An electrochemical cell for on-line electrochemistry mass spectrometry

A new electrochemical flow-through cell has been developed for on-line electrochemistry/mass spectrometry (EC/MS) that allows easy access to the working electrode for resurfacing or replacement and that can withstand back pressures of similar to 2000 psi. Simple off-line hydrodynamic electrochemical methods have been developed to determine the cell conversion efficiency. The methods can be used to determine the number of moles of analyte transferred from the cell to the LC/MS interface and thereby estimate the sensitivity in on-line EC/MS. The results that have been obtained show that the mobile-phase composition may influence the cell conversion efficiency. The highest conversion efficiency in the flow-through cell(similar to 32%) was obtained using 90/10 CH3OH/H2O as the mobile phase, while the lowest conversion efficiency (similar to 1.8%) was observed with an aqueous mobile phase. Using different mobile phases, the electrochemical now-through cell was tested in thermospray and particle beam (PB) EC/LC/MS. Conversion efficiencies obtained with the cell on-line in EC/PB/MS are in agreement with the efficiency determined by off-line hydrodynamic electrochemical methods. New insights into nucleophilic reactions of a quinone formed in the electrochemical oxidation of dopamine were obtained online by EC/PB/MS using the new cell.