title: Hydrogen peroxide-induced oxidation of mixtures of alkanethiols and their quantitative detection as alkanesulfonates by electrospray ionization mass spectrometry.
abstract: Finding optimal experimental conditions for generating stable negative ion electrospray ionization ion trap mass spectra (ESI-IT-MS) of alkanethiol-derived species is critical for quantitatively characterizing multicomponent alkanethiol-based self-assembled monolayers by this technique. Since alkanethiolates slowly oxidize in solution, purposeful oxidation of alkanethiols to their fully oxidized form (alkanesulfonates) is advantageous: sulfonates are chemically stable and have little affinity for covalent binding to metal surfaces. We have used ESI-IT-MS to characterize the products of H(2)O(2) oxidation of simple n-alkanethiols in solution and have observed monomeric alkanesulfonate species as well as alkanesulfonic acid/alkanesulfonate adducts, yielding gas-phase dimers and trimers. MS intensities of both monomers and adducts exhibit a dependence on the ion transfer capillary temperature that is alkyl-chain-length-dependent and that appears to be correlated with C-S bond cleavage. The trend in optimal capillary temperatures indicates that entropic effects lead to lower thermal decomposition temperatures for short-chain species relative to the longer-chain homologues. MS calibration data from alkanesulfonate mixtures are characterized by large linear dynamic ranges (10(-6)-10(-3) M) and detection limits influenced by their thermal decomposition. The high degree of precision in the calibration data should facilitate distinguishing among mixed SAMs having similar compositions.
authors: Department of Chemistry and Biochemistry, Samford University, Birmingham, Alabama 35229-2236, United States.
authors: Rachel
authors: R
authors: Roberts
authors: Joshua A
authors: JA
authors: Driver
authors: Danielle M
authors: DM
authors: Brown
authors: Sagar H
authors: SH
authors: Amin
authors: Brian W
authors: BW
authors: Gregory