Dried blood spot testing: an innovative approach to overcome cannabinoid instability in blood

Cannabis is the most widely used illicit drug around the world and among the drugs of abuse (DoA) most frequently involved in street accidents. Therefore, it is important to strictly monitor Cannabis abuse. Until now, the most reliable biological matrix for this purpose is represented by blood (whole blood/plasma), which can provide useful information about drug consumption. However, its sampling and storage require complicated and time consuming precautions, such as centrifugation and refrigeration or freezing, in order to preserve analyte stability. To overcome these disadvantages the use of Dried Blood Spots (DBSs) represents a valid alternative to the “classical” blood sampling. This innovative biological matrix reproduces the composition of whole blood but its pre-treatment procedure is faster and more feasible. DBSs can be stored for months at room temperature without any appreciable sample degradation, since most enzymatic and non-enzymatic reactions are stopped by the loss of water. The aim of this work is the specific evaluation of cannabinoid stability in DBSs, namely of Δ9 tetrahydrocannabinol (THC), the most important psychoactive cannabinoid, and of its two main metabolites 11-hydroxy-Δ9-tetrahydrocannabinol (THC-OH) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH). For this study, blank spiked DBSs were stored at room temperature for up to 3 months after sampling and then analysed by ESI-LC-MS/MS. The sample pre-treatment, based on solvent extraction, provides good extraction yields and selectivity. Preliminary results are very satisfactory, since only minimal differences were observed between the samples analysed immediately after spotting and those analysed after storage. Further assays are in progress to confirm these results and to assess cannabinoid stability in DBSs over longer periods of time.