A ROLE FOR ELECTROSPRAY MASS-SPECTROMETRY IN ELECTROCHEMICAL STUDIES

The advantages of coupling bulk electrolysis with electrospray mass spectrometry (ESMS) are demonstrated using the oxidative electrolyses of copper, nickel, and cobalt diethyldithiocarbamates (Cu(Et(2)dtc)(2), Ni(Et(2)dtc)(2), and Co(Et(2)dtc)(3)). Both on-line and off-line methods have been developed to detect the charged species formed in the oxidation processes ([Cu(Et(2)dtc)(2)](+), [Ni(Et(2)dtc)(3)](+), and [Co-2(Et(2)dtc)(5)](+), respectively) using common electrochemical solvents and electrolyte (acetonitrile, dichloromethane, and tetrabutylammonium hexafluorophosphate (BU4NPF6)). In the off-line mode, conditions are established for electrolyses of solutions containing equimolar (2 mM) electroactive compound and electrolyte. Following dilution, an excellent signal-to-noise ratio is obtained for the ES mass spectrum of the electrolysis product. On-line electrolysis with ESMS detection of charged solution-soluble products is achieved using a simple now cell constructed from two lengths of Pt microtubing. The outlet of the cell is connected directly to the fused silica capillary of the spectrometer, and after electrolysis of an acetonitrile solution containing 0.2 mM electroactive compound and 0.2 mM Bu(4)NPF(6), the product is detected with high sensitivity. The methods should be readily applied to most other common electrochemical solvents and electrolytes.