About ions : Characteristics of ion electrode

1. Fast, convenient and continuous measurement is possible.

Ion electrodes are used in a wide variety of fields, including wastewater measurement, monitoring of environmental pollution, and continuous concentration control at factories, as well as their quick and convenient characteristics and ability to measure continuously.

2. An abundant selection of measurement electrodes for anion analysis that other analysis instruments are not suited for.

Atomic absorption spectrometers, spectrophotometers, and other analytical instruments are also often used for metal ion analysis, making anion analysis unsuitable. Ion electrodes include many anion measuring electrodes such as halogen, nitric acid, and cyanide, which can be measured with simple operation.

3. Only specific ions are selectively measured.

For example, the fluoride ion electrode is sensitive only to free (F-) and is not measured for complexes.

4. The ion electrodes measure activity of ions.

The electromotive force generated at the ion electrode is proportional to the logarithm of the ion activity and is not a concentration. In order to determine the concentration, we have prepared a calibration curve for the electromotive force vs. concentration using a known standard solution, and measure the electromotive force of the unknown concentration solution to obtain the concentration from the calibration curve. In this case, the ionic strength must be considered. Generally, when the ionic strength increases, the activity of ions decreases even at the same concentration of ions. This means that if the ionic strength of the ionic standard solution is different from that of the test solution, an error will occur. In addition, if the ionic strength is different, the calibration curve will move. To prevent this, the ionic strength of the standard solution and the test solution must be constant, and an ionic strength modifier (ISA: salt of a strong electrolyte unrelated to ion measurement) is added. If the ion intensity becomes constant, the activity coefficient of the measurement solution becomes equal, and the ion concentration is proportional to the activity, which is proportional to the electromotive force generated by the ion electrode, and the correct ion concentration is obtained.