Novel colorimetric-electrochemical methods for selective identification and quantification of Scopolamine in forensic analysis using screen-printed graphite electrodes and Dragendorff reagent

In forensic investigations, the detection of Scopolamine, popularly known as Burundanga or Devil’s Breath, is of significant interest due to its potential involvement in cases of attempted murder or suicide. Currently, no efficient screening methods exist for Scopolamine detection in such forensic contexts. This study presents a novel method combining screen-printed graphite electrodes (SPGE) with square-wave voltammetry (electrochemical step) and Dragendorff reagent (colorimetric step) to detect Scopolamine in drinks (gin, tonic water, whisky, and energy drinks) and biological samples (urine, saliva, and vitreous humor). The method provides two distinct analytical responses: a visible color change (from orange to yellow) via the colorimetric reaction, and the electrochemical behavior of Scopolamine in both anodic and cathodic scans, ensuring robust and accurate identification. For the first time, the electrochemical behavior of both redox processes of Scopolamine is investigated. The proposed method demonstrated a wide linear range (0.025-0.225 mg mL⁻¹ for the oxidation and 0.025–0.175 mg mL⁻¹ for the reduction process) with a low limit of detection of 5.0 μg mL⁻¹, making it suitable for forensic applications. Stability of the electrochemical response was studied with SPGE showing relative standard deviations (RSD) of less than 3 % for E_p and I_p across multiple electrodes (N = 3). Interference studies confirmed the method's high selectivity for Scopolamine detection. Additionally, Scopolamine was successfully identified in both beverage and biological samples with recoveries near 100 %, indicating the absence of matrix effects. The methodology using both electrochemical with a colorimetric approach presents a promising, rapid, and selective screening method for Scopolamine detection in forensic scenarios.