Solid Electrodes
Schematic diagram showing a solid electrode. The electrode is fashioned into a disk and sealed in the end of an inert polymer support along with an electrical lead.
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Potential Windows for Hg, Pt, and C Electrodes
The approximate potential windows for mercury, platinum, and carbon (graphite) electrodes in acidic, neutral, and basic aqueous solvents are shown here. The useful potential windows are displayed in green; potentials in red […]
Mercury Electrodes
Three examples of mercury electrodes are illustrated here: (a) hanging mercury drop electrode, or HMDE; (b) dropping mercury electrode, or DME; and (c) static mercury drop electrode, or SMDE. In the hanging […]
External Generation of Oxidizing Agents or Reducing Agents
Shown here is one example of a device for the external generation of oxidizing agents and reducing agents for controlled-current coulometry. A solution containing the mediator flows into a small-volume electrochemical cell. […]
Controlled-Current Coulometry
A second approach to coulometry is to use a constant current in place of a constant potential, which produces the current–time profile shown here. Controlled-current coulometry has two advantages over controlled-potential coulometry. […]
Controlled-Potential Coulometry
Coulometry is based on an exhaustive electrolysis of the analyte. By exhaustive we mean that the analyte is completely oxidized or reduced at the working electrode or that it reacts completely with […]
Disposable ISE
Schematic diagram of a disposable ion-selective electrode created by screen-printing. In (a) a thin film of conducting silver is printed on a polyester substrate and a film of Ag2S overlaid near the […]
Activity vs. Concentration
The photo below provides a demonstration of the difference between activity and concentration using the indicator methyl green. The indicator is yellow in its acid form (beaker a: 1.0 M HCl) and […]
Enzyme Electrode
A gas-sensing electrode can be modified to create a potentiometric electrode that respond to a biochemically important species, such as enzymes. One example of an enzyme electrode is the urea electrode, which is […]
Gas-Sensing Membrane Electrode
A number of membrane electrodes respond to the concentration of a dissolved gas. The basic design of a gas-sensing electrode consists of a thin membrane that separates the sample from an inner […]
Liquid Membrane Ion-Selective Electrode
Another class of ion-selective electrodes uses a hydrophobic membrane containing a liquid organic complexing agent that reacts selectively with the analyte. Three types of organic complexing agents have been used: cation exchangers, […]
Solid-State Ion-Selective Electrode
Schematic diagram of a solid-state electrode, the membrane for which is either a polycrystalline inorganic salt or a single crystal of an inorganic salt. We can fashion a polycrystalline solid-state ion-selective electrode […]