Additive manufacturing of a portable electrochemical sensor with a recycled conductive filament for the detection of atropine in spiked drink samples

Arantes, Iana VS, Crapnell, Robert D ORCID: https://orcid.org/0000-0002-8701-3933, Whittingham, Matthew J, Sigley, Evelyn, Paixão, Thiago RLC and Banks, Craig E ORCID: https://orcid.org/0000-0002-0756-9764 (2023) Additive manufacturing of a portable electrochemical sensor with a recycled conductive filament for the detection of atropine in spiked drink samples. ACS Applied Engineering Materials, 1 (9). pp. 2397-2406. ISSN 2771-9545

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Abstract

Additive manufacturing (three-dimensional (3D) printing) has promising features for fast prototyping electrochemical systems, from cells to sensors. Conductive filaments containing carbon black and poly(lactic acid) (CB/PLA) for electrode fabrication are commercially available but usually rely on low carbon content, resulting in poor electrochemical properties. Filament fabrication can be done within the laboratory by exploring different materials according to the desired applications. In this work, recycled PLA was used as the thermoplastic base polymer, alongside CB as the conductive filler, and tris (2-ethylhexyl) trimellitate was introduced into the filament matrix as a plasticizer (CB/PLA/TTM) to fabricate additively manufactured electrodes (AMEs). This enhanced the electrochemical properties toward different redox probes and the forensic target atropine. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the filament and AMEs before and after activation. Additive manufacturing has also been used to develop different cell configurations, which is equally important for good electroanalytical performance. Flow analytical techniques, such as batch-injection analysis (BIA), can be used as an alternative to stationary measurements to enhancing sensitivity and detection limits (LOD) via increasing the mass transport of analytes to the electrochemical platform surface, providing automation and high sample throughput. In this context, we developed a compact (∼5 mL capacity) and versatile additively manufactured BIA cell that can either perform static or hydrodynamic analyses by simply placing a lid on the device with a hole for the BIA pipette tip. Moreover, knowing that forensic chemistry necessitates portable analytical tools to help police investigation at the crime scene, the AM-BIA cell and the bespoke AMEs were coupled to a portable electrochemical apparatus for on-site atropine analysis in adulterated beverage samples. Atropine determination was performed by differential pulse voltammetry (DPV) and amperometry (BIA-AMP) in the same cell, presenting good repeatability for both methods (6% RSD). As expected, the BIA-AMP method showed higher sensitivity (0.0783 μA μM–1) and lower LOD (0.51 μM) compared to the stationary DPV method (sensitivity: 0.0148 μA μmol–1 L; LOD: 2.60 μM); they both presented good recovery values, varying from 102 to 109% for two spiked samples of gin and whisky. Thus, the versatility and portability of the developed AM-BIA cell coupled with the bespoke filament CB/PLA/TTM allow for rapid and accurate screening and quantification of atropine in real forensic scenarios.