A simple graphene modified electrode for the determination of antimony(III) in edible plants and beverage.

Antimony(III) is a rare electroactive specie present on Earth, whose concentration is not typically determined. The presence of high concentrations of antimony is responsible for a variety of diseases, which makes it desirable to find convenient and reliable methods for its determination. We have developed a convenient glassy carbon modified electrode with electroreduced graphene oxide GC/rGO for the first time determination of Sb(III) in commercial lettuce, celery, and beverages. The surface of the electrode was characterized by scanning electron microscopy (SEM) and cyclic voltammetry, indicating a heterogeneous and rough surface with a real area of 0.28 cm2, which is ~2.5 times the area of GC. The optimal chemical and electrochemical parameters used were: sodium acetate buffer (pH = 4.3), an accumulation potential of -1.0 V and an accumulation time of 150 s. The analytical validation was developed evaluating the linear range (10-60 µg L-1), limit of detection (2.5 µg L-1), accuracy, repetibility and reproducibility with satisfactory results (relative standard deviation (RSD) values lower than 10%). All the analyzes performed in real samples by stripping voltammetry were compared with GF-AAS, showing statistically similar values, demonstrating that GC/rGO could be effectively applied in the analysis of food samples.

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.

Simultaneous metal determination in artisanal cachaça by using voltammetry and multivariate calibration.

In this study, square wave anodic stripping voltammetry using two different types of electrodes (carbon nanotube electrode and graphite electrode) was combined with chemometric methods - partial least squares (PLS) and artificial neural networks (ANN) for determining copper, zinc, cadmium and lead in cachaça. The objectives were comparison of methods developed and the verification of the quality of artisanal cachaças in terms of metal content. For the development of the methodology, inductively coupled plasma optical emission spectrometry (ICP OES) was used as reference technique. The performance of multivariate models obtained was evaluated by the coefficient of determination (R2) and root mean square error of prediction (RMSEP). F test was utilized for comparing methods at confidence level of 95%. Better results were observed by using carbon nanotube electrode regardless of the multivariate method proposed. The methodology is simple, fast, and inexpensive and it can be used in quality control laboratories.