Thiols polarography

The various oxidation states of sulfur have been determined by polarography. The electrochemical oxidation of sulfide ions in aqueous solution may lead to the production of elementary sulfur, polysulfides, sulfate, dithionate, and thiosulfate, depending on the experimental conditions. Disulfides, sulfoxides, and sulfones are typical polarographically active organic compounds. It is also found that thiols (mer-captans), thioureas, and thiobarbiturates facilitate oxidation of Hg resulting thus in anodic waves. 

The cavity of diphenylglycoluril derivative 3 is well suited to partially encapsulate a [4Fe-4S] cluster. Compound 29 which contains four arms terminating with thiol groups was synthesized and treated with (n-Bu)4N 2 Fe4S4Cl4) in dimethylformamide to give cluster complex 30 [31]. The product was characterized by a number of techniques, including cyclic voltammetry and differential pulse polarography. The current response of 30 was very small, but improved upon addition of a modulator, e.g. Ba or Na" ions. This behavior is similar to that observed for certain redox active enzymes [32]. As in the natural systems, a maximum response is observed when the Ba concentration is... 

Methods. In a recent study( ), polarography was used to determine Inorganic sulfur species in marine porewaters as in Tables I and II. In that study, no thiols or organic polysulfides were detected... 

Polarography of thiols. In an effort to duplicate the field results, several thiols which are commercially available were studied. The compounds were prepared in the pH 10 matrix which is used for the porewater analysis. The half-wave potentials are given for O.lmM solutions of each compound in pH 10 buffer. Our... 

The polarography of thiols is characterized by an anodic wave which often is well defined although, as for instance in the case of cysteine, the shape of the polarogram depends strongly on pH and buffer. Kolthoff and Barnum showed that the anodic wave of cysteine is due to the formation of mercurous mercaptide (HgSR), i.e. to the oxidation of the electrode and not of the thiol. Complications may arise when the reaction product is insoluble in the medium and covers the electrode. ... 

C.A. Mairesse-Ducarmois, G.J. Patriarche and J.L. Vandenbalck, Contribution a relectrochimie des thiols et disulfures Partie II. Polarographie d.c., a.c. et impulsionnelle differentielle du glutathion. Anal Chim. Acta, 1975,76,299-308. 

Pulse polarography and stripping voltammetry are considered as methods of choice for the quantification of environmentally significant organic molecules (carbonyls, nitroaromatics, phenols, carboxylic acids, sulfonates, azomethines, thiols, amines, etc.) using electrochemical sensors with chemical recognition [28]. The current capabilities of biosensors for organic pollutants analysis are discussed by [7]. 

Several examples of the applications of polarography in these fields have been already mentioned in Chapters VI and VII, viz. determinations of benzene, toluene, naphthalene and phenols in the atmosphere, breath, blood or urine, of amino acids (with particular interest to tyrosine, tryptophane, phenylalanine, histidine and histamine), of ketoacids, ketosteroids, carbon disulphide in air and blood, ethanol, acetoin, sugars and morphine in blood, of lactic acid, mandelic acid in bile and urine, adrenaline and thyroxine in iodinated proteins and last, but not least, of thiol compounds, both soluble and bound in biological materials. A few further examples will be given here. 

Vinylpyridines are basic they have an intensive smell and are soluble in common organic solvents. Since they have a high tendency to polymerize, they have to be stabilized for storing and transportation. Typical stabilizers are amines, phenols, thiols, and polysulfides. Their purity is determined by means of double-bond analysis [546], polarography [547], UV spectroscopy [548], and gas chromatography [549]. 

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