Learn the principle, types, and procedure of pH meter which is used to measure hydrogen-ion activity (acidity or alkalinity) in solution.
What is a pH meter?
A pH meter is an automated measurement tool used to determine the pH of the liquid. It is also known as a potentiometric pH meter since it determines the difference in electrical potential between a pH electrode and a reference electrode.
A rough idea of pH can be achieved using indicators, pH papers, or litmus papers that change color based on the pH level. Such types have limits on their precision, and it can be difficult to interpret correctly. Hence a pH meter is broadly used to determine the exact pH of the sample solution.
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A pH meter consists of an electrode that is attached to an electronic meter that monitors and displays the correct pH reading. A glass electrode made of a specialized glass membrane is sealed at the end to forming a bulb. An internal standard acidity solution, generally 0.1 M hydrochloric acid (HCl), and an internal reference electrode, REin (often an Ag/AgCl wire electrode), are included within the glass. This solution is referred to as the reference solution, which has a pH of 07.00.
A second electrode, REext, is inserted into potassium chloride (KCl)-soaked external tube. Around the first enclosed glass tube containing the 0.1 M HCl, this external tube forms a concentric enclosure. This setup is known as a combination pH electrode.
Working principle of pH meter:
It detects the difference in voltage between the two electrodes i.e. glass electrode and reference electrode. When both electrodes are present, the electrode is referred to as a combination electrode, and it is placed into the solution to be tested.
These two electrodes are immersed in a solution, and after that, the H+ ions in the test solution exchange for other positively charged ions present on the glass ball. So there is an action between these plus ions of the solution and the H+ ions or positively charged ions present on the glass bulb.
The difference in electric potential between the two electrodes is detected by the amplifier. The pH unit is the difference between these potentials. The difference in electric potential between the two electrodes is detected by the amplifier. The difference of this potential is known as the pH unit.
Types of pH meter:
The pH meter ranges from easy and economical pen-like apparatus with computer interfaces and complex and costly laboratory apparatus, in which many inputs are recorded for indicators and temperature measurements to manage the variation in pH due to temperature. The display may be digital and the systems may be operated by batteries or depend on the electric power.
There are special pH meters that can be used in particular applications that allow pH determination colorimetrically. Commercial pH meters are available based on solid-state electrodes, instead of traditional glass electrodes.
Procedure of pH meter:
Before beginning a pH meter process, we must recognize the various parts essential to perform the process. A pH meter consists of three major parts such as pH electrode or glass electrode or combined electrode, a temperature probe, and electronic control unit.
pH Electrode:
Glass electrodes are the most widely used pH electrodes made of special glass. Silver/silver chloride (Ag / AgCl) is the most regular reference electrode form used today.
Temperature probe:
For accurate determination of pH, some pH meters automatically compensate for temperature. This is achieved by a meter, temperature probe, which, along with the electrode, is submerged in the sample solution.
Electronic control unit:
To produce a chemical signal, the electrode responds to the concentration of hydrogen ions in the sample solution. This signal is then transformed into pH values shown on the screen.
- The pH meter should be calibrated with the appropriate buffer solution such as pH 07.00, 04.00, and 09.20 to confirm the performance of the pH electrode before pH measurement. The process may look a little variation depending on the pH meter used and the electrode used however in most cases the pH determination process is very similar.
- Clean the electrode and temperature probe with deionized water and wipe gently with soft tissue paper.
- Immerse the electrode in the sample solution.
- Press the pH mode key which is on the board.
- The instrument will display the pH.
- Save the reading or print the reading if the printer is connected.
- Reset the instrument and again clean the electrode and temperature probe with distilled water and wipe gently with soft tissue paper.
Applications of pH meter:
- The basic application of the pH meter allows us to determine if any liquid sample is acidic or basic or neutral.
- The pH is used mainly in the pharmaceutical, beverage, chemical, and food industries.
- It is commonly used in chemistry to determine the acidity or basicity of a substance.
- It is used in production to ensure product quality.
- The pH is widely used in the development and research in many fields.
- The pH is very significant for checking the consistency of water, soil, and pesticides in the agricultural sector.
- The pH meter is an improved version for pH determination than traditional methods, providing simple, accurate pH.
Advantages of pH meter:
- This makes pH measurement quick and simple.
- The advantage of the pH meter is that they are compact and portable (Pen pH meter) you can use at a different location.
- It can be used for a wide variety of applications.
- This indicator gives an accurate pH value compared to pH paper, and indicators.
- It covers the entire range of pH i.e. 01 to 14.
- With a standard buffer solution, you can calibrate the pH meter to improve consistency.
Disadvantages of pH meter:
- Deposition on the electrode membrane can cause an error in the results.
- Because of fragile glass electrodes, there is a risk of breakage.
- It is often necessary to calibrate the pH meter.
- To calibrate the pH meter you need buffer solutions that make it expensive.
FAQ (Frequently Asked Questions):
What is pH meter?
A pH meter is an apparatus used to determine the acidity or alkalinity of a solution. The pH is a measure of hydrogen ion concentration.
What is the basic principle pH meter?
A pH meter gives information for how acidic or alkaline a solution is. Measuring the concentration of hydrogen ions in the basic principle of the pH meter.
Why do you need to calibrate a pH meter?
To prevent drift and maintain the accuracy of the pH meter, it is necessary to periodically calibrate the pH.
Why are buffer solutions used to calibrate the pH meter?
The buffer solutions are used to calibrate a pH meter as they avoid changes in pH. You can adjust the value of pH by using the standard buffer solution of known pH.
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