title: Elucidation of molybdosilicate complexes in the molybdate yellow method by ESI-MS.
abstract: The formation of molybdosilicate in the molybdate yellow method is elucidated by ESI-MS. Polymeric silicic acids were hydrolyzed to monomers, and molybdosilicates with a Keggin structure were formed. Each step of the formation reaction of molybdosilicate from molybdic and silicic acids between pH 1 and 2 was clarified by ESI-MS at the molecular level. In a solution below pH 0.5, the polymers of the molybdic acids were decomposed because of the high concentration of sulfuric acid. Excess sulfuric acid prevented the formation of molybdosilicate. Thus, none of the silicic acids reacted to form molybdosilicate at this pH, despite the presence of silicic acid and sulfate ions in the solution. Above pH 2, the condensation of molybdic acids occurred to form α-molybdosilicate. ESI-MS provides information on the formation of molybdosilicate and the individual reaction species present in the reaction mixture.
authors.affiliation: Division of Marine Science, Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Konan, Minato-ku, Tokyo 108-8477, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Faculty of Pharmacy, Keio University, Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Abe
authors.affiliation: Division of Marine Science, Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Konan, Minato-ku, Tokyo 108-8477, Japan. Electronic address: mihotnk@kaiyodai.ac.jp.
authors.forename: Miho
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000032:analysis* / Q000138:chemical synthesis*; D011108:Polymers / Q000737:chemistry*; D012824:Silicic Acid / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D009942:Organometallic Compounds; D011108:Polymers; D012824:Silicic Acid; D008982:Molybdenum; C581523:molybdic acid
keywords: Electrospray Ionization Mass Spectrometry (ESI-MS); Molybdate yellow; Molybdosilicate; Silicic acid; pH dependence