Determination of a synthetic cannabinoid RCS-4 with its metabolite from serum sample by LC-MS/MS

Synthetic cannabinoids are psychoactive substances known by names such as 'Spice', 'K2', 'Bonzai', 'Jamaica', whose production and consumption have increased since 2004. While the main purpose of the production of synthetic cannabinoids is to investigate the endocannabinoid system, the fact that they have almost the same effects as cannabis makes them a current and lucrative source for the drug market. Since synthetic cannabinoids act as full agonists to cannabinoid receptors, they act faster than cannabis, leading to faster addiction and more damage. This is why the number of sudden deaths associated with synthetic cannabinoid use is increasing. Synthetic cannabinoids, which are often sprayed on natural plants or plant mixtures to mimic the effects of cannabis and sold as "herbal smoking mixtures" or "herbal incense", are very easy to access today and pose a serious threat to public health. However, the fact that their chemical structure can change very easily causes both a large variety of substances and difficulty in detecting them with existing analyzes. Therefore, identification, detection and validation studies on these substances are important. This study was carried out to determine RCS-4, a synthetic cannabinoid, and its main metabolite RCS-4-N(5-carboxypentyl) from serum by enzymatic hydrolysis method using LC-MS/MS ORBITRAP system and to validate the method. In selectivity studies, the selectivity of RCS-4 and its metabolite RCS-4-N(5-carboxypentyl) in serum was investigated and no peak was found in blind serum samples. The linear range was 0-100 ng/mL and the correlation coefficient for RCS-4 and RCS-4-N(5-Carboxypentyl) was higher than 0.990. The limit of detection (LOD) for RCS-4 and RCS-4-N(5-Carboxypentyl) in serum sample is 5.679 - 6.623 ng/mL and the limit of quantification (LOQ) is 18,930 - 22,076, respectively. For the accuracy study, repeatability and reproducibility studies were performed and precision and recovery were evaluated based on these results. Accordingly, %RSD values were found to be 0.09 - 0.07 - 0.1 for RCS-4 at concentrations of 10, 50 and 100 ppb and 0.15 - 0.11 - 0.1 for RCS-4-N(5-Carboxypentyl), respectively. The recovery values for RCS-4 were in the range 97.54% - 104.21% and for RCS-4-N(5-Carboxypentyl) in the range 88.87% - 118.93%. All of the validation parameters studied are within the acceptance ranges of the international guidelines for the validation of toxicological analyses. Thus, the validity of the method for the detection and determination of RCS-4 and RCS-4-N(5-Carboxypentyl) in serum samples has been proven. This method will make an important contribution to the clarification of forensic cases.