| Metrohm® Electrolytes and storage
solutions
Trust Metrohm electrolytes and storage solutions to protect and increase the lifetime
of your electrodes.
Selecting your electrode filling solution
In order to achieve a high degree of measuring accuracy, the filling solution or electrolyte
must be selected so that any diffusion potentials formed are negligible; this is to a large extent
achieved by the use of c(KCl) = 3 mol/L. On the one hand, the ionic motilities of K+ and
Cl- are practically the same; on the other hand, the ionic concentration in the sample
solution is negligible in comparison to c(KCl) = 3 mol/L. This is why KCl electrolyte is standard
in all combined Metrohm electrodes and reference electrodes. However, certain media require the use
of other electrolyte compositions in order to suppress effects that occur in addition to the diffusion
potential.
| Sample solution |
Problem with c(KCl) = 3 mol/L |
Alternative electrolyte |
| Silver ions |
Precipitation of AgCl, slow response |
KNO3 saturated |
| Nonaqueous |
Precipitation of KCl solutions and electrolyte immiscible, unsteady signal |
2 mol/L LiCl in ethanol or LiCl saturated in ethanol |
| Proteins/polypeptides |
Precipitation of the proteins with KCl and AgCl, zero point shift/reduced slope |
Idrolyte1 |
| Semi-solid substances |
Contamination of diaphragm, zero point shift/slow response |
Solid electrolyte in combination with pinhole diaphragm |
| Surfactants (proteins) |
Adsorption on diaphragm, zero point shift/reduced slope |
Porolyte2 |
1. Idrolyte is a glycerol-based electrolyte whose chloride ion activity corresponds
to that of a KCl solution with c(KCl) = 3 mol/L.
2. Porolyte is a KCl solution that has been gelled by polymerization, and it is used in the Porotrode®
electrode with a capillary diaphragm. |
