Indirect detection of substituted phenols and cannabis based on the electrochemical adaptation of the Gibbs reaction.

The voltammetric behaviour of 2,6-dichloro-p-aminophenol (PAP) in aqueous solution at an edge plane pyrolytic graphite electrode was explored and its sensitivity to additions of substituted phenols examined. Proof of concept is shown for the electrochemical adaptation of the Gibbs reaction, where reaction of the oxidised form of PAP with substituted phenols provides an indirect methodology for the analytical detection of these compounds. This indirect protocol provides an attractive alterative to the direct electrochemical oxidation of phenolic compounds, since the latter is plagued by electrode passivation, leading to low sensitivity. It is observed that phenol, 4-phenoxyphenol, methylphenol (para and meta), nitrophenol and most importantly, tetrahydrocannabinol, can be detected voltammetrically. Such a protocol is particularly attractive for roadside testing for cannabis in drug drivers.