pH is a measure of the concentration of hydrogen ions in a solution, with solutions below pH 7 being acidic and above pH 7 being basic. There are several methods to measure pH, including using indicators that change color depending on the pH level, hydrogen electrodes that apply a charge to solutions saturated with hydrogen gas to determine pH based on potential, and glass electrodes that measure the voltage between a glass and reference electrode immersed in the solution. Modern pH sensors using ion-sensitive field effect transistors are resistant to damage and can miniaturize measurements for small volumes and surfaces. pH is important to monitor in various industries such as pharmaceutical, chemical, food production, agriculture, and environmental applications.

2. pH is a measure of the hydorgen ion
concentration of a solution.
pH= -log[H+] concentration
Solutions with a pH
less than 7 are acidic
and solutions with a
pH greater than 7 are
basic.

3. 1) Measuring pH Using an Indicator
• involves comparing the standard color
corresponding to a known pH with the color of an indicator
immersed in the test liquid using buffer solution.
• preparing pH test paper which is soaked in the
indicator, then immersing the paper in the test liquid and
comparing its color with the standard color.

4. (2) Hydrogen-Electrode Method
A hydrogen electrode is
made by adding platinum black to
platinum wire or a platinum plate. It is
immersed in the test solution and an
electric charge is applied to the solution
and the solution is saturated with
hydrogen gas. The electrode potential is
measured between platinum black
electrode and silver chloride electrode.
This potential is inversely proportional to
pH of the solution.

5. (5) Glass-Electrode Method
The glass electrode method uses two
electrodes, a glass electrode and reference electrode,
to determine the pH of a solution by measuring the
voltage (potential) between them.

6. (6)Semiconductor sensor methods
This sensor, known as an ion sensitive field
effect transistor (ISFET), is not only resistant to damage but
also easily miniaturized. Miniaturization allows the use of
smaller amounts of sample for measurement, and makes it
possible to perform measurements in very small spaces and
on solid state surfaces.

7. •Pharmaceutical and chemical industry
•Quality control
•Controlling of chemical reactions
•Food production
•Quality control at dairies
•Quality control and efficient production in bakeries
•: agriculture, wastewater treatment, industrial processes,
environmental monitoring, and in research and development.