Electrochemical characteristics of conductive carbon cement as matrix for chemically modified electrodes

Abstract

Electrochemical characteristics of conductive carbon cement as matrix for chemically modified electrodes Huang, X.; Pot, J.J.; Kok, W.T. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractConductive carbon cement (CCC) was evaluated as matrix material for the preparation of electrodes bulk-modified with electrocatalysts. For pure CCC electrodes the background current characteristics were examined. In acidic or neutral phosphate buffers the useful electrode potential range was from -0.3 to + 1.0 V vs. SCE, while in 0.1 mol l-' NaOH it was from -0.3 to + 0.7 V. The electrochemical reversibility of CCC electrodes was examined by measuring the standard rate constants for the reduction of hexacyanoferrate( III) and the oxidation of hydroquinone, using cyclic voltammetry (CV) and rotating disk experiments. The reversibility of a CCC electrode was comparable with that of a freshly polished glassy carbon electrode and better than that of carbon paste electrodes. CCC was used as matrix for the preparation of electrodes bulk-modified with cuprous oxide and cobalt phthalocyanine (CoPC). With a C&O-CCC electrode the oxidation potential of glucose, which shows sluggish kinetics at unmodified carbon electrodes, was strongly reduced. The kinetics of the mediated glucose oxidation has been studied with a rotating disk electrode. It was shown that at glucose concentrations higher than approximately 1 mmol 1-l the electrochemical regeneration of the catalyst becomes rate-determining. The Cu@-CCC modified electrode has been applied with a constant potential in flow-injection analysis for the determination of glucose. The long-term stability of the electrode was studied; repeated injections of a glucose solution during a period of 6 h yielded a relative standard deviation of the peak height of 1.8% (n = 57). In CV experiments the electrocatalytic activity of CoPC was shown for the oxidation of various compounds such as penicillamine, hydrazine and bile acids. Application of the CoPC-CCC electrode for the detection of bile acids in flow-through detection with a constant or pulsed potential failed, due to a rapid deactivation of the electrode.

Determination of sugars by liquid chromatography and amperometric detection with a cuprous oxide modified electrode

“…This is not what would be expected for a diffusion controlled process [16]. However, in previous studies with rotating-disk electrodes it was already found that the oxidation of glucose at the modified electrodes is at least partially controlled by reaction kinetics [15]. To eliminate the effect of flow rate on the peak dispersion, peak areas in FIA were also measured.…”

“…The Cu20/CCC working electrode (3 mm diameter) Was prepared as described previously [15]. For cyclic Voltammetry, a computerized Autolab electrochemical analyzer (ECO Chemie, Utrecht, The Netherlands) was Used.…”

“…Above 650 mV, the background current increased rapidly, due to the oxidation of hydroxide. In previous studies a Cu20-CCC electrode was examined for the determination of glucose [15]. The activity of the Cu20-CCC electrode towards the oxidation of other sugars was further examined here.…”

“…The oxidation of sugars at carbon electrodes is sloW, even at high potentials. However, a catalyst (mediator) can be used to modify the carbon electrode in order to lower the overpotentials and accelerate the oxidatio~ processes [4][5][6][7][8][9][10][11][12][13][14][15]. Researches have been mainly focused on compounds such as transition metal oxides and cona" plexes.…”

“…It can be easily performed by mixirlg the matrix material with the desired amount of catalyst to achieve a homogeneous electrode material [11][12][13][14][15]. In previous work we have shown that conductive carbota cement (CCC) is suited as matrix material [14,15] to prepare catalyst modified electrodes. CCC consists of a thick paste of graphite powder with polyacrylic agents in xylene.…”