A study of the electrochemistry of tryptophan, peptides containing tryptophan, and related compounds (indoles) at mercury electrodes

Daryl J. Tucker, Alan M. Bond, Zhang Qing, Donald E. Rivett

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The electrochemistry of nineteen indole compounds of the general formula {A figure is presented} has been studied at mercury electrodes by differential pulse polarography, dc polarography, cyclic voltanunetry, cathodic stripping voltammetry, electrocapillary curves and controlled potential electrolysis in aqueous buffered media. Provided R1 = H, and the double bond is present between R2 and R3, a reversible oxidation process is observed at mercury electrodes which involves the formation of a mercury(II)-indole complex. Analysis of the wave shape, pH dependence, and concentration dependence of the oxidation process leads to the conclusion that the overall reaction is described by the equation 2InH + Hg ⇌ HgIn2 + 2H+ + 2 e- (process 1) where InH = indole with R1 = H. For some compounds a surface controlled second oxidation process is observed at more positive potentials than process one when high concentrations of indole are used. The presence of reactant and product adsorption is revealed by electrocapillary curves, cyclic voltammetric experiments and by the concentration dependence. Strong product adsorption can be used as the basis of a highly sensitive, but non-specific method for the determination of indole by differential pulse cathodic stripping voltammetry.

Original languageEnglish
Pages (from-to)127-146
Number of pages20
JournalJournal of Electroanalytical Chemistry
Issue number1
Publication statusPublished - 24 Mar 1989

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