A study on the concentrations of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in hair root and whole hair

In this study, we investigated the patterns of cannabis users (n = 412) according to their sex, age, and the results of urinalysis and hair analysis, and classified the concentrations of THCCOOH in hair into three categories to examine the levels of cannabis use. We also compared the concentrations of THCCOOH in hair root, hair without the hair root and whole hair and examined the relationship among them according to the results of urinalysis.The hair samples were washed, digested with 1 ml of 1 M NaOH at 85 °C for 30 min and extracted with 2 ml of n-hexane:ethyl acetate (9:1) two times after adding 1 ml of 0.1 N sodium acetate buffer (pH 4.5) and 200 μl of acetic acid. The final mixture was derivatized with 50 μl of PFPA and 25 μl of PFPOH for 30 min at 70 °C. The solution was evaporated, and the residue was reconstituted in 40 μl of ethyl acetate and transferred to an autosampler vial. One microlitre was injected into the GC/MS/MS-NCI system.The concentrations of THCCOOH ranged from 0.06 to 33.44 pg/mg (mean 2.96; median 1.32) in hair from cannabis users who had positive urine results and ranged from 0.05 to 7.24 pg/mg (mean 1.35; median 0.37) in hair from cannabis users who had negative urine results. The average concentration of THCCOOH in hair from cannabis users who had positive urine results was higher than that from cannabis users who had negative urine results. Male cannabis users in their forties were predominant. We classified the concentrations of THCCOOH in hair into three groups (low, medium and high), and could use the grouping of THCCOOH in hair as a guide for determining the level of use. The low, medium and high concentration ranges for THCCOOH in hair were 0.05–0.24, 0.25–2.60 and 2.63–33.44 pg/mg, respectively. We also investigated 28 hair samples with the root. The highest concentrations of THCCOOH were seen in the hair root from 18 out of the 28 hair samples. The average concentrations of THCCOOH in hair root, hair without hair root and whole hair from cannabis users who had positive urine results were higher than those who had negative urine results.