Additively manufactured microplate for the simultaneous colorimetric and electrochemical detection of atropine

This work presents the development of a dual mode electrochemical and colorimetric sensing platform, produced in a single print through additive manufacturing. The cell design was based on the dimensions of a standard 96-well plate, with the base replaced by a disc electrode made from bespoke conductive polypropylene for the electrochemical testing, with the walls created from transparent non-conductive polypropylene to allow for the colorimetric tests. This new system was employed for the detection of atropine (ATP) in two distinct steps within the same electrochemical cell: (1) colour changes due to the reaction of ATP with bromocresol green, allowing for preliminary visual identification, and (2) the analysis of the electrochemical behaviour of the system before and after the colour change, providing quantitative confirmation. Both steps were performed in the same cell, highlighting the efficiency and practicality of the developed device. Wide linear ranges were obtained using square-wave voltammetry for ATP detection, spanning 0.65 to 20.83 mg mL^-1 before the colorimetric reaction, and 5.21 to 20.83 mg mL^-1 after the colorimetric reaction. Detection and quantification limits were calculated as 0.15 mg mL^-1 and 0.50 mg mL^-1, respectively, demonstrating suitability for real application in forensic scenarios. Beverage samples (energy drink, tonic water, gin, gin with tonic water, and whisky) and synthetic biological samples (saliva, urine, and vitreous humour) were spiked with ATP and analysed using the proposed method, yielding recoveries close to 100%, indicating no matrix effect. This study demonstrates the synergy between additive manufacturing, and electrochemical and colorimetric sensing to create real, functional sensing platforms that are applicable to a wide range of fields.