Numerous publications outlining the quantitative determination and semi-quantitative screening for both parent and metabolites of the natural plant derived cannabinoids have been reviewed due to the widespread use and abuse of cannabinoid containing substances. Synthetic cannabinoids have become fairly easily accessible as recreational drugs during recent times and are continually being structurally changed to increase the hallucinogenic effects and to avoid being specifically listed as illegal compounds.
The most common sample type to be used for identification and quantification of cannabinoids in humans is urine, which is currently tested using immunology-based methods. These methods require specific antibodies for each possible new synthetic cannabinoid in addition to the many different possible metabolites that form after oral or inhaled administration. These antibody-based assays are in general expensive, show cross-reactivity and are prone to high analyst-based variations. Advanced analytical techniques such as ultra-pressure liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) can be a more cost effective method and can be applied routinely for qualitative and quantitative analysis of the ever-changing combinations of cannabinoid compounds being abused.
The need in the laboratory for testing for each of the known plant derived cannabinoids as well as for several synthetic cannabinoids has in recent times increased. Herbal products sold legally in some retail shops, tobacco shops, bottle stores and via the internet, have been shown to contain both natural and synthetic cannabinoid compounds. This study developed and optimised a rapid ultra-performance liquid chromatographic tandem mass spectrometry method to quantitatively determine low concentrations of the natural cannabinoids and three of the most commonly used synthetic cannabinoid compounds, namely JWH-018; JWH-073 and HU-210 and their respective metabolites in both human plasma and urine. Chromatographic separation was achieved on an Acuity UPLC Cortex C18 Phenyl 100 X 2.1 mm 1.6 μm column. Urine samples were initially enzymatically hydrolysed to release the glucuronide and sulphate groups that are commonly conjugated to the metabolites, using standard enzymatic hydrolysis procedures, then analysed directly following dilution with 1% formic acid in methanol. Plasma samples were initially extracted using solid phase extraction prior to analysis. Both urine and plasma analysis used stable-isotope labelled analogues of the natural and synthetic cannabinoid analytes as internal standards. Analyses of the samples were performed by tandem mass spectrometry in positive electrospray ionization mode with selected reaction monitoring. The total analytical run time was 14 minutes. The linear dynamic range was between 1-100 μg/L with a lower limit of detection in urine for JWH-073-4-hydroxy-butyl of 1.31 μg/L; 11-hydroxy THC was 8.66 μg/L; 11-Nor-Delta-Carboxy THC was 2.66 μg/L; JWH-210-4-hydroxy-pentyl was 1.18 μg/L; JWH-210-5-hydroxy-pentyl was 2.53 μg/L respectively. The elimination half-life of the cannabinoid metabolites in plasma is very short due to the effective renal excretion of these metabolites, and therefore only the precursor cannabinoids could be identified in plasma using the developed methods. Detection limits for the natural cannabinoids in plasma were: Cannabinol was 6.78 μg/L; Cannabidiol was 5.56 μg/L; Delta 9 THC was 2.40 μg/L; while for the synthetic cannabinoids: JWH-073 was 0.15 μg/L; JWH-018 was 8.71 μg/L and HU-210 was 1.03 μg/L.
Intra-run imprecision at concentration levels of 10 and 50 μg/L for JWH-073-4-hydroxy butyl was 1.32 μg/L and 1.57 μg/L respectively; 11-Hydroxy-THC was 3.02 μg/L and 4.02 μg/L respectively; 11-Nor 9 carboxy THC was 2.17 μg/L and 4.55 μg/L respectively; JWH-210-4-hydroxy-pentyl was 2.21 μg/L and 1.93 μg/L respectively; HU-210-5-hydroxy-pentyl was 2.0 μg/L and 2.65 μg/L respectively. The intra-run imprecisions for the non-metabolised compounds at the same concentration levels were slightly higher with: Cannabinol at 2.43 μg/L and 8.72 μg/L respectively; Cannabidiol at 1.54 μg/L and 3.79 μg/L respectively; Delta 9 THC at 1.96 μg/L and 3.03 μg/L respectively; JWH-073 at 2.25 μg/L and 3.57 μg/L; JWH-018 at 2.64 μg/L and 3.83 μg/L respectively and HU-210 at 5.49 μg/L and 5.64 μg/L respectively
In conclusion the method performance compares to methods reported in literature where different classes of cannabinoids have been analysed. In addition, improvement in turn-around time and reduction in analysis cost could be implemented. The newly developed method, used in an analytical laboratory will aid to confirm whether the patients have indeed been administered natural or synthetic cannabinoids. This can help a referring General Practitioner to make quicker decisions to minimize long-term effects of the cannabinoids. In practice, analytical laboratory performance is dependent on implementation of Good Laboratory Practise (GLP) that includes following well documented standard operating procedures of validated analytical methods. With pharmacokinetic studies a validated protocol must be followed for a study to be accepted.