Disposable screen printed sensor for the electrochemical detection of delta-9-tetrahydrocannabinol in undiluted saliva

Background: Cannabis has an adverse effect on the ability to drive safely, therefore a rapid disposable test for Δ 9 -tetrahydrocannabinol (Δ 9 -THC), the psychoactive component of cannabis, is highly desirable for roadside testing. Results: A screen printed carbon electrode is used for the N-(4-amino-3-methoxyphenyl)-methanesulfonamide mediated detection of Δ 9 -THC in saliva. Mediator placed in an overlayer was galvanostatically oxidized and reacted with Δ 9 -THC to give an electrochemically active adduct which could be detected by chronoamperometric reduction. Detection of 25-50 ng/mL Δ 9 -THC spiked into undiluted saliva was achieved with a response time of 30 s. A trial of the sensors with four cannabis smokers showed sensitivity of 28 %, specificity of 99 % and accuracy of 52 %. Conclusions: Rapid electrochemical detection of Δ 9 -THC in undiluted saliva has been demonstrated using a disposable sensor, however the sensitivity is lower than acceptable. Further optimization of the assay and sensor format is required to improve the sensitivity of response to Δ 9 -THC.