TITLE:
The Detection of THCA Using 2-Dimensional Gas Chromatography-Tandem Mass Spectrometry in Human Fingernail Clippings: Method Validation and Comparison with Head Hair
AUTHORS:
Joseph Jones, Mary Jones, Charles Plate, Douglas Lewis
KEYWORDS:
11-Nor-9-Carboxy-Δ9-Tetrahydrocannabinol; THCA; Carboxy-THC; Hair; Fingernail; 2D-GC-MS/MS; 2-Dimensional Gas Chromatography Tandem Mass Spectrometry
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.4 No.10B,
October
9,
2013
ABSTRACT:
Marijuana use as well as abuse is a significant public health
and public safety concern in the United States and using hair to identify
marijuana users and abusers has been gaining acceptance in a number of venues
including workplace, court ordered, and substance abuse treatment monitoring.
After the presentation of a fully validated 2-dimensional gas
chromatography-tandem mass spectrometry method for the detection of
11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCA), the chief metabolite of the main
psychoactive compound in marijuana, Δ9-tetrahydrocannabinol (THC), we evaluated the usefulness of
fingernail clippings as an alternative specimen type to hair by the analysis of
a set of 60 matched pairs of head hair and fingernail clippings. The limit of
detection was 10 fg/mg, the limit of quantitation was 20 fg/mg, and the assay
was linear from 20 fg/mg to 500 fg/mg. The intra- and inter-assay imprecision
and bias studies at 4 different concentrations (50, 100, 500, and 1000 fg/mg)
were acceptable where all % Target observations were within 16% of their
expected concentrations and all %CV calculations were less than 13.5%. THCA was
detectable in more fingernail specimens (53.3%) than hair specimens (46.7%) and
the mean concentrations in nails were on average 4.9 times higher than in hair
(1813 fg/mg and 364 fg/mg, respectively). The THCA concentrations in hair and
nail were strongly associated (r = 0.974, P