title: High ion yields of carbohydrates from frozen solution by UV-MALDI.
abstract: An aqueous acetonitrile solution containing oligosaccharides (maltopentaose and polysaccharides) and a matrix (2,5-dihydroxybenzoic acid) was frozen at 100 K for mass analysis using ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). Compared with conventional UV-MALDI (i.e., using a dry analyte/matrix mixture), a frozen solution generates more oligosaccharide ions and less fragments from postsource decay. Furthermore, the ion signal is long-lasting, and the analyte distribution features enhanced homogeneity. The ion generation efficiency for this procedure is 20-30 times greater than that for a conventional dried mixture. Interestingly, the percentages for maltopentaose fragmentation from postsource decay for the frozen samples are close to zero (<2%), as compared with the 17% and 40% values found for dried samples at low and high laser fluences, respectively. Comparisons with other UV matrixes (α-cyano-4-hydroxycinnamic acid and sinapinic acid) and ionic liquids (2,5-dihydroxybenzoic acid + pyridine and α-cyano-4-hydroxycinnamic acid + butylamine) were investigated, and possible mechanisms are discussed.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Liang
authors.forename: Po-Jul
authors.initials: PJ
authors.lastname: Chang
authors.forename: Yu-Jiun
authors.initials: YJ
authors.lastname: Lin
authors.forename: Yuan-Tseh
authors.initials: YT
authors.lastname: Lee
authors.forename: Chi-Kung
authors.initials: CK
authors.lastname: Ni
mesh_terms: D002241:Carbohydrates / Q000032:analysis / Q000737:chemistry*; D003080:Cold Temperature; D015925:Cryopreservation; D007477:Ions; D056951:Photoelectron Spectroscopy; D012996:Solutions / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D002241:Carbohydrates; D007477:Ions; D012996:Solutions