The use of a gold disc microelectrode for the determination of copper in human sweat

A home-made nanoporous gold microsensor for lead(II) detection in seawater with high sensitivity and anti-interference properties

A nanoporous gold microelectrode (NPG-μE) was fabricated and used for Pb(II) detection in seawater samples via square wave anodic stripping voltammetry (SWASV). The Au microelectrode (Au-μE) was fabricated by embedding a gold microfiber into a Pasteur pipette, and its surface was further modified by an anodization-electrochemical reduction (A-ECR) method, yielding the NPG-μE. The fabricated electrodes were characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FE-SEM) for electrochemical and structural morphological investigations. SWASV results show a Pb(II) stripping peak at around -0.05 V vs. Ag/AgCl, sat. KCl, which is unusual for common Pb(II) detection (typically occurring at around -0.40 V) in anodic stripping voltammetry (ASV) analysis. The Pb(II) detection at less negative stripping potential is more beneficial. Hence, it exhibited anti-interference properties with Cd(II), which is attributed to the preferential deposition and stripping of the target analyte on the low-indexed crystal planes of the NPG structure. The calibration plot obtained by SWASV was linear in the concentration range of 0.1-10 μM, and the detection limit was found to be 57 nM (correlation coefficient of 0.9974). The NPG microsensor presented a 15-fold enhanced current response compared to Au-μE, with excellent sensitivity (27.2 μA μM-1 cm-2). The application of the NPG microsensor was examined by detecting Pb(II) in seawater samples, and a satisfactory performance was obtained.

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

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.

Electroanalytical Sensor Based on Gold-Nanoparticle-Decorated Paper for Sensitive Detection of Copper Ions in Sweat and Serum

The growth of (bio)sensors in analytical chemistry is mainly attributable to the development of affordable, effective, portable, and user-friendly analytical tools. In the field of sensors, paper-based devices are gaining a relevant position for their outstanding features including foldability, ease of use, and instrument-free microfluidics. Herein, a multifarious use of filter paper to detect copper ions in bodily fluids is reported by exploiting this eco-friendly material to (i) synthesize AuNPs without the use of reductants and/or external stimuli, (ii) print the electrodes, (iii) load the reagents for the assay, (iv) filter the gross impurities, and (v) preconcentrate the target analyte. Copper ions were detected down to 3 ppb with a linearity up to 400 ppb in standard solutions. The applicability in biological matrices, namely, sweat and serum, was demonstrated by recovery studies and by analyzing these biofluids with the paper-based platform and the reference method (atomic absorption spectroscopy), demonstrating satisfactory accuracy of the novel eco-designed analytical tool.