Tetrahydrocannabinol quantification

Figure 16.4. Quantification of A9-tetrahydrocannabinol (9THC) after TFA and 11-nor-9-carboxy-A9-tetrahydrocannabinol (THCCOOH) after PFP in blood using GC-MS/NCI. Drug-free blood was spiked with 9THC (a) and THCCOOH (b) to the concentrations of 0, 5, 10, and 50 or 20ng/mL and with ISs-9THC-D3 and THCCOOH-D3 to 20ng/mL. Monitoring ions were (m/z) 410.3 for 9THC and 572.3 for THCCOOH. The values of validation parameters, expressed in ng/mL, were LOD, 0.25 LOQ, 0.5 limit of linearity, 0.5 to 100 for both analytes [2].

Pharmacological and metabolic studies on cannabinoids (Fig. 1) have suffered from a lack of knowledge of their physico-chemical properties and the insensitivity of assays of A -tetrahydrocannabinol 1, and its metabolites in biological fluids. Unambiguous, sensitive, specific and accurate quantification is required for forensic toxicology and pharmacokinetic studies which can be correlated with the time course of the psychoactive effects (2). 

Improvement of the Mass Fragmentographic Technique for Quantification of Tetrahydrocannabinol in Human Blood Plasma... 

There are a number of reasons why derivatization of samples is necessary. First, the hydroxide and carboxylic moieties may form hydrogen-bonds in the gas phase, thus resulting in poor chromatography. Secondly, the compounds may sorb onto the chromatographic system, resulting in poor chromatography performance, peak shape, and in the case of very low concentrations, non-detection of the analytes. Furthermore, it is known that -tetrahydrocannabinol carboxylic acid thermally decarboxylates at temperatures above 110-120° C, and converts into A -tetrahydrocannabinol. While in some laboratories this is assumed to be quantitative, this may not always be the case. Derivatization will allow determination of both the A -tetrahydrocannabinol and its carboxylic acid. In addition, in the case of very low concentrations of analytes, derivatization will improve the limits of determination and quantification. 

D.H. Fisher, M.I. Broudy and L.M. Fisher, Quantification of 9-carboxy-ll-nor-delta 9-tetrahydrocannabinol in urine using brominated 9-carboxy-ll-nor-delta 9-tetrahydrocannabinol as the internal standard and high-performance liquid chromatography with electrochemical detection, Biomed Chromatogr., 1996, 10, 161-166. 

Improvement of the Mass Fragmento-graphic Techniques for Quantification of Tetrahydrocannabinol in Human Blood Plasma ACS Symp. Ser. 98(Cannabinoid Anal. Physiol. Fluids) 63-79 (1979) CA 91 32564g... 

Chebbah C, Pozo OJ, Deventer K, Van Eenoo P, Delbeke FT (2010) Direct quantification of ll-nor-Delta(9)-tetrahydrocannabinol-9-car-boxyHc acid in urine by liquid chromatography/tandem mass spectrometry in relation to doping control analysis. Rapid Commun Mass Spectrom 24 1133-1141... 

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