Abstract
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 >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.

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