title: Electrospray mass spectrometry of hydrophobic compounds using dimethyl sulfoxide and dimethylformamide as solvents.
abstract: The use of dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) as solvents in electrospray ionization (ESI) is suggested for the analysis of hydrophobic compounds. Its use was shown to overcome solubility problems and resulted in good quality electrospray spectra of protected hydrophobic peptides, sugars and other hydrophobic compounds. Intense protonated and/or sodiated molecules were formed in positive ion mode while negative ion mode resulted in [M + 95](-) ions from DMSO and [M + Cl](-) ions from DMF in cases where no significant molecular ion related peaks could be observed applying commonly used protic solvents such as methanol or acetonitrile. Deuterium labeling (d6-DMSO), high resolution experiments and tandem mass spectrometric measurements showed that the methanesulfonic acid (MSA), present in DMSO as a common impurity, is responsible for the formation of protonated molecules in positive ion mode and for methane sulfonate anion adducts [M + 95](-) in negative ion mode.
authors.affiliation: Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary. szabop@chemres.hu
authors.forename: P T
authors.initials: PT
authors.lastname: Szabó
authors.forename: Z
authors.initials: Z
authors.lastname: Kele
mesh_terms: D000595:Amino Acid Sequence; D001555:Benzene Derivatives / Q000032:analysis*; D002241:Carbohydrates / Q000032:analysis*; D004121:Dimethyl Sulfoxide; D004126:Dimethylformamide; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis*; D012997:Solvents; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001555:Benzene Derivatives; D002241:Carbohydrates; D010455:Peptides; D012997:Solvents; D004126:Dimethylformamide; D004121:Dimethyl Sulfoxide