ELECTROCHEMISTRY COMBINED ONLINE WITH ELECTROSPRAY MASS-SPECTROMETRY

In this paper a variety of methods to couple electrochemistry on-line with electrospray mass spectrometry (EC/ES-MS) are presented, and the fundamental and analytical utility of this hybrid technique is illustr ated. The major problems encountered in coupling EC and ES-MS are disc ussed, and means to overcome them are presented. Three types of electr ochemical now cells, viz., a thin-layer electrode now-by cell, a tubul ar electrode now-through cell, and a porous electrode now-through cell , are discussed in regard to their suitability for this coupling, Meth ods for coupling each of these electrochemical cells on-line with ES-M S, either floated at or decoupled from the ES high voltage and control led by a constant current supply, a constant potential supply, or a po tentiostat are presented. Three applications are used to illustrate th e utility and versatility of the EC/ES-MS combination: (1) the ionizat ion of neutral analytes (i.e., perylene) for detection by ES-MS, (2) t he study of the products of electrode reactions (i.e., nickel(II) octa ethylporphyrin oxidation products), including relatively short-lived p roducts (i.e., beta-carotene oxidation products), and (3) the enhanced determination of metals (i,e., elemental silver) achieved by coupling anodic stripping voltammetry online with ES-MS.