title: Hexadeutero-11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid: a superior internal standard for the GC/MS analysis of delta 9-THC acid metabolite in biological specimens.
abstract: GC/MS analysis of biological specimens is believed to be the most forensically accepted method for confirming the presence of abused drugs. 11-Nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (delta 9-THC-COOH) is the major metabolite of delta 9-tetrahydrocannabinol (delta 9-THC) for which testing (including GC/MS) is directed as an indication of marijuana use. The currently available internal standard for delta 9-THC-COOH is d3-delta 9-THC-COOH, which has the deuterium atoms located on the side chain. In addition to the high cost of this compound, it suffers from a limited dynamic range of analysis, especially when the methyl derivative is used. This is because of a contribution to one of the internal standard ions (m/z 316) from a fragmentation of the natural drug which involves loss of the side chain. The new internal standard, d6-11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (d6-delta 9-THC-COOH), avoids these disadvantages. The six deuterium atoms are located on the two methyl groups of Carbon 6 in the dibenzopyran structure. The dynamic range of analysis with the new internal standard was tested between 6.25 to 1,000 ng/mL with a correlation coefficient of 0.998. Analysis of several urine specimens for delta 9-THC metabolite using both d3- and d6-internal standards showed a correlation coefficient of 0.9987.
authors.affiliation: ElSohly Laboratories, Incorporated, Oxford, MS 38655.
authors.forename: M A
authors.initials: MA
authors.lastname: elSohly
authors.forename: T L
authors.initials: TL
authors.lastname: Little
authors.forename: D F
authors.initials: DF
authors.lastname: Stanford
mesh_terms: D013759:Dronabinol / Q000031:analogs & derivatives* / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007202:Indicators and Reagents; D012015:Reference Standards
chemical_list: D007202:Indicators and Reagents; C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol