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The reduction potentials of some purine and pyrimidine bases and the guanine nucleoside and nucleotide at pH values between 7 and 13 were investigated using the techniques of cyclic voltammetry, differential pulse polarography, and pulse radiolysis. The results clearly show that the lowest reduction potentials, in volts vs NHE, at pH 7 are those of xanthine, 0.88 V, and 1-methylguanine, 1.06 V (NHE). The extrapolated value of guanine is ca. 1.0 V. We also studied the one-electron oxidation reaction of the azide radical with the above compounds. We monitored their transient absorption spectra and determined their formation secondorder rate constants. The decay kinetics of these radicals was followed. Radicals derived from the bases decayed via a radical-radical mechanism with a second-order rate constant. However, the guanine nucleosides and nucleotide radicals have shown at all pHs two consecutive processes (first order followed by a second order). The first-order reaction is pH dependent. Formation of a new transient was observed at pH g9 for guanosine, pH g11 for 2′-deoxyguanosine, and at pH 13 for 5′-GMP. The observed new transient spectra were similar to that observed for the oxidized guanine radical. Therefore, we suggest that in these oxidized guanine nucleosides and nucleotide the oxidized guanine radical has been released. As previously suggested our results imply that the radiation-induced base release from nucleosides in alkaline solution is due to the preferred reaction of the nucleoside sugar with O •-Using our results, those of Steenken et al.

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Cobalt tetra(4-NN'N''-trirnethylanilinium)porphyrin (CoTMAP) has been studied in aqueous solutions using cyclic voltammetry, differential pulse voltammetry as well as by RRDE and spectroelectrochemical methods. The CoI"/Co"TMAP couple dissolved in 0.05 rnol dm-3 H,SO, has a redox potential of +0.14 V. The A, , , of the Soret band are 427 and 412 nm for CoI" and CoIITMAP, respectively. The rate constant for the reaction between Co"TMAP and dioxygen in 0.05 rnol dmP3 H,SO, was estimated to be 3 x lo7 dm3 molP s-l. The Co'I'TMP has been found to absorb at monolayer levels on glassy carbon surfaces and to have a catalytic effect on dioxygen electroreduction in aqueous solutions. This catalytic effect is strongly dependent on electrolyte pH. The overvoltage of 0, reduction is reduced by 480mV and insignificant amounts of H,O, are produced at pH 1, while an overvoltage decrease of 300 mV and an H,O, yield of 70% are observed at pH 8.

Cyclic voltammetry is used to determine the concentration of water and hydrolysis products in a pelletized LiC1-KC1-MgO mixture. This method, effective at temperatures above the melting point of the electrolyte, completes other electrochemical and thermal methods which have been previously used to investigate the various states of water at lower temperatures. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-05 to IP ABSTRACT The purification by electrolysis at a mercury electrode of aqueous solutions of potassium chloride containing manganese ions is investigated. The concentration of manganese decreased from 112 to 0.4 ppm after 20 min of electrolysis at -1.85V (vs. SCE).The procedures reported over the last ten years to purify aqueous solutions of alkali metal chlorides involve the use of precipitating agents, ion-exchange resins, or both types of substances (1-18). Of these procedures, the great majority is focused on the elimination of calcium and magnesium ions present in the solution (5-9, 11-15, 17, 18).In this paper, the purification by electrolysis of aqueous solutions of potassium chloride contaminated with manganese is studied. This method of purification and ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199 Downloaded on 2015-06-05 to IP