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Thin-Layer Chromatography in Pharmaceutical Analysis
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
Elena Dreassi, Giuseppe Ceramelli, Piero Corti
Lavanya and Baggi15 describe a method for the identification and confirmation of cannabinoids present in cannabis, utilizing a process of prechromatographic derivatization that later permits separation of the isomers of the derivatized products of cannabinoids. The method is based on oxidative coupling of cannabinoids with MBTH (3-methyl-2-benzthiazolinone hydrazone MBTH) using acidic eerie ammonium sulphate (CAS) as oxidant. The buffered mixture is deposited on silica gel TLC plates and the chromatography is carried out with benzene–methanol (98:2, v/v). Every cannabinoid presents a visible characteristic coloration; the single compounds may be identified more specifically through application of different wavelengths of UV light. The used compounds are Δ9-tetrahydrocannabinol, cannabinol, cannabidiol, and cannabigerol and the respective values of the Rf are 0.69, 0.83, 0.85, and 0.77. The reproducibility of this method can be compared with other methods based on the postchromatographic derivatization, although they present a higher sensibility. One more advantage of the method described by Lavanya and Baggi consists in the noncancerogenicity of the derivatives and the stability for various days of the chromophores, no interference has been noticed. Without any doubt the derivatization in a prechromatographic phase guarantees a higher reproducibility for quantitative analysis, compared to the induction of the color after the chromatographic development. Thus it can be retained as a good alternative for the detection and identification of cannabinoids in forensic exhibits.
THC-influenced drivers in the new Danish 3-level offense system
Published in Traffic Injury Prevention, 2020
Simon Kjær Hermansen, Tina Ravn Pedersen, Dorte Jensen Christoffersen
Our data show that 73% of the blood samples analyzed for THC in 2017 and 2018 were above the legal limit. This observation is similar to data from the eastern part of Denmark, where 78% of the samples were above the limit in 2015 and 2016 (Simonsen et al. 2018). In addition, a recent Norwegian study comparing results of the Dräger DrugTest 5000 with associated drug findings in blood showed that approximately 84% of drivers found positive for THC were above the Norwegian limit (percentage read from graph; Gjerde et al. 2018). However, this study did not subtract safety margins before evaluating the true positive rate. Furthermore, the Norwegian fixed concentration limit is not completely identical to the Danish fixed concentration limit, thus limiting direct comparison to our results. The Dräger drug test itself is an antibody-based assay designed to supply a preliminary qualitative result that should be followed by confirmatory analysis. Antibody-based assays often struggle with specificity, and a THC-positive drug test could therefore be mediated by the presence of several THC-related compounds not regulated by the law, including cannabidiol, cannabinol, delta8-THC, THC-COOH, THC-OH, and others, creating a risk of false-positive results. Considering the limitations of the current prescreening method in which oral fluid is used as a confirmation matrix instead of blood in combination with forensic analysis in which all doubts are in favor of the accused (reporting minimum values), an approximate 80% true positive rate seems reasonable. With 73% THC-positive cases, our data suggest a slightly lower true positive rate than expected. Some variation could be ascribed to limited access to the drug test in the field. Other factors could be population based; that is, if more samples group around the legislative cutoff, more roadside false positives would be expected due to more impact of misaligned analytical cutoffs and the pharmacokinetic differences in the tested biological matrices (Langel et al. 2014). Additionally, the time elapsed between the field test and blood collection and degradation during storage could affect the outcome (Hartman et al. 2016; Gjerde et al. 2018; Sørensen and Hasselstrøm 2018).