Illicit drug consumption remains a problem to public safety and health, with abuse of illicit
drugs having increased significantly over the last years.^[1] 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),^[2] which suffer from a lack of specificity.^[3]
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 and 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. 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.

References:
(1) United Nations Office on Drugs and Crime (UNODC). World Drug Report 2021; 2021.
(2) Ahmed, S. R.; Chand, R.; Kumar, S.; Mittal, N.; Srinivasan, S.; Rajabzadeh, A. R. Recent
Biosensing Advances in the Rapid Detection of Illicit Drugs. TrAC - Trends Anal. Chem. 2020,
131, 116006. https://doi.org/10.1016/j.trac.2020.116006.
(3) Posthuma-Trumpie, G. A.; Korf, J.; Van Amerongen, A. Lateral Flow (Immuno)Assay: Its
Strengths, Weaknesses, Opportunities and Threats. A Literature Survey. Anal. Bioanal. Chem.
2009, 393 (2), 569–582. https://doi.org/10.1007/s00216-008-2287-2.