horiba 6582S-10C, Instruction Manual

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61
Reference
 Impact of pH
The usable pH range is determined depending on the type and the
structure of the ion selective electrode.
In general, this range is smaller when the concentration of the ions to be
measured is lower.
Also, depending on the ion selective electrodes, the components of the ion
selective membrane may be dissolved by the pH or the electrode potential
may change due to the impact of the pH.
Furthermore, the impact of pH may cause a decrease in the slope of the ion
selective electrode, or parallel shifting of the calibration curve.
To prevent these effects, set the pH to an appropriate value in advance and
keep it constant.
One simple method to set the pH of the sample solution to an appropriate
value for measurement is to prepare a pH buffer solution (not containing
interfering ions) that will not interfere with the ion selective electrode in
advance, and add a small amount of it to the sample solution.

How to prepare a sample solution
If the pH of the sample solution is below 5 or more than 11, adjust the pH as
described in the following procedure.

If the pH of the sample solution exceeds 11, adjust the pH in the range of
5 to 11 by adding hydrochloric acid.

If the pH of the sample solution is less than 5, adjust the pH in the range
of 5 to 11 by adding sodium hydroxide.