title: Mass determination of phosphoramidites.
abstract: Nucleoside phosphoramidites are the most widely used building blocks in contemporary solid-phase synthesis of oligonucleotides. The accurate molecular weight measurements of such molecules, which are acid-labile compounds, may be easily determined by mass spectrometry using a matrix system, triethanolamine/NaCl, on a liquid secondary ion mass spectrometer (LSIMS) or fast-atom bombardment (FAB) MS equipped with a double-focusing mass spectrometer. The present method rapidly and easily measures the accurate molecular weights of various phosphoramidites as adduct ions [M+Na]+ with an average mass error smaller than 0.4 ppm, allowing determination of the formulas of the phosphoramidites in place of elemental analysis. Further, it was found that intensities of molecular-related ions could be enhanced to the highest degree by adjustment of the molar ratio of phosphoramidite and NaCl, fixing the amount of triethanolamine on LSIMS, making the present method a powerful tool for identification of phosphoramidites by mass spectrometry.
authors.affiliation: Osaka University of Pharmaceutical Sciences, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Harusawa
authors.forename: Mihoyo
authors.initials: M
authors.lastname: Fujitake
authors.forename: Takushi
authors.initials: T
authors.lastname: Kurihara
authors.forename: Zheng-Yun
authors.initials: ZY
authors.lastname: Zhao
authors.forename: David M J
authors.initials: DM
authors.lastname: Lilley
mesh_terms: D000577:Amides / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D008970:Molecular Weight; D010756:Phosphoric Acids / Q000737:chemistry*
chemical_list: D000577:Amides; D010756:Phosphoric Acids; C011067:phosphoramidic acid