On-line linear sweep voltammetry-electrospray mass spectrometry.

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Mass Spectrometry

Background:

• Electrochemical reactions generate transient intermediates and products that are challenging to characterize.
• On-line coupling of electrochemical techniques with mass spectrometry offers a powerful approach for real-time analysis.

Purpose of the Study:

• To develop and validate a three-electrode electrochemical cell coupled to an electrospray mass spectrometer for on-line electrochemical reaction studies.
• To investigate the reaction mechanisms and identify products of diphenyl sulfide oxidation, 9,10-diphenylanthracene pyridation, and nitrobenzene reduction.

Main Methods:

• On-line linear sweep voltammetry coupled with electrospray mass spectrometry (LSV-ES-MS).
• Utilized a three-electrode electrochemical cell integrated with an ES mass spectrometer.
• Analyzed ion abundance versus potential profiles to determine molecular weight and structural information.

Main Results:

• Successfully identified intermediates and products from the anodic oxidation of diphenyl sulfide, including diphenyl sulfoxide and pseudodimer sulfonium ion.
• Provided evidence supporting proposed mechanisms for pseudodimer sulfonium ion generation and pyridine addition to 9,10-diphenylanthracene radical cation.
• Discovered a new reaction product, [DPA(py) - H](+), from the pyridation of 9,10-diphenylanthracene.
• Detected intermediates and products of nitrobenzene reduction in both positive and negative electrospray ionization modes, overcoming inherent oxidation tendencies of ES.

Conclusions:

• The developed LSV-ES-MS system is effective for on-line characterization of electrochemical reaction intermediates and products.
• The technique provides valuable molecular weight and structural insights, aiding in the elucidation of reaction mechanisms.
• The method demonstrates versatility in analyzing both oxidation and reduction processes across various media.