Muhammad Aamir, Ayesha Hafeez, Aamir Ijaz, Saleem Ahmed Khan, Nayyar Chaudhry, Nisar Ahmed.
Development and validation of a liquid chromatography - tandem mass spectrometry method for cannabis detection in hair of chronic cannabis users under surveillance.
Pak J Pathol Jan ;27(2):61-9.

Objective: To develop and validate a method on liquid chromatography-mass spectrometry for simultaneous detection of two cannabinoid metabolites in hair and to subsequently apply this method for surveillance of chronic cannabis users. Study design: Cross sectional (validation) study. Place & duration of study: Departments of Forensic Medical Sciences Laboratory, Forensic Toxicology Section, Armed Forces Institute of Pathology, Rawalpindi Pakistan. Materials and Methods: Hair samples from about 60 chronic cannabis addicts were collected. After washing, decontamination and alkaline hydrolysis, the samples were extracted with n-hexane: ethyl acetate, centrifuged and reconstituted with methanol. Separation of compounds was achieved with Agilent Poroshell 120 EC-C18 column (2.1 x7.5mm.7 micron). For detection and quantification, a 6460 Tripple quadrapole LCMS having an ESI source with jet steam technology along with software Mass hunter was used. Results: Intra- and inter-assay bias was below 8% and relative standard deviation below 10% for both metabolites. The limit of quantification for both THC and THC-COOH were validated at 100pg/mg. The method was validated in terms of linearity, carry over, selectivity (no endogenous or exogenous interferences); precision and accuracy; limits of detection and quantification and matrix effects (ion suppression and enhancement). It was then applied to testing of real hair samples from 55 chronic cannabis users. Conclusion: The presented method allows simultaneous quantitation of THC and THC- COOH in hair of chronic cannabis users under surveillance, utilizing LCMS. Analysis for drugs of abuse in hair however remains a formidable analytical challenge and laboratories need to develop methodologies which efficiently release the drug from its solid matrix and are free from interferences to achieve the desired sensitivity.Keywords: Liquid chromatography-mass spectrometry, Cannabinoid, Validation.

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