Local removal of oxygen for NAD(P)+ detection in aerated solutions

Electroanalytical Trace Metal Cations Quantification and Speciation in Freshwaters: Historical Overview, Critical Review of the Last Five Years and Road Map for Developing Dynamic Speciation Field Measurements

An historical overview covering the field of electroanalytical metal cations speciation in freshwaters is presented here, detailing both the notable experimental and theoretical developments. Then, a critical review of the progress in the last five years is given, underlining in particular the improvements in electrochemical setups and methodologies dedicated to field surveys. Given these recent achievements, a road map to carry out on-site dynamic metal speciation measurements is then proposed, and the key future developments are discussed. This review shows that electroanalytical stripping techniques provide a unique framework for quantitatively assessing metals at trace levels while offering access to both thermodynamic and dynamic features of metal complexation with natural colloidal and particulate ligands.

Amperometric Sensor for Selective On-Site Analysis of Free Sulfite in Wines

Accurate and rapid on-site analysis of free SO₂ content is crucial in the process of winemaking from a producer and consumer perspective. Herein, we present an amperometric sensor based on commercially available screen-printed electrodes coupled with an electrochemical oxygen filter. The developed amperometric method gave a linear response in a concentration range up to 200 mg L^-1 with a limit of quantification of 7.5 mg L^-1. The applicability of the developed sensor was successfully tested on 27 white and red wine samples and compared to the Ripper method (iodometry) that is a standard procedure for free SO₂ determination. The sensor exhibits similar precision and accuracy but shows no interference from oxidizable species such as ascorbic acid, which is a major advantage over iodometric titration. The performance of the sensor was in addition positively evaluated during on-site analysis in a winery.

Electroanalytical metal sensor with built-in oxygen filter

A rapid and reliable oxygen elimination system was evaluated here for the electroanalytical study of metals. Dissolved oxygen was removed locally in the vicinity of a sensor by the means of electrochemical oxygen filter constructed from platinum grids. Three metals (Cd, Pb, and Zn) were determined by stripping chronopotentiometry (SCP) at a mercury film screen-printed electrode. Limits of detection of metals were in the nanomolar range under optimized experimental conditions. The electrochemical device was also tested for metal quantification in simple electrolyte solutions and in a natural water matrix. The proposed combination of oxygen elimination system with the metal sensor completely removes the need to purge the sample before SCP measurement. This makes the determination of metals by SCP faster, portable and more suited for on-field applications.