Calibration of pH Meter

Calibrate pH meter daily with pH 4.01, 7.00 and 9.18 buffer solutions.

Preparation of Buffer Solutions

pH 4.01 at 25°C (Potassium Hydrogen Phthalate Buffer): Dissolve 10.21 g of Potassium hydrogen phthalate previously dried for 2 hours at 120°C ± 2°C, in purified water and make-up the volume to 1000 ml with purified water.
pH 7.00 at 25ºC: Take 1 capsule in 100 ml volumetric flask and dissolve with purified water. Make up to volume to 100 ml with purified water.
pH 9.18 at 25°C (Sodium Tetra borate Buffer): Dissolve 3.814 g of Sodium Tetra borate in purified water and make-up the volume to 1000 ml with purified water.
Prepare the buffer solution after every 07 days. If any changes observed in physical appearance, then prepare new buffer solution.
Note: Validity of pH 7.0 buffer solution is for one week.
General Instructions
Check the validity of the buffer solutions before use.
After calibration do not switch off the pH meter. If done, then again calibrate the pH meter before use.

Procedure for Calibration

Press the MEM CLEAR key, pH meter show 1) Calibration 2) Reading 3) All; select 3 for all memory clearance & then press enter.
Transfer approximately 50 ml of each buffer solution from stock buffer solution in 100 ml capacity dry beaker; dip the electrode in solution of pH buffer 7.00.
Then press CAL key, pH meter show 1) Standardization 2) Calibration; select 1 for standardization then press enter.
Standardize pH meter with 7.00 pH buffer, then after stable reading press enter.
Then screen show Calibration 1) Yes 2) No; press 1 for calibration.
Then immerse the electrode in the buffer solution of pH 4.01. Wait till the screen shows stable value.
Rinse the electrode with purified water and immerse in the standard buffer solution of pH 9.18 Wait till the screen shows stable value.
Now verify the pH of buffer solutions pH 4.01, 7.00, 9.18 and record the activity.
Verification of pH reading should be with in limit 0.05 of standard buffer.
After verification of pH, discard the used buffer.
Report any discrepancy observed during calibration of instrument to F&D In-Charge for corrective and preventive action.
F & D In-Charge informs the defect to Maintenance Department service engineer to rectify the defect. Meanwhile affix ‘Under Maintenance’ label on the instrument.
Calibration should be done after maintenance.

Precaution and Cleaning