3D-printing in forensic electrochemistry: Atropine determination in beverages using an additively manufactured graphene-polylactic acid electrode

Atropine is a natural tropane alkaloid extracted from plants of the family Solanaceae and usually employed for medicinal purposes. Due to its action toward the acetylcholine receptors, atropine can be also used in criminal activities by poisoning beverages. Three-dimensional (3D) printing technology has become popular in electrochemistry as it provides low-cost electrodes in varied designs using conductive filaments. In this work, we demonstrated that 3D-printed graphene-polylactic acid (graphene-PLA) electrodes can detect atropine in contaminated beverages samples. A 3D pen was used to manufacture the electrode using customized acrylic substrates to guide the reproducible application of the fused graphene-PLA filament by the pen. The 3D-printed electrodes were electrochemically treated to expose the conductive sites within the polymeric matrix, which resulted in the great improvement of the analytical response of atropine. Electrochemical impedance spectroscopic confirmed the faster electron transfer after surface treatment. The surface changes were confirmed by scanning electron microscopic and infrared spectroscopic. Using square-wave voltammetric determination and based on the electrochemical oxidation of atropine at + 0.89 V (vs. Ag|AgCl|KCl(sat.)), a linear concentration range between 5 and 60 mu mol L-1, with a detection limit of 1 mu mol L-1 was obtained using a Britton-Robinson buffer solution (pH = 11) as supporting electrolyte. Different beverages (white wine, vodka, whisky and energy drink) spiked with known amounts of atropine were analyzed after dilution in electrolyte and recovery values between 104 and 120% were obtained. The obtained results demonstrated that 3D printing materials are an interesting alternative to produce electrochemical sensors that can be tailored for on-site determination of forensic targets in beverage samples.