Impact of Coexistent Ions

Although ion selective electrodes have good selectivity with respect to the ions to be measured, they may react to the other ions.
The ions which interfere with the measurement of the concentration of the ionsto be measured are called "interfering ion". Therefore, when using the ion electrode method, it is important to know the effects of coexistent ions and take measures to avoid them.

the impact that coexistent ions will have on electromotive force measurements with the ion electrode method can be predicted  from the extent to which they react with the structure meterial of the ion selective membrane. For example, in the case of solid membrane electrodes, coexistent ions that may form compounds with poor solubility or may form complex salts with the structure material of the ion selective membrane are likely to have a significant impact, whereas in the case of liquid membrane electrodes,  coexistent ions that may form an association with the components of the ion selective membrane are highly likely to have an impact.

the following table shows the impact of coexistent ions against each ion sensor cartridges.
Confirm the impact of coexistent ions and take measure to avoid them because the impact of coexistent ions varies depending on the composition of the sample solution.

Ion sensor cartridgeCoexistent ionSelection coefficient
NO3-ClO4-, I-, SCN-NO
NO2-, Br-1×10ー1
HCO3-, CH3CO2-6×10ー4
Ca2+Fe2+, Fe3+, Zn2+NO
K+, Na+1×10ー3
Na+K+, Cs+1×10-2
Li+, NH4+1×10-3
Sr2+, Ba2+3×10-3
Mg2+, Ca2+1×10ー4
Water & Liquid Corporate