pH meter principle and working

pH Meter Definition

A pH meter is an automatic measurement tool used to determine the pH of the liquid. A rough idea of pH is often achieved using indicators, pH papers, or litmus papers that change color and support the pH level. Such types have limits on their precision, and they are often difficult to interpret correctly. A pH meter consists of an electrode that's attached to an electronic meter that monitors and displays the right pH reading.

 

pH Measurement

Determining the pH of a solution is extremely essential and useful for several chemical and analytical tasks and its measurement determines any follow-up measurements.

Taking a pH measurement often seems to be trivial, which is that the reason why pH measurements are frequently not questioned. But to form a useful pH measurement close attention must be paid to the measurement's details. to form a correct pH measurement and avoid errors you want to first be conversant in the fundamentals of pH measurement.

·   If the H+ density is more than OH-, the substance is acidic; i.e., the pH amount is a smaller amount than 7.

·   If the OH- intensity is more than H+, the substance is basic, including a pH value above 7.

·   If identical quantities of H+ and OH- ions are present, the substance is neutral, with a pH of seven.

 

pH meter working principle

Using the Nernst equation, the electric potential is employed to measure the proton concentration indicating the pH of a given solution. Because of the electric potential between the 2 electrodes, the electron flows and generates a current. This generated current is measured by a voltmeter. the connection between the electric potential generated current and pH has been derived. The electric potential of 1 pH is 59.16mV at 25° C and hence when there's a difference of 1 pH unit, there'll be a change in voltage by 59.16mV. This relationship is used in measuring the pH.

 

Key parts of a pH meter

The Solution being examined.

·   The Glass electrode, consisting of,

·   A slim layer of silica glass including metal salts, inside which there's a potassium chloride solution.

·   An internal electrode

·   Constructed from silver/silver chloride.

·   Hydrogen ions produced within the experiment solution communicate with the outer surface of the glass.

·   Hydrogen ions produced within the potassium chloride solution communicate within the surface of the glass.

·   The meter regulates the variation in voltage between the 2 surfaces of the glass and turns this “potential difference” into a pH reading.

·   The reference electrode is a reference for the analysis.

 

Calibration of pH Meter

Calibration is required because the glass electrode doesn't provide reproducible electrostatic potentials across longer periods of your time.

 

·   First, confirm the right measurement mode is chosen within the pH meter.

·   Then wash the electrode with water and don’t wipe the electrodes, otherwise, it'll generate a charge on the electrodes.

·   All standards and samples are delivered to 25-degree centigrade before use.

·   Now immerse the electrodes within the quality solution or calibration solution (pH 7/pH 10). check that the endpoint of the electrodes is fully immersed within the solution. to make the homogenous sample stir the electrodes within the buffer.

·   Now set pH calibration mode by pressing the CAL/MEAS key. The CAL sign is going to be displayed.

·   The measured reading is going to be shown by the first display whereas the pH standard solution reading is displayed by the smaller secondary screen.

·   After stabilization of the pH value, confirm the calibration by pressing the HOLD/ENTER key.

·   Now the pH meter is calibrated to the present solution.

·   Finally, wash the electrodes with water and place them into the solution.

 

Procedure and operation of pH Meter

The pH meter should be calibrated with acceptable solutions like pH 07.00, 04.00, and 09.20 to verify the performance of the pH electrode before pH measurement. The method may look like a touch variation counting on the pH meter used and therefore the electrode used; however, in most cases the pH determination process is extremely similar.

·   Clean the electrode and temperature probe of the pH meter with deionized water and wipe gently with soft tissue.

·   Immerse the electrode within the sample solution.

·   Now press the pH mode key on the board.

·   The instrument will display the pH.

·   Note down the reading or simply print the reading if the printer is connected.

·   Reset the instrument and again clean the temperature probe and electrode of the pH meter with water and wipe gently with soft tissue.

 

Types of pH meters

The pH meter ranges from easy and economical pen-like apparatus with computer interfaces and complex and expensive laboratory apparatus, during which many inputs are recorded for indicators and temperature measurements to manage the variation in pH thanks to temperature. The display could also be digital and therefore the systems could also be operated by batteries or depend upon the electrical power.

There are special pH meters that will be utilized in particular applications that allow pH determination calorimetrically. Commercial pH meters are available supporting solid-state electrodes, rather than traditional glass electrodes.

 

Application of pH Meter

·   The basic application of the pH meter allows us to work out if any liquid sample is acidic or basic or neutral.

·   The pH is employed mainly within the pharmaceutical, beverage, chemical, and food industries.

·   It is commonly utilized in chemistry to work out the acidity or basicity of a substance.

·   It is utilized in production to make sure product quality.

·   The pH is widely utilized in the event and research in many fields.

·   The pH is extremely significant for checking the consistency of water, soil, and pesticides within the agricultural sector.

 

 

SUMMARY

The pH meter maybe a physics instrument but its working is chemistry oriented. The pH meter is an important part of the industry, Food Industry, Pharmaceutical Industry, and Agriculture sector. It allows us to understand the character of the solvent and thus provides insights to require further actions accordingly. If a product has a low pH value, then the chemist can raise its pH with some alkali solutions. However, the pH meter seems like a really simple instrument but its functionality puts it at the highest position of Chemo-physics instruments.