Novel low-cost instrumentation based on an RGB sensor using molecularly imprinted polymers (MIPs) for the rapid detection of aqueous 2-methoxphenidine (2-MXP)

Abstract. In this paper, we demonstrate a novel, cost-effective sensing system utilizing a molecularly imprinted polymer (MIP) for the indirect colorimetric detection of 2-methoxphenidine (2-MXP). Unlike other colorimetric methods that often require expensive spectrometers and bulky read-out equipment, our system is streamlined, employing basic components such as a digital RGB colour sensor, a white LED, and a 3D-printed opaque enclosure compatible with standard spectrometer cuvettes. The sensor is constructed from readily available commercial components using conventional manufacturing processes. Our approach is versatile, accommodating various liquid analytes, making it suitable for diverse applications, including rapid toxicological screening. To this end, optimization towards the dwell time, number of assays needed, and a dose response for the methodology are explored. Specifically, we focus on the detection of 2-MXP in an aqueous solution within a concentration range of 0.05 to 1 mM. Within range, our system effectively identifies the presence of the analyte and quantifies its concentration. Notably, we achieved a detection limit as low as 0.026 mM, which corresponds to a typical metabolite concentration observed in humans. These results underscore the potential of our prototype sensor for practical applications in the rapid and economical field of diagnosis of MXP intoxication.