Despite many studies on cannabinoid pharmacokinetics, the proposals of marker cannabinoids for recent cannabis use, and the introduction of mathematical models estimating the time frame between consumption and blood sampling, it is still challenging for forensic toxicologists to estimate the last time of cannabis exposure. To assess the informative value of determining (minor) cannabinoids in plasma of cannabis users, detection rates of 14 cannabinoids next to Δ⁹‐THC and THC‐COOH (11‐OH‐THC, CBC, CBD, CBN, CBDV, THCV, CBG, CBL, Δ⁸‐THC, THCA, CBDA, CBGA, THCV‐COOH, CBN‐COOH) were determined. Three hundred fifty‐five plasma samples, previously tested positive for cannabinoids (Δ⁹‐THC: approximately 0.4 ng/mL – 125 ng/mL (range), mean: 10.1 ng/mL; THC‐COOH: approximately 3.8 ng/mL – 457 ng/mL (range), mean: 71.6 ng/mL) were analyzed by means of liquid chromatography−tandem mass spectrometry (LC–MS/MS). All analyzed cannabinoids could be detected in plasma samples with varying incidence. 11‐OH‐THC, THCA, CBC, CBN, and CBD were the most frequent detectable cannabinoids (next to Δ⁹‐THC and THC‐COOH). The dependency of cannabinoid detectability on the plasma Δ⁹‐THC concentration and on the probable time of consumption (estimated by a model of Huestis and coworkers) was examined. Detection incidences (eg, 11‐OH‐THC, CBC) often increased with increasing Δ⁹‐THC concentration but not for all cannabinoids (eg, CBD, THCA). The presented data for minor cannabinoid findings in plasma can be helpful for a comprehensive interpretation of cannabinoid findings in plasma samples of cannabis users.

In forensic toxicology, amphetamine intoxications represent one of the most common case groups and present difficult questions for toxicologists. Estimating the time of consumption and the current influence of the stimulant is particularly difficult when only total amphetamine concentrations are considered. Stereoselective analysis and the consideration of metabolites can provide valuable information to facilitate interpretation. An enantioselective liquid chromatography−tandem mass spectrometry (LC-MS/MS) method for detection of amphetamine, norephedrine and 4-hydroxyamphetamine was developed. Validation showed satisfactory selectivity, sensitivity, linearity (0.5–250 ng/mL), precision and accuracy for all enantiomers. The method was applied to a collective of 425 forensic serum samples and 30 serum samples from psychiatric inpatients stating their last time of amphetamine consumption. Norephedrine and 4-hydroxyamphetamine were detected more frequently at higher amphetamine concentrations and at lower amphetamine (R)/(S) concentration ratios, possibly indicating recent consumption. Mean (R)/(S) ratio of amphetamine was 1.14, whereas higher ratios (mean 1.36) were found for amphetamine concentrations below 100 ng/mL. The (R)/(S) ratios of psychiatric inpatients significantly correlated with the reported time intervals to last consumption. The use of amphetamine (R)/(S) ratios and the simultaneous detection of metabolites are promising factors that can facilitate estimation of consumption time and current impairment.