis of excreted cannabinoids in wastewater can provide information about community consumption for a defined catchment area. The recovery of cannabinoids from complex wastewater matrices is difficult due to the hydrophobic properties of these compounds. In this study, a liquid chromatography tandem mass spectrometry (LC-MS/MS) method was optimised for the recovery of 30 cannabinoids from wastewater, including the cannabis urinary biomarker 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH), cannabidiol (CBD), and a variety of different generational synthetic cannabinoids and metabolites. Method validation assessed criteria including linearity, selectivity, recovery, ion-suppression, filtration losses and matrix effect. Two sample preparation approaches-liquid-liquid extraction (LLE) and solid phase extraction (SPE)-were compared, with comparable limits of quantification between 0.001 and 0.5 µg L^-1 in wastewater. Filtration was found to reduce the recovery for many of the investigated cannabinoids, where up to 97% of analyte was lost. The method was applied to 15 different catchment areas across Australia to gauge the community use of the cannabinoids in this study. The cannabis biomarker THC-COOH was quantified at all locations, and cannabidiol was measured at eight catchment areas. Three synthetic cannabinoids were detected at the limit of detection: 5-fluoro APINACA, JWH-073 (4-hydroxypentyl), and MDMB-CHMICA.