A fundamental analysis of a metal reduction process is important for the development on metal plating, electric refining, and nanoparticle synthesis. Electrochemical and spectroelectrochemical methods have been applied for the mechanistic analysis of the noble metal nanoparticles formation as well as the actinide reduction. Ionic species and electron transfer reactions at the interface between aqueous and organic solutions were measured by charge transfer voltammetry at the liquid|liquid interface. Chemical status and redox characteristics of actinide ions in various solutions such as water, organic solutions, molten salts, highly concentrated electrolytes were studied by electrochemical methods combined with in-situ X-ray absorption spectroscopy.

Electroanalytical methods are known to be quite useful for various analyses of biologically relevant materials. The author has attempting to clarify the advantages of electroanalytical methods and to elucidate the functions and properties of biological samples using electrochemical methods. This paper provides an overview of the author’s electrochemical studies focusing on oxidoreductases and polyamino compounds.

Determinations of bioactive compounds were carried out by various electrochemical detections (ECDs) hyphenated with high-performance liquid chromatography (HPLC-ECD) systems. An HPLC-ECD using a capillary column (0.2 mm i.d.) achieved determinations of catechins at femtogram levels. A three-channels HPLC-ECD using a column switching technique provided to the simultaneous determination of caffeoylquinic acids and flavonoids in Chrysanthemum morifolium flowers. HPLC-ECD systems by the means of reduction of 3,5-di-tert-butyl-1,2- benzoquinone and oxidation of trolox were developed to determine polyunsaturated fatty acids and theophylline in plasma, respectively. These HPLC-ECD systems with sensitivity and precision produced a practically useful method for the analyses of biological and herbal medicine samples.

English Abstract: In this report, two applications of chemometrics to electroanalytical chemistry are presented. In addition to potential and electric current, other information such as heat evolution of electrode reaction or Raman spectral peak analysis of specific species gives many useful information to figure out reactions and species. The electrochemical heat evolution is related to the entropy change of the reaction so that two different electrochemical reactions with different entropy change can be easily separated. But, a quantity we measure is temperature change of the electrode, which is delayed from real heat evolution due to heat capacity and so on. So the measured temperature change has to be deconvoluted to the true heat evolution by a mathematical method using the delay function. Another example of the deconvolution technique is to measure the Raman spectral peak of specific species to estimate its spatial change of the concentration in solution from the electrode surface by using a focal depth profile of the objective lens used in Raman microscope technique as a window function.