title: Reduction of organic dyes in matrix-assisted laser desorption/ionization and desorption/ionization on porous silicon.
abstract: Reduction of analytes in matrix-assisted laser desorption/ionization (MALDI) often obscures the actual determination of molecular structure. To address the redox reactions in laser desorption/ionization processes, the organic dyes Methylene Blue, Janus Green B, Crystal Violet and Rhodamine B were analyzed by MALDI or by desorption/ionization on porous silicon (DIOS). Susceptibility to reduction in MALDI was dependent on both the reduction potentials of analytes and the molar ratio of analyte to matrix molecules. Addition of Cu(II) ions as an electron scavenger suppressed the reduction of Methylene Blue in MALDI. The results suggested that electron transfer to analytes from the sample target and/or from the matrix contributed to the reduction. In DIOS, the reductions of organic dyes were more prominent than in MALDI, and were not prevented by Cu(II) ion doping, probably due to direct contact of the analytes with silicon which had little electric resistance.
authors.affiliation: Japan Science and Technology Agency, Innovation Plaza Osaka, Wada Project Laboratory, 3-1-10 Technostage, Izumi, Osaka 594-1144, Japan. shoji-okuno@osaka.jst-plaza.jp
authors.forename: Shoji
authors.initials: S
authors.lastname: Okuno
authors.forename: Motohiro
authors.initials: M
authors.lastname: Nakano
authors.forename: Gen-etsu
authors.initials: GE
authors.lastname: Matsubayashi
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Wada
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D005840:Gentian Violet / Q000737:chemistry; D008751:Methylene Blue / Q000737:chemistry; D046208:Microchip Analytical Procedures; D009930:Organic Chemicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D012235:Rhodamines / Q000737:chemistry; D012825:Silicon / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D009930:Organic Chemicals; D012235:Rhodamines; C005086:Janus Green B; D005840:Gentian Violet; C029773:rhodamine B; D008751:Methylene Blue; D012825:Silicon