CHEMICAL-SPECIES OF METHYLENE-BLUE AT INT ERFACIAL REGIONS BETWEEN GLASS-WATER, METHANOL, AND WATER-METHANOL MIXED-SOLVENT - FACTOR-ANALYSIS OF VISIBLE INTERNAL-REFLECTION SPECTRA

Visible internal-reflection and transmission spectroscopy was employed for examining chemical species of Methylene Blue (MB) at the glass-so lution interface, where the glass served as an internal-reflection ele ment, and in the bulk of the solution. Both spectra of MB in methanol solution agreed with each other, suggesting that MB exists as a monome r in the interfacial region as well as in the solution. On the other h and, the internal-reflection spectrum was qualitatively different from the transmission spectrum in aqueous solution. This fact suggests tha t MB exists as different species in the interfacial region, such as a highly aggregated and an adsorbed species. Further, sixteen internal-r eflection spectra of MB solutions differing in composition of water an d methanol were examined by factor analysis. As the result, three comp onent spectra were proposed and were assigned to a monomer in the meth anol solution, a monomer adsorbed by glass, and a dimer in the aqueous solution.