Quantification of ∆9-tetrahydrocannabinol, 11-OH-THC, THC-COOH, hexahydrocannabinol, and cannabidiol in human plasma and blood by liquid chromatography-tandem mass spectrometry.

Ongoing legalization of cannabis for recreational use contributes to increasing numbers not only of incidents of driving under the influence, but within all forensic fields. In addition, newly emerging cannabinoids such as hexahydrocannabinol (HHC) and the increasing use of cannabidiol (CBD) products have to be addressed. The aims of this study were first to extend laboratory analysis capacity for the "established" cannabinoid ∆9-tetrahydrocannabinol (THC) and its metabolites 11-OH-THC and THC-COOH in human plasma/blood, and second to develop analytical procedures concerning HHC and CBD. An LC-MS-MS method based on the available (low-end) instrumentation was used. Samples (250 µl) were prepared by protein precipitation and solid-phase extraction. Chromatographic separation was achieved on a reversed-phase C18 column within 15 min. Detection was performed on a 3200 QTRAP instrument (Sciex) in positive multiple reaction monitoring (MRM) mode. Matrix-matched six-point calibrations were generated applying deuterated internal standards for all analytes except HHC. The method was fully validated according to GTFCh guidelines. Linear ranges were 0.5-25 µg/l for THC, 11-OH-THC, HHC and CBD, and 2.0-100 µg/l for THC-COOH, respectively. Limits of detection and limits of quantification were 0.5 and 1.0 µg/l (THC, 11-OH-THC, HHC, CBD), and 2.0 and 4.0 µg/l (THC-COOH). Applicability of plasma calibrations to blood samples was demonstrated. Acceptance criteria for intra- and inter-day accuracy, precision, extraction efficiency, and matrix effects were met. No interfering signals were detected for 80 exogenous compounds. The presented method is sensitive, specific, easy to handle, and does not require high-end equipment. Since its implementation and accreditation according to ISO 17025, the method has proven to be fit for purpose not only in driving under the influence of drug cases but also within postmortem samples. Furthermore, the design of the method allows for an uncomplicated extension to further cannabinoids if required.