Quantitative determination of 11-nor-9-carboxy-tetrahydrocannabinol in hair by column switching LC–ESI-MS3

Hair analysis has been regarded as an alternative method to urine analysis in forensic and criminal cases. Cannabis (marijuana) is one of the most widely used drugs in the world and it has been controlled in South Korea since 1976. Identification of 11-nor-9-carboxy-tetrahydrocannabinol (THCCOOH) in hair can be an important proof of cannabis use because it can exclude the possibility of passive cannabis smoke exposure. In this study, we described a quantitative method of THCCOOH in hair using simple liquid–liquid extraction (LLE), selective column switching liquid chromatography with electrospray ionization (ESI)-MS3. For the column switching system three columns (precolumn, trap column and analytical column) were used. Valve switch from the precolumn to the trap column was set from 3.0 to 4.0 min because THCCOOH appeared around 3.5 min with this precolumn. After 4.0 min the valve was switched to the original position and the analytes in the trap column were eluted onto the analytical column. Resolution occurred in this column and eluted into the ESI-MS3 system. The internal standard was THCCOOH-d3. We used ESI-negative-MS3 transition of ions at m/z 343 to 299 to 245 (343/299/245) and m/z 346 to 302 to 248 (346/302/248) for quantification of THCCOOH and THCCOOH-d3, respectively. The validation results of selectivity, matrix effect, recovery, linearity, precision and accuracy, and processed sample stability were satisfactory. The limit of detection (LOD) was 0.05 pg/mg and the limit of quantification (LOQ) was 0.10 pg/mg. The range of concentration of THCCOOH from 98 authentic human hair was 0.13–15.75 pg/mg. This method was successfully applied in the analysis of authentic human hair samples.