Additively manufactured carbon/black-integrated polylactic acid 3Dprintedsensor for simultaneous quantification of uric acid and zinc in sweat

Abstract

For the first time the development of an electrochemical method for simultaneous quantification of Zn²⁺ and uric acid (UA) in sweat is described using an electrochemically treated 3D-printed working electrode. Sweat analysis can provide important information about metabolites that are valuable indicators of biological processes. Improved performance of the 3D-printed electrode was achieved after electrochemical treatment of its surface in an alkaline medium. This treatment promotes the PLA removal (insulating layer) and exposes carbon black (CB) conductive sites. The pH and the square-wave anodic stripping voltammetry technique were carefully adjusted to optimize the method. The peaks for Zn²⁺ and UA were well-defined at around - 1.1 V and + 0.45 V (vs. CB/PLA pseudo-reference), respectively, using the treated surface under optimized conditions. The calibration curve showed a linear range of 1 to 70 µg L^-1 and 1 to 70 µmol L^-1 for Zn²⁺ and UA, respectively. Relative standard deviation values were estimated as 4.8% (n = 10, 30 µg L^-1) and 6.1% (n = 10, 30 µmol L^-1) for Zn²⁺ and UA, respectively. The detection limits for Zn²⁺ and UA were 0.10 µg L^-1 and 0.28 µmol L^-1, respectively. Both species were determined simultaneously in real sweat samples, and the achieved recovery percentages were between 95 and 106% for Zn²⁺ and 82 and 108% for UA.

Keywords: 3D-printed electrodes; Carbon black; Electrochemical sensor; Electrode surface treatment; Square-wave anodic stripping voltammetry; Sweat analysis; Uric acid determination; Zinc determination.