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Ultra-Sensitive Measurements of 11-Nor‑Δ9‑Tetrahydrocannabinol-9-Carboxylic Acid in Oral Fluid by Microflow Liquid Chromatography–Tandem Mass Spectrometry Using a Benchtop Quadrupole/Orbitrap Mass Spectrometer
journal contribution
posted on 2012-09-18, 00:00 authored by Xiang He, Marta Kozak, Subodh NimkarOral fluid has been gaining more acceptance as the alternative
matrix for forensic toxicology. Currently, Δ9-tetrahydrocannabinol
(THC) is used as the primary target for detecting cannabis use in
oral fluid. Meanwhile, THC carboxylic acid (THCA) in oral fluid is
reported as a more reliable marker for cannabis abuse as its presence
does not come from passive exposure. An analytical method for simultaneous
quantitation of THC and THCA will be efficient for toxicology laboratories.
THCA quantitation is challenging due to its very low concentration
in oral fluid. Recently reported liquid chromatography–tandem
mass spectrometry (LC–MS/MS)-based methods achieved sufficient
sensitivity but involved complex sample preparation procedures. We
aimed to develop a sensitive LC–MS/MS method for simultaneous
quantitation of THC and THCA in oral fluid with low-flow liquid chromatography
and a Q Exactive mass spectrometer, using offline sample preparation
of oral fluid followed by microflow LC with online sample cleanup.
The total runtime of the method was 12.5 min. The method had a lower
limit of quantitation of 7.5 pg/mL and was linear from 7.5 to 300
pg/mL for THCA. The intra- and interbatch precision of the method
ranged from 3.3% to 9.3% for THC and THCA.