Studies on confirmation of cannabis use. I. Determination of the cannabinoid contents in marijuana cigarette, tar, and ash using high performance liquid chromatography with electrochemical detection.

A high performance liquid chromatography-electrochemical detection (HPLC-ECD) method was used for the highly sensitive and simultaneous determination of free cannabinoids and cannabinoic acids without derivatization. The HPLC-ECD method was linear from 5 to 500 ng/injection for all cannabinoids (THC, CBN, CBD, CBCh, THCA, CBDA, and CBChA). The detection limits of this method were 0.5 to 0.9 ng/injection for free cannabinoids and 1.2 to 2.5 ng/injection for cannabinoic acids at signal noise ratio of greater than 4. Cannabinoic contents in marijuana cigarettes and in tar and ash obtained by using an automatic smoking machine were measured by this method. Consequently, 62% of the sum of THC and THCA in the marijuana cigarette was converted to tar and 2.0% of that was left in the ash.