Can synthetic cannabinoids be reliably screened with electrochemistry? An assessment of the ability to screen for synthetic cannabinoids STS-135 and BB-22 within a single sample matrix

Synthetic cannabinoids (SC) are one of the most prevalent classes of novel psychoactive substances (NPS) which have emerged onto the drug market in recent years. The incompatibility of traditional colorimetric screening methodologies with these new compounds has left a significant gap in the forensic tool kit available to tackle the importation and distribution of these substances. Electrochemical techniques have proven success for screening of such substances, but no consideration to date has been given to the impact upon the electrochemical behaviour when multiple SC are present within a single matrix. To this avail we investigate the impact of combining two SC, STS-135 and BB-22 into a single matrix to simulate a street sample composition. Interrogation of the combine two SC revealed a significant change to their electrochemical behaviour. Combination of the two indole species was revealed to undergo electrochemically induced indole polymerisation, forming a secondary species in the form of an indole dimer. Thus, removing an electrochemical centre form the formerly electroactive pyrrole group. This previously unseen mechanism revealed the inability of electrochemical screening techniques to accurately determine the number of species or indeed concentrations present given the change in structure and consequently the electrochemical behaviour observed. As such, further assessment of the feasibility of electrochemical techniques for the screening of SC is required with consideration now given to electrochemically induced competing side reactions which may occur between species within the matrix.