A dual colorimetric-electrochemical platform based on bromocresol green for the selective detection of atropine

Abstract

Atropine is crucial in forensic investigations due to its role in poisoning cases, requiring precise detection methods. We propose a novel dual-mode analytical platform that combines screen-printed graphite electrodes with square-wave voltammetry and a colorimetric reaction using bromocresol green. This dual platform provides three distinct analytical responses: a colour change via the colorimetric reaction and electrochemical responses before and after the colorimetric reaction, allowing robust atropine identification. For the first time, the electrochemical behaviour of atropine in the presence of bromocresol green has been investigated, with mechanistic insights elucidated through NMR analysis. Although atropine alone undergoes an irreversible oxidation process, the colorimetric reaction facilitates a redox process involving bromocresol green, allowing indirect atropine detection. The real-world applicability of this dual-sensing platform is demonstrated by detecting atropine in drink and biological samples for potential spiking and poisoning diagnosis. Importantly, the platform is shown to function within solutions containing quinine, proving its suitability to analysing strong and bitter tonic water drink with low atropine concentrations, overcoming this known analytical problem. The developed method exhibited a wide linear range (0.001–0.4 mg mL⁻¹), a low limit of detection (0.255 μg mL⁻¹), and excellent stability with relative standard deviation lower than 7 %. Interference studies confirm the method’s selectivity, and atropine recoveries from drink and biological samples were close to 100 %. The proposed platform is a simple, rapid, and selective screening tool, and shows significant potential for forensic applications in atropine detection.