Gas Phase Electrochemical Analysis of Amino Acids and their Fragments

All chemical reactions involve electron rearrangement within or between molecules. The changes are best studied by methods such as electrochemistry, but these have been developed mainly for liquids and solids rather than gases. This exclusion limits our understanding of electron transfer processes that are central in plasma systems, which are of high scientific, industrial, and environmental importance. Here we describe electrochemical measurements in the gas phase of small organic molecules contained in flame plasma, by probing the redox activity of the resulting chemical fragments using cyclic voltammetry. Unique current-voltage spectra are recorded for eight amino acids and their fragments, through specific electron transfer reactions at the solid/gas interface. We identify and assign Faradaic peaks in the current-voltage spectra to the fragments using stable analogues of the fragments and in situ mass spectroscopy. We show that this approach provides unambiguous identification of organic based molecules, with a sensitivity and power of speciation to rival mass spectrometry.