DEMS
comparison

Convenience

The Spectro Inlets EC-MS is made by electrochemists for electrochemists, with the focus on making quantitative mass spectrometry measurements of reaction products easily accessible for electrochemists. DEMS systems are most often home-made and require vast time and money resources while not guaranteeing reproducibility, accuracy, and denying the possibility of quantitative measurements.

Sensitivity

The Spectro Inlets EC-MS enables sub-turnover resolution for gaseous analytes with 100% collection efficiency, together with full and fast control of dissolved gases at the working electrode. In conventional DEMS, the flux of molecules entering the MS is too large, thus a differential pumping system is needed. In the differential pumping stage, a large fraction of the molecules to be analyzed is lost. Due to the loss of molecules, sensitivity is dramatically reduced, and quantification of the signal becomes impossible.

Reproducibility

Our membrane chip technology is exactly defined by the accurate microfabrication process, whereas typical porous Teflon DEMS membranes exhibit immense variability by nature. As a result, the Spectro Inlets EC-MS offers maximum reproducibility.

Safety

The Spectro Inlets membrane microchip is designed to protect the mass spectrometer from inadvertent vacuum failures. On the contrary, DEMS membranes are susceptible to failure, are challenging to exchange, and exchange often results in irreproducible results.

Electrolyte saturation

The Spectro Inlets EC-MS cell is designed to provide rapid and facile electrolyte saturation. In DEMS, saturation of the electrolyte is impractical, slow, and necessitates extra equipment such as an external electrolyte reservoir, a bubbler, and a pump.

Quantification

The stagnant thin-layer EC-cell and the absence of differential pumping allow for 100% collection efficiency of the reaction products and make it possible to quantify submonolayer concentrations. The high-water evaporation rate in differentially pumped DEMS necessitates operation in flow mode, whereby most of the reaction products are lost in the flow, and another large fraction is lost to differential pumping.

Software

The Spectro Inlets EC-MS comes with a tailored software (Zilien), made to fully exploit the unique EC-MS system features with a user-friendly interface. On the contrary, with a DIY DEMS system, considerable effort must be made to combine and synchronize electrochemical and mass spectrometry datasets, to control active system components such as valves, and to run the mass spectrometer.

Time resolution

The Spectro Inlets EC-MS provides a fully defined geometry for transporting reaction products to the mass spectrometer. Time resolution in DEMS is obtained at the expense of collection efficiency, whereas the Spectro Inlets EC-MS locks both parameters with no compromise and full accuracy.

As a result, with DEMS it is impossible to measure small product amounts with decent time resolution, whereas EC-MS is specifically built to allow submonolayer sensitivity with subsecond time resolution.

Standardized sample holder

The Spectro Inlets EC-MS sample holder mounts standard 5 mm rotating disk electrodes (RDE) available off-the-shelf by PINE research instruments – PINE research instruments. Besides, it allows to use any type and size of counter and reference electrodes. In DEMS, the choice of working, counter, and reference electrodes is dependent on the cell geometry and often requires expensive manufactured electrodes to be custom-manufactured.

Dynamic range

The Spectro Inlets EC-MS enables resolving concentrations of any volatile dissolved species from saturation concentration to 6 orders of magnitude (one millionth) less than that.

DEMS is not optimized for anything, it barely represents an interface between a mass spectrometer and an electrochemical cell, sacrificing signal-to-noise and signal-to-background to make it happen.

Different types of classical DEMS inlets.
Mass Spectrom. Rev. 34, 64–92 (2015).
Schematic representation of the unique Spectro Inlets EC-MS microchip-based inlet
Schematic representation of the unique Spectro Inlets
EC-MS microchip-based inlet.
Schematic representation of the unique Spectro Inlets EC-MS microchip-based inlet
Schematic diagrams showing transport of an analyte i at two types of liquid – vacuum inlet systems – DOI
Schematic representation of the unique Spectro Inlets EC-MS microchip-based inlet
Chip-based vs differentially pumped EC-MS.
Model comparison of chip-based and differentially pumped electrochemistry – mass spectrometry in a flow system at steady state – DOI
Schematic representation of the unique Spectro Inlets EC-MS microchip-based inlet
Schematic representation of the unique Spectro Inlets EC-MS microchip-based inlet