Quantitative analysis of Δ9-THC-COOH in Human Urine by the Liquid-Liquid Extraction technique and Gas Chromatography-Mass Spectrometry: Adaptation, Optimization and Validation

Abstract

The main active compound of Cannabis sativa is Δ9-tetrahydrocannabinol, which is quickly transformed into 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (Δ9-THC-COOH) in the human body. This research aimed to validate an efficient, fast and low-cost technique for Δ9-THC-COOH analysis in urine with adaptations of existing analytical methods. The validation process was carried out in accordance with guidelines published by ANVISA and with international guidelines. The analyte was extracted by liquid-liquid extraction and identified/quantified by gas chromatography coupled to mass spectrometry. Linear curves ranges were from 5 to 300 ng mL-1 (r = 0.9993; y= 0.0269x – 0.0364). Intra and inter-day precision varied from 3.38 to 9.04% and accuracy was between 83 to 112.9%. The Δ9-THC-COOH remained stable after 15-30 days of storage at -20 °C (long-term test), after 5 freeze-thaw cycles and post-processing for up to 72 hours. The method is fast, low-cost, with detection limits and quantification below the cut-off (15 ng mL-1), which makes it useful and efficient for routine use at toxicology laboratories, for drug addiction and doping control, for forensic purposes and also for controlling the use of drugs of abuse by vehicle drivers.

Simple Method for the Determination of THC and THC-COOH in Human Postmortem Blood Samples by Gas Chromatography—Mass Spectrometry

“…Liquid-liquid extraction is quick, efficient, and often more favourable for postmortem blood due to the nature of the sample matrix [20,34]. Blood plasma is generally considered the most useful sample for drug identification in quantitative analyses; likewise, given that psychoactive substances that are tested often leave the blood rapidly, this sample is most useful for the purpose of identifying the recent use of drugs.…”