Target analyte assisted sensitive electrochemical detection of cocaine on screen printed electrodes†

The use of cocaine leads to several severe health conditions, and overconsumption often leads to death. Currently, cocaine detection devices require incubation periods, highly trained personnel, and expensive practices not suitable for roadside applications. Herein, a novel electrochemical biomolecule-free sensor for cocaine detection in complex matrices is presented using the electroactive characteristics of the cocaine molecule that does not require any biomolecules or chemicals for detection. This study implements the cocaine-modified carbon working electrodes to detect cocaine using cyclic voltammetry in a buffer solution and human saliva. At optimized conditions, the proposed electrochemical sensor enabled the detection of cocaine with a limit of detection of 1.73 ng mL⁻¹ in PBS buffer (pH ∼7.4). Additionally, to facilitate detection in saliva, a machine learning strategy was introduced to analyze sensor analytical responses to overcome saliva-related complications in electrochemical sensing and challenges emanating from saliva-to-saliva variation. The data processing results allowed us to distinguish between cocaine concentrations ranging from 0 to over 50 ng mL⁻¹ in saliva with an accuracy of 85%. Further, the successful detection of cocaine in the presence of various interferences was achieved, revealing that the m-Z-COC sensor is highly specific and a promising sensor for the development of a roadside oral fluid cocaine detection kit.