Fully Automated SPE/GC/MS-Analysis of Δ9-Tetrahydrocannabinol (THC) and its Metabolites in Serum Samples

This note presents a fully automated analysis system for the determination of Δ9-tetrahydrocannabinol (THC) and its metabolites in blood serum. Automation is based on the GERSTEL MultiPurpose Sampler (MPS) equipped for solid phase extraction (GERSTEL SPE) and a module for automated eluate evaporation (GERSTEL MultiPosition Evaporation Station, mVAP).

A validated, semi-automated analysis method used for routine analysis was transferred and automated using the described system. Improvements were realized such as a reduction of the sam - ple volume used from 1 to 0.5 mL serum and the use of smaller 1 mL for mat SPE cartridges. The analysis method has been validated according to GTFCh guidelines (Society of Toxicological and Forensic Chemistry). Limits of quantification below 1 ng/mL for THC and THC-OH, extraction efficiencies between 70 and 93 % and relative standard deviations between 3.3 and 10 % were achieved. The SPE system performs sample preparation in parallel with the chromatographic run, enabling the GC/MS-system to op- erate at maximum productivity and full capacity.