Measurement of sample including solvent other than water.
In the sample including non-aqueous solvent, the pH value indicated on the pH meter is not simple to use such as that in the aqueous solution. For this reason, note that the pH value measured in the non-aqueous solvent is only an indicator which shows the amount of hydrogen ion activity in the measuring solvent.
When performing a measurement, exercise the caution regarding the following items.
<Precautions>
- Use the glass electrode, the reference electrode (double-junction type) and the temperature compensation electrode.
- Because it takes a long time until the indication value becomes stable, it is advisable to read it approximately in 5 minutes.
- For more accurate measurement, immerse the sensing part of the glass electrode in sample than all day and night before the measurement.
- After the measurement, immerse the sensing part of the glass electrode in 0.1 mol/L HCl for around 10 minutes, and then rinse it sufficiently with pure water.
- Also, rinse the inside of the external cylinder of the reference sufficiently with pure water.
- If the pH value is not within the range from pH 0 to pH 14, switch the display of the pH meter unit to mV display mode, and then perform the measurement.
The KCl that leaks from the liquid junction of the reference electrode with the inner solution (KCl solution) does not in general dissolve in most non-aqueous solutions, so that the liquid junction becomes obstructed. (In order to solve this problem, some electrodes utilize lithium acetate (CH3COOLi), which is soluble in organic solvent, as the inner solvent on the outer side of a double-junction construction.)
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