Voltammetric Determination of Synthetic Cannabinoids in Confiscated Street Samples and Artificial Saliva

Marina Dronova, The Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel
Evgeni Smolianitski, The Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel
Bismuth Cohen, Department of Identification and Forensic Science, Israeli Police, Jerusalem, Israel
Ovadia Lev, The Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel

The recent appearance of synthetic cannabinoids in herbal products (“Spice”), easily available over the Internet, has brought to the attention of the international community the need for analytical methodologies that can provide confirmatory analysis together with on-the-spot analytical screening tools that could be used to determine whether a substance or sample matrix contains such «legal highs».

In this work the electrochemical sensing of one of the largest groups of psychoactive substances – synthetic cannabinoids, is explored for the first time. The investigation was performed for six indole and five indazole based cannabinoids that are currently found on the Israeli market.

Direct electrochemical oxidation of synthetic cannabinoids was found to be possible, giving useful voltammetric electroanalytical signatures in non-aqueous and aqueous buffer solutions. This investigation was performed using cyclic and differential pulse voltammetry, at a range of commercially available electrodes (Pt, glassy carbon and boron doped diamond). It was found that indole and indazole based synthetic cannabinoids produce a voltammetric response which can be used for their determination. Best detection and quantification limits were achieved using anodically pretreated bdd electrode, showing that synthetic cannabinoids can be detected in artificial saliva over the nanomolar range. To gain insight into the electro-oxidation mechanisms of this class of molecules, controlled - potential electrolysis in combination with ESI–QTOF–MS and GC–SMB–EI–QQQ–MS analysis of oxidation products was done. On the basis of these data, electro-oxidation mechanism was proposed and discussed. The proposed electroanalytical protocol for the determination of cannabinoids in confiscated street samples and artificial saliva has been tested and independently verified by GC-MS and LC-MS, demonstrating excellent agreement between the different tools. Thus, there is a potential forensic application of the electrochemical method to be used «on-site» for the screening, or even preliminary quantification, of common synthetic cannabinoids found within real seized street samples or in body fluids.