Technology

Standardized sample holder

Electrode assembly, with a disk contact core assembly from Pine Research used to retain the working electrode in the EC cell.

Mounting of cell onto membrane chip

Cross sectional view of the assembled flow cell.

Photographs of the EC cell equipped with a B 3420+ Ag/AgCl electrode, a coiled Pt wire as counter electrode, and a gas-tight syringe to inject electrolyte in the cell.

The Spectro Inlets EC-MS system is provided with a tailored electrochemistry cell. We developed the cell in collaboration with Pine Research Instruments and made it compatible with their standard 5 mm cylindrical electrodes used for RDE measurements. Most metals and glassy carbon supports are readily available off the shelf in this common electrode format, so the user does not need to waste time and money manufacturing custom electrodes. Our EC-cell is manufactured in PCTFE to make it chemically inert and cleanable even with the harshest methods, e.g. piranha solution. The cell is equipped with four threaded openings: two for the reference and the counter electrodes, and two for electrolyte inlet and outlet IDEX™ microfluidic fittings can be mounted. The thickness of the electrolyte layer is constrained to be precisely 100 µm, providing a well-defined geometry yielding a well-defined mass transport to and from the electrode, excellent time-response, and 100 % collection efficiency for volatile electrochemical reaction products. The cell is coupled to glass cylinders made with a conical ground glass joint, a glass frit and a Luer connector at the bottom to connect a reference and a counter electrode. Such glass connectors are designed to perfectly fit e.g. an Ag/AgCl reference electrode B 3420+ from SI analytics. Any other reference electrode can be used as well.

Mounting and removal of the EC cell can be carried out in seconds, and the same is true for working electrode exchange. This allows users to maximize productivity as several experiments can be performed in a very short time. For example, a full activity volcano plot can be measured within one day.

Because of the extraordinary control of experimental parameters obtained by microchip design, the transport mechanisms of species from the electrode surface through the electrolyte and to the sampling volume are fully defined and modelled (Trimarco et al. Electrochim. Acta). The thin-layer cell is designed so that all volatile molecules that are evolved at the electrode surface are transferred to the mass spectrometer and thereby quantified. This is a truly unique characteristic of the Spectro Inlets system and it allows to obtain e.g. the data shown in.

The cell can also be operated in flow mode.