Zamengo Luca, Bettin Chiara, Badocco Denis, Di Marco Valerio, Miolo Giorgia, Frison Giampietro
Laboratory of Environmental Hygiene and Forensic Toxicology, DMPO Department, AULSS 3 Serenissima, Venice, Italy.
Laboratory of Environmental Hygiene and Forensic Toxicology, DMPO Department, AULSS 3 Serenissima, Venice, Italy.
Forensic Sci Int. 2019 May;298:131-137. doi: 10.1016/j.forsciint.2019.02.058. Epub 2019 Mar 8.
The aim of this study was to investigate the role of time and different real-life storage conditions on the composition of different varieties of cannabis products (hashish and marijuana). Six high-potency cannabis products constituted by herbal and resin materials containing different initial concentrations of delta 9-Tetrahydrocannabinol (THC) were employed for this study. Four representative samples were collected from each study material and were maintained for a prolonged time (four years) under different controlled storage conditions: (A) light (24 h) and room temperature (22°C); (B) darkness (24 h) and room temperature; (C) darkness and refrigeration (4 °C); (D) darkness and freezing (-20 °C). The concentration of the three main cannabinoids, i.e. THC, Cannabinol (CBN, produced from the degradation of THC), and Cannabidiol (CBD), were measured by GC-FID around every 100 days along the four-year study. Significant changes in the THC (degradation) and CBN (formation) content were detected under storage conditions A and B, and almost 100% of THC was degraded after four years. A mono-exponential function was able to well fit both THC degradation and CBN formation, suggesting that these processes occur with a first order kinetics. Data treatment indicated that the storage temperature and light exposure had two different effects on the conversion of THC to CBN: temperature changed only the speed, light changed both the speed and the stoichiometry of this conversion. Models were proposed which allow to predict the storage time, if unknown, and the initial content of THC (i.e. the concentration of THC at the starting storage time), from the measurement of THC and CBN content at any time under storage condition A. Values predicted are more uncertain at larger storage times and have an accuracy of around 5-10%. These models were also tested on data reported in the literature, and can represent a starting point for further improvements. Prediction models may be helpful for forensic purposes, if the initial concentration of THC or the approximate age of a degraded material need to be estimated, or to plan the storage of delicate samples which need to be re-examined over time.
本研究的目的是调查时间和不同实际储存条件对不同品种大麻产品（哈希什和大麻）成分的影响。本研究采用了六种由含有不同初始浓度δ9-四氢大麻酚（THC）的草药和树脂材料构成的高效能大麻产品。从每种研究材料中采集四个代表性样本，并在不同的受控储存条件下保存较长时间（四年）：（A）光照（24小时）和室温（22°C）；（B）黑暗（24小时）和室温；（C）黑暗和冷藏（4°C）；（D）黑暗和冷冻（-20°C）。在为期四年的研究中，每隔约100天通过气相色谱-火焰离子化检测法（GC-FID）测量三种主要大麻素的浓度，即THC、大麻酚（CBN，由THC降解产生）和大麻二酚（CBD）。在储存条件A和B下，检测到THC（降解）和CBN（形成）含量有显著变化，四年后几乎100%的THC被降解。单指数函数能够很好地拟合THC降解和CBN形成，表明这些过程以一级动力学发生。数据处理表明，储存温度和光照对THC向CBN的转化有两种不同的影响：温度仅改变速度，光照既改变速度又改变这种转化的化学计量。提出了一些模型，这些模型可以根据在储存条件A下任何时间测量的THC和CBN含量来预测未知的储存时间以及THC的初始含量（即开始储存时THC的浓度）。在较长的储存时间下预测值的不确定性更大，准确度约为5-10%。这些模型也在文献报道的数据上进行了测试，可作为进一步改进的起点。如果需要估计THC的初始浓度或降解材料的大致年龄，或者为计划对需要随时间重新检查的精密样本进行储存，预测模型可能有助于法医鉴定。
