Analysis of (–)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol and (–)-11-nor-9-carboxy-Δ8-tetrahydrocannabinol in hair from a school-age population

A sensitive liquid chromatography-tandem mass spectrometry method for the detection of (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol and (-)-11-nor-9-carboxy-Δ8-tetrahydrocannabinol in hair with a cutoff of 1 pg/10 mg of hair and a limit of quantitation of 0.2 pg/10 mg of hair for both analytes was developed and is herein described. A subset of samples collected from a school-age population between December 2022 and February 2023 was analyzed using this method after having screened presumptive positive by enzyme immunoassay out of a total pool of approximately 5300 samples. Of these presumptive positive samples, 66% showed the presence of one or both analytes at a concentration ≥1 pg/10 mg of hair. Of the 213 positive samples, 57% contained more (-)-11-nor-9-carboxy-Δ8-tetrahydrocannabinol than (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol and 6% contained more than 50-fold higher Δ8 isomer than Δ9 isomer. Of the 197 samples that were reportable for (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol ≥1 pg/10 mg cutoff, 53% of them contained more (-)-11-nor-9-carboxy-Δ8-tetrahydrocannabinol than (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol. Of the 197 samples that were reportable for (-)-11-nor-9-carboxy-Δ8-tetrahydrocannabinol ≥1 pg/10 mg cutoff, 15.7% exceeded the upper limit of linearity of the method (200 pg/10 mg). These results suggest a high level of (-)-Δ8-tetrahydrocannabinol usage in this population relative to (-)-Δ9-tetrahydrocannabinol usage. They further suggest the possibility that (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol reported for some of these samples may only have been present due to (-)-Δ9-tetrahydrocannabinol contamination of (-)-Δ8-tetrahydrocannabinol products being consumed in large quantities. Thus, reported results for (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol alone may give a false picture of the extent of the cannabis product being consumed by a test subject.