title: Mass spectrometric methods for monitoring redox processes in electrochemical cells.
abstract: Electrochemistry (EC) is a mature scientific discipline aimed to study the movement of electrons in an oxidation-reduction reaction. EC covers techniques that use a measurement of potential, charge, or current to determine the concentration or the chemical reactivity of analytes. The electrical signal is directly converted into chemical information. For in-depth characterization of complex electrochemical reactions involving the formation of diverse intermediates, products and byproducts, EC is usually combined with other analytical techniques, and particularly the hyphenation of EC with mass spectrometry (MS) has found broad applicability. The analysis of gases and volatile intermediates and products formed at electrode surfaces is enabled by differential electrochemical mass spectrometry (DEMS). In DEMS an electrochemical cell is sampled with a membrane interface for electron ionization (EI)-MS. The chemical space amenable to EC/MS (i.e., bioorganic molecules including proteins, peptides, nucleic acids, and drugs) was significantly increased by employing electrospray ionization (ESI)-MS. In the simplest setup, the EC of the ESI process is used to analytical advantage. A limitation of this approach is, however, its inability to precisely control the electrochemical potential at the emitter electrode. Thus, particularly for studying mechanistic aspects of electrochemical processes, the hyphenation of discrete electrochemical cells with ESI-MS was found to be more appropriate. The analytical power of EC/ESI-MS can further be increased by integrating liquid chromatography (LC) as an additional dimension of separation. Chromatographic separation was found to be particularly useful to reduce the complexity of the sample submitted either to the EC cell or to ESI-MS. Thus, both EC/LC/ESI-MS and LC/EC/ESI-MS are common.
authors: Institute of Legal Medicine and Core Facility Metabolomics, Innsbruck Medical University, Innsbruck, Austria.
authors: Herbert
authors: H
authors: Oberacher
authors: Florian
authors: F
authors: Pitterl
authors: Robert
authors: R
authors: Erb
authors: Sabine
authors: S
authors: Plattner
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D013058:Mass Spectrometry / Q000379:methods*; D055432:Metabolomics / Q000379:methods; D010084:Oxidation-Reduction; D004364:Pharmaceutical Preparations / Q000378:metabolism; D011506:Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods
chemical_list: D004364:Pharmaceutical Preparations; D011506:Proteins
keywords: differential electrochemical mass spectrometry; electrochemistry; electron ionization; electrospray ionization; liquid chromatography; mass spectrometry