Electrochemical Detection of Cocaine in Authentic Oral Fluid †

Abstract

Illicit drug consumption remains a problem to public safety and health, with abuse of illicit drugs having increased significantly over the last years. A concern related to this abuse is driving under the influence of drugs (DUID). Currently, police and law enforcement agencies rely on the use of lateral flow immunoassays (LFAs), which suffer from a lack of specificity. In this report, we present a rapid, sensitive, and affordable electrochemical method for the detection of cocaine in oral fluid (OF) by square-wave adsorptive stripping voltammetry on screen-printed electrodes (SPE). For the first time, the effects of the OF matrix on the electrochemical sensing of cocaine are deeply explored. The interference of endogenous compounds in OF, cutting agents and adulterants is studied. Interestingly, the electrochemical signal for cocaine is shown to be partially suppressed by the biofouling properties of albumin and most probably other proteins present in the OF matrix. Thus, strategies to mitigate these biofouling properties are explored. Subsequently, two sampling methods for OF, expectoration and the use of a commercial OF collection device (i.e., the Intercept i2), are investigated. The developed method shows promising potential in point-of-care testing for recent illicit drug use.