Use of a porous electrode for in situ mass spectrometric determination of volatile electrode reaction products

Abstract

The interpretation of the origin of products isolated after a bulk electrolysis is frequently subject to the problems caused by chemical reactions occurring between electrode intermediates and other species present in solution. In such situations, it is ordinarily considered desirable to identify an electrode intermediate as soon as possible after its production at the elec-

Differential electrochemical mass spectrometry

“…Mass spectrometry was one of the first spectroscopic techniques, the potential of which was elucidated in this aspect. This was started by Bruckenstein and Gadde [1] who collected gaseous electrochemical reaction products in a vacuum system before detecting them by mass spectrometry (using electron impact ionization). Later, Wolter and Heitbaum [2,3], still using a porous Teflon membrane covered by a 100 m lacquer of the electrocatalyst as the interface to the mass spectrometer, considerably improved the vacuum system so that the time constant became short enough to allow the on-line detection of volatile electrochemical reaction products, e.g., during cyclic voltammetry.…”

High Rate Detection of Volatile Products Using Differential Electrochemical Mass Spectrometry: Combining an Electrode-Coated Membrane with Hydrodynamic Flow in a Wall-Tube Configuration

“…This was originally accomplished by using a Teflon-coated frit to separate the aqueous phase of an electrochemical cell from the vacuum present within a mass spectrometer, thus allowing volatile gases to diffuse from the solution phase into the spectrometer for detection. 2 Subsequent improvements included the introduction of differential electrochemical mass spectrometry (DEMS), which substantially reduced detection time by connecting the electrochemical cell directly to the ionization chamber of the mass spectrometric system and thereby significantly increased the gas flux into the detector. 3 Coupled electrochemical mass spectrometric techniques have further been extended to detect nonvolatile products, 4 for use during the indirect detection of solid and single crystal electrodes, 5 for scanning detection near electrode surfaces, 6 combined with quartz crystal microbalance, 7 combined with infrared reflection measurements, 8 and in several configurations coupled to hydrodynamic electrolyte flow, as will be discussed below.…”

Uso de espectrometria de massas em medidas eletroquímicas - a técnica de DEMS

“…Embora algumas técnicas clássicas, como voltametria cíclica, nos permitam especular sobre a natureza das reações e dos produtos formados, estes métodos são indiretos 6 . Com o intuito de superar algumas destas limitações, Bruckenstein e Gadde 10 , no princípio dos anos 70, conectaram uma célula eletroquímica a um espectrômetro de massa usando um eletrodo poroso hidrofóbico como interface entre o alto vácuo no espectrômetro de massa e a pressão atmosféri-ca na cela eletroquímica; tornando possível a coleta dos produtos gasosos das reações eletroquímicas diretamente no sistema de entrada de um espectrômetro de massa usual. Tal técnica foi denominada de EMS (espectrometria de massas eletroquímica) e possibilitou uma melhor compreensão dos mecanismos reacionais.…”