Friday, November 22, 2019

Determination of pH using glass electrode

The pH is the measure of the hydrogen ion concentration in a sample solution. It expresses the degree of acidity or basicity (alkalinity) of a solution. There are different methods to determine pH paper or indicator paper, litmus paper (Blue, Red), and indicators, etc. However, a pH meter is one of the most accurate types of measurement and is widely used to determine the pH value in the pH scale ranges from 0 to 14.
The pH can be determined more accurately with a pH meter that includes a probe, an electrode, and a display. A variety of pH electrodes are available in which glass electrodes are commonly used. Various glass electrodes are also available in the market. Each glass electrode has special properties so they must be carefully selected to suit the measurement application. Because the process of taking the pH measurement changes the glass membrane of a pH glass electrode over time. Due to exposure to water, alkali ions dissolve from the glass surface and the oxide groups of silicates become OH groups that cause a source layer. The use of a special pH glass electrode membrane is a reproducible equilibrium between the solution and the glass surface, dependent only on the hydrogen ion concentration in the solution and source layer.
In the glass electrode method of pH determination, the recognized pH of a reference solution is measured by two electrodes, a glass electrode, and a reference electrode, and determining the voltage generated amongst these electrodes. The variation in pH between the solution outside and inside the membrane generates an electromotive force proportional to this pH difference.

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