Interference
Because of the high adsorption activity of the platinized platinum electrode, it's very important to protect electrode surface and solution from the presence of organic substances as well as from atmospheric oxygen. Inorganic ions that can reduce to a lower valency state at the electrode also have to be avoided (e.g., Fe3+, CrO42-). A number of organic substances are also reduced by hydrogen at a platinum surface, and these also have to be avoided.
Cations that can reduce and deposit on the platinum can be source of interference: silver, mercury, copper, lead, cadmium and thallium.
Substances that can inactivate ("poison") the catalytic sites include arsenic, sulfides and other sulfur compounds, colloidal substances, alkaloids, and material found in living systems.
Read more about this topic: Standard Hydrogen Electrode
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