Studying the ion transfer across liquid interface of thin organic-film-modified electrodes in the presence of glucose oxidase

Abstract

A coupled electron-ion transfer reaction at thin organic-film-modified electrodes (TFE) is studied in the presence of glucose oxidase (GOx) under voltammetric conditions. TFE consists of a graphite electrode modified with a nitrobenzene solution of decamethylferrocene (DMFC) as a redox mediator and tetrabuthylammonium perchlorate as an organic-supporting electrolyte, in contact with aqueous buffer solutions containing percholarte ions and GOx. The redox turnover of DMFC coupled with perchlorate transfer across water|nitrobenzene interface composes the coupled electronion transfer reaction. Glucose oxidase strongly adsorbs at the liquid|liquid interface affecting the coupled electron-ion transfer reaction by reducing the surface area of the liquid interface, prompting coadsorption of the transferring ion and lowering down slightly the rate of the ion transfer reaction. Although the enzyme exists as a polyvalent anion over the pH interval from 5.6 to 7, it does not participate directly in the ionic current across the liquid interface and percholrate remains the main transferring ion. Raman spectroscopic data, together with the voltammetric data collected by three-phase droplet electrodes, indicate that the adsorption of the enzyme does not depend either on the redox mediator (DMFC) or the organicsupporting electrolyte, while being driven by intrinsic interactions of the enzyme with the organic solvent. The overall electrochemical mechanism is mathematically modeled by considering linear adsorption isotherm of the transferring ion, semi-infinite mass transfer regime, and phenomenological second-order kinetic model.

Electrochemistry of proteins at the interface between two immiscible electrolyte solutions

“…This measurement approach opens up the prospect to detect other biomarkers at biomedically-relevant concentrations by relying on their catalytic activity. Of course, the behaviour of enzymes at the ITIES has been the subject of study for a number of years, as exemplified by glucose oxidase [33][34][35][36][37] and cholinesterases [38,39].…”

“…However, electron transfers have also been explored for GOx and other enzymes from a fundamental viewpoint rather than seeking to develop a glucose biosensor. Georganopoulou et al [33] studied electron transfer between aqueous phase GOx and organic phase dimethylferricinium, while Mirceski et al [37] found coupled ionelectron transfer reactions for GOx and decamethylferricinium in a three-phase system. GOx adsorption at the ITIES was reported [34,37].…”

“…Georganopoulou et al [33] studied electron transfer between aqueous phase GOx and organic phase dimethylferricinium, while Mirceski et al [37] found coupled ionelectron transfer reactions for GOx and decamethylferricinium in a three-phase system. GOx adsorption at the ITIES was reported [34,37]. Similar observations were reported for fructose dehydrogenase [40], undergoing electron transfer reaction with organic phase dimethylferricinium, and with adsorption at the interface.…”

First Electroanalytical Studies of Profluralin with Square Wave Voltammetry Using Glassy Carbon Electrode

“…Electrochemical assay often offers selectivity and sensitivity due to the selective detection of electroactive species among the complex samples. Among electrochemical methods voltammetry , especially square wave voltammetry (SWV) , is the one which offers broad mechanistic, kinetic and analytical studies. In the present work the quantitative determination of PFL is studied for the first time under SW conditions.…”

“…However, up to date,t oo ur knowledge there is no electrochemical method dedicatedf or determination of this compound. Despite that fact in the literature exist many examples of non-enzyme electrodes for the detection of nitroorganophosphate pesticides [14][15][16][17].E lectrochemical assay ofteno ffers selectivity and sensitivity due to the selective detectiono fe lectroactive speciesa mong the complex samples.A mong electrochemical methods voltammetry [18][19][20],e speciallys quare wave voltammetry (SWV) [21],i st he one which offers broad mechanistic, kinetic [22][23][24] and analytical [25][26][27][28][29][30][31][32] studies.I nt he present work the quantitative determination of PFL is studied for the first time under SW conditions. Abstract:T he electrochemical behaviouro fp rofluralin (PFL) was investigatedw ith squarew ave voltammetry (SWV)a nd cyclic voltammetry at bare and modified with graphene,g raphene oxide,r educed graphene oxide, carbon nanotubes glassy carbone lectrode.T he influence of variousf actors such as pH, buffer composition, ionic surfactants and voltammetric parameters was studied.…”