On-Line Linear Sweep Voltammetry−Electrospray Mass Spectrometry

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Abstract
A three-electrode electrochemical cell coupled to an electrospray (ES) mass spectrometer has been developed and employed for on-line linear sweep voltammetry-ES mass spectrometry and electrochemical reaction studies. Generated in this type of electrochemistry/mass spectrometry (EC/MS) experiment are ion abundance vs potential profiles that provide molecular weight and structural information pertaining to intermediates and products of anodic oxidation of diphenyl sulfide, anodic pyridation of 9,10-diphenylanthracene, and reduction of nitrobenzene. Anodic oxidation of diphenyl sulfide in methylene chloride media at the platinum electrode yielded diphenyl sulfoxide and pseudodimer sulfonium ion along with products of further oxidation. The obtained ion abundance vs potential profiles offer additional evidence to corroborate previously proposed reaction mechanisms for pseudodimer sulfonium ion generation from diphenyl sulfide, as well as pyridine addition to DPA radical cation also in methylene chloride at the platinum electrode. From the latter experiment, a newly found reaction product, [DPA(py) - H](+), is reported. Despite the inherent tendency of ES devices to induce oxidation processes in the positive ion mode, intermediates and products of nitrobenzene reduction in nonaqueous and organic/water media were detected in both negative and positive ES modes.