Fostering and Understanding Iron Detection at the Ultratrace Level by Adsorptive Stripping Voltammetry with Catalytic Enhancement

Abstract

Iron detection at the ultratrace level in seawater is at the forefront in chemical oceanography research and analytical methodologies for its determination are actively sought. Voltammetric methods and specifically cathodic stripping voltammetry (CSV) with catalytic enhancement, are particularly fit for this purpose as they avoid any separation and pretreatment step, showing high sensitivity and robustness towards the saline matrix. Here we introduce a simplification in the instrumentation for iron detection by CSV using 2,3‐dihydroxynaphthalene (DHN) as the ligand, atmospheric oxygen as the catalytic enhancer and a small 0.5 mL cell. The simplification involves the use of a standard, non‐specialized voltammetric cup as a holder for the small cell and the introduction of a simple silver wire as a pseudoreference electrode. The latter reduces the risk of sample contamination and is perfectly suited for employment with the small, 0.5 mL volume cell. Extensive optimization was performed in both ultrapure and seawater: a square wave frequency of 10 Hz was adopted, whereas the ligand concentration did not significantly influence the limit of detection (around 10 and 40 pM for ultrapure and seawater, respectively). The latter difference in signal to noise ratio was explained by the kinetics of iron complex reduction. The method was successfully validated by the analysis of a seawater sample with consensus value.

Advancements in Portable Voltammetry: A Promising Approach for Iron Speciation Analysis

“…Differential pulse voltammetry (DPV), Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV) are the most commonly used techniques [17][18][19][20][21]. A wide range of complexing agents have been used, such as 1-nitroso-2-naphthol (NN) [22], 4,4 -[3-(2-pyridyl)1,2,4-triazine-5,6diyl]bis(benzene sulfonic acid) disodium salt hydrate (ferrozine, FZ) [23], dihydroxynaphthalene (DHN) [24,25], 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) [26] and 2-(2-thiazolylazo)-p-cresol (TAC) [27]. Another fundamental aspect is the use of suitably modified working electrodes (WE); in the literature, there are some important examples, such as chemically modified carbon-paste electrodes (CMCPEs) [28,29], nafion-coated electrodes (NCE) [30], thick-film graphite containing electrode modified with calomel (TFGME) [31], boron-doped diamond (BDD) electrodes [32], bismuth-coated glassy carbon electrodes (BiFE) [33,34], gold and bismuth bimetallic nanoparticles decorated with Lcysteine-functionalized graphene oxide nanocomposites (Au-BiNPs/SH-GO) [35] and gold 2-mercaptosuccinic acid self-assembled monolayers (AuMSA SAM) [36].…”

A modular platform based on electrospun carbon nanofibers and poly(N‐isopropylacrylamide) hydrogel for sensor applications

“…Moreover, significant efforts have been made to simplify the equipment and/or the methodology for electrochemical sensing analytes 42–46 . Methods based on anodic stripping voltammetry or adsorptive cathodic stripping have shown good sensitivity even with samples at low concentration inside complex matrices (e.g., saline matrix) 47,48 . Nevertheless, those methods show interference by organic matter due to electrode fouling.…”

“…[42][43][44][45][46] Methods based on anodic stripping voltammetry or adsorptive cathodic stripping have shown good sensitivity even with samples at low concentration inside complex matrices (e.g., saline matrix). 47,48 Nevertheless, those methods show interference by organic matter due to electrode fouling. While a chemical digestion step could be used to remove organic matter, it makes the analytical procedure more complex and precludes the use of sensors in the field.…”

Sensitive Quantification of Fe(III) in Food Samples at Screen Printed Carbon Electrode Modified with Graphene and Piroxicam by Catalytic Adsorptive Voltammetry

“…Electrochemical methods in which electroactive analytes adsorb or accumulate on the electrode surface as well as methods based on the use of catalytic reactions, Faradic current prominently increases. Catalytic mechanisms by a cyclic reaction at the electrode surface are irreversible and often the electrochemical methods which are less sensitive to a reversible process such as differential pulse voltammetery, have been applied for evaluating the analytical response [28][29][30].…”