Toward the Analysis of Electrochemically Modified Self-Assembled Monolayers. Electrospray lonization Mass Spectrometry of Organothiolates

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Electrospray ionisation mass spectrometry (ESIMS) is investigated as a possible technique for the analysis of a variety of thiolates. Our future work will deal with thiolates, particularly polymeric ones, obtained from the electrochemical reductive desorption of alkanethiol self-assembled monolayers (SAMs) on metal surfaces. Such electrochemical methods of removing SAMs require high concentrations (10-2 M) of electrolytes like sodium methoxide. Thus, initial studies of model thiolates in the presence of electrolyte salts are reported here. Reproducible ESI spectra of thiolates can be obtained with thiolate concentrations in the 10-5-10-6 M range in the presence of 10-3-10-2 M sodium methoxide. Air oxidation of thiolate solutions occurs rapidly, as noted by the observation of RSO2- and RSO3- ions within minutes of thiolate solution preparation. Dithiols are investigated as possible models of polymeric thiols. Questions regarding intramolecular disulfide formation and charge state are addressed. ESI spectra of several thiolates, including ω-substituted alkanethiolates (ferrocene and olefin), are presented.

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Analytical Chemistry

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