pH Meter Calibration: How to Perform

Table of contents

Calibration Description
- Reagents and instruments
- General
- Scope
- Responsibility
Frequency
Procedure
Buffer preparation

pH Meter Calibration Description

Note*:

Nowadays readymade-commercial buffer (with valid COA) are used for the calibration of pH meter
See the buffer preparation section of this post to prepare the same in the laboratory

General

For the smooth running of pH meter and to achieve precision, accuracy, and repeatability in analysis calibration of the pH meter is required.

Scope

The procedure applies to all pH meters of the company

Responsibility

Research Scientists/Chemists/Analysts responsible for the calibration of the instruments

HOD

To ensure the compliance of the SOP in the Analytical development laboratory or Quality control Laboratory (as applicable)

Daily

Follow the operational SOP for the operation of the instrument
Select the calibration mode
Select the Linear regression interpolation method from the calibration mode
Enter first value as 1.68 and enter
Dip the electrode and the temperature probe in pH 1.68 solution
Wait to stabilise the reading . Once the reading stabilise press enter
Remove the electrode from the pH 1.68 buffer and rinse it thoroughly with purified water
Soak the excess water with tissue paper
Insert the pH electrode and sensor in the beaker having a pH 4.01 solution
Repeat the above steps (1 to 9) for pH 4.01. pH 6.86, pH 9.18 and pH 12.45
Record the result in the calibration sheet
After completion of the above 5 points buffer pH checking calculate the slope
If the pH meter slope lies within the limit report of the value (of the buffer used and the slope obtained)

Acceptance Criteria: 90 to 105%

Tolerance: ± 0.05 Standard pH buffer

pH 1.68: Weigh accurately about 1.271 gm of potassium tetraoxalate and transfer it to 100 ml volumetric flask and make the volume with water. Sonicate to dissolve
pH 4.01: Weigh accurately about 1.021 gm of Potassium phthalate and transfer to 100 ml of volumetric flask and make the volume with water, Sonicate to dissolve
pH 6.86: Weigh accurately about 348 mg of Potassium dihydrogen phosphate and 355 mg of anhydrous Disodium Hydrogen phosphate and transfer to 100 ml of volumetric flask and make the volume with water, Sonicate to dissolve
pH 9.18: Weigh accurately about 381.4 mg of Sodium tetraborate and transfer to 100 ml of volumetric flask and make the volume with water, Sonicate to dissolve
pH 12.45: Prepare saturated solution of Calcium hydroxide in water (Shake excess of Calcium hydroxide and decant before use)

You may also want to check out other articles on my blog, such as:

pH meter calibration is performed using buffer 1.68, 4.01. pH 6.86, pH 9.18 and pH 12.45

Daily