Electrode gold amalgam

Strides and Kolthofif using DC polarography found that between pH 1 and pH 10.5 and at ca -0.25 V vj SCE, Reaction 5.2 also applied to GSH. Mairesse-Ducarmois et showed that following the oxidation of GSH, the product, GSHg, was adsorbed onto the mercury surface. Similar results have been observed with silver electrodes. Gold amalgam electrodes can also be used (see below). 

ICP-SFMS (Thermo Finnigan, Flement) with cold vapour generation was developed with a guard electrode and a gold amalgamation device using an Au-sorbent for sample pre-concentration to improve the sensitivity. Instrumental parameters of ICP-SFMS such as take-up time, heating temperature of Au-sorbent, additional gas flow, and sample gas flow were optimized. Detection limit calculated as 3 times the standard deviation of 10 blanks was 0,05 ng/1, RSD = 7-9 %. 

Potentiometric EDTA titrations are best carried out with a mercury pool electrode (Figure 5.6) or a gold amalgam electrode. When this electrode dips into a solution containing the analyte together with a small amount of added Hg-EDTA complex, three interdependent reactions occur. For example, at pH = 8 the half cell reaction (a) which determines the electrode potential is related to the solution equilibrium by (b) and (c). 

Figure 11.13 Voltammetric scans at gold amalgam electrodes for the reduction of C02 in dimethyl sulfoxide (a) Pt, N2 (b) Pt, 1 mM C02 (c) Hg(Pt), N2 (d) Hg(Pt), 1 mM C02. Electrode area 0.215 cm2, supporting electrolyte 0.03 M (Et4N)C104, scan rate 0.05 V s 1.

Three working electrode materials are commonly used in thin-layer amperometric detectors glassy (or "vitreous") carbon, carbon paste, and gold amalgamated with a thin film of mercury. 

Electrochemical properties of this heme-containing enzyme have been studied. The potentiodynamic curves measured on the gold amalgamated electrode in the presence of peroxidase in the electrolyte show two maxima— anodic and cathodic (Figure 9), near the potential E 0.10 V. Replacement of the test electrolyte with electrolyte containing no peroxidase did not lead to a change in the variation of charging curves. This points to the irreversible... 

Figure 9. i-E curves measured on the gold amalgamated electrode in the presence of peroxidase solution (2). (1) Background curve, pH = 6.9. 

Fadrna etal. [70] has proved that a polished silver solid amalgam electrode, free from liquid mercury, is a suitable substitute for the HMDE in CSV analyses of purine bases and of acid-treated ODNs. The analysis was done at nanomol level in alkaline medium in the presence of Cu(ll). Similarly, the application of gold amalgam-alloy electrode for a sensitive voltammetric detection of ODNs containing the purine units within the ODN chains in the presence of Cu(ll)... 

Gold amalgam electrodes have been successfully used with CZE for certain applications. Jin and Wang showed that a gold amalgam electrode used without... 

Kleinman and Richie used the in-series approach with gold amalgam electrodes to measure 12 thiols and disulfides, including GSH, GSSG, cysteine, cystine, homocysteine, homocystine and several mixed disulfides in rat tissues. The first (upstream) electrode was maintained at —1.0 V and the second (downstream)... 

Waite, T.J., Kraiya, C., Trouwborst, R.E. et al. (2006) An investigation into the suitability of bismuth as an alternative to gold-amalgam as a working electrode for the in situ determination of chemical redox species in the natural environment. Electroaruilysis, 18, 1167-1172. 

Noble-metal (Au, Pt) electrodes have been employed for special studies, and gold amalgam electrodes as well as mercury-film electrodes have been used for reductive determinations [44] - [46]. 

Baik SH, Kang C, Jeon IC, Yun SE (1999) Direct electrocheinical regeneration of NADH from NAD using cholesterol-modified gold amalgam electrod. Biotechnol Tech 13... 

Figure 3 Detection scheme for peptides containing cystine (RSSR) and cysteine (RSH) employing a dual gold amalgam working electrode system.

Direct, nonmediated electrochemical reduction of NADIP)" " at modified electrode surfaces has been used to produce the en2ymatically active NAD(P)H and even to couple the NAD(P)H regeneration process with some biocatalytic reactions [228]. The modifier molecules used for these purposes are not redox active and they do not mediate the electron-transfer process between an electrode and NAD(P)+ however, they can effectively decrease the required overpotential and prevent formation of the nonenzymatically active dimer product [228]. For example, the efficiency of the direct electrochemical regeneration of NADH from NAD" " was enhanced by the use of a cholesterol-modified gold amalgam electrode that hinders the dimerization of the NAD-radicals on its modified-surface [228]. This direct electrochemical NAD+ reduction process was used favorably to drive an enzymatic reduction of pyruvate to D-lactate in the presence of lactate dehydrogenase. The turnover number for NAD" " was estimated as 1400 s k Other modifiers that enhance formation of the enzymatically active NAD(P)H include L-histidine [229] and benzimidazole [230], immobilized as monolayers on silver electrodes. CycKc voltammetric experiments demonstrated that these modified electrodes can catalyze the reduction of NAD+ to enzymatically active NADH at particularly low overpotentials. 

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