1. OBJECTIVE
To lay down the procedure for operation, Cleaning and Calibration of pH Meter
2. SCOPE
This procedure is applicable to Quality Control Department
3. RESPONSIBILITY
• Officer QC
• Manager QC
4. SAFETY INSTRUCTIONS
• Handle the strong acid and base carefully used in rejuvenation.
• Proper handling the instrument.
• Temperature should be carefully adjusted and maintained
5. PROCEDURE
5.1 OPERATION
5.1.1 Press “ON” to switch on the pH meter.
5.1.2 Rinse the electrode with de-ionized or distilled water before use to remove any impurities adhering to the probe body.
5.1.3 Maintain the temperature of the sample 25 °C ± 2 °C, unless otherwise specified in the individual monograph and dip the electrode along with the temperature sensor in to the sample.
5.1.4 When dipping the electrode into the sample, the sensor or the glass bulb of the electrode must be completely immersed into the sample, Stir the probe gently in the sample to create the homogeneous sample.
5.1.5 Allow time for the reading to stabilize.
5.1.6 Record the observed value of pH and temperature in the respective test data sheet or operational log book of pH meter.
5.1.7 Wash the electrode in the de-ionized water after use and store the electrode in the storage solution or pH buffer 5.0 or 7.0.
5.2 STORAGE OF ELECTRODE
5.2.1 Always keep the electrode bulb wet, preferably in the pH 5.00 to 5.01 buffers.
5.2.2 Raw water is also acceptable storage media, but avoid storage in de-ionized water
5.2.3 During handling of pH meter, check if electrode is broken; replace the same with new electrode.
5.2.4 Rejuvenation
5.2.4.1 If the electrode is fail to give appropriate result during calibration, the same shall be rejuvenated as mention below:
5.2.4.1.1 Dip and stir the electrode in ethyl alcohol for five minutes.
5.2.4.1.2 Leave the electrode in the tap water for 15 minutes.
5.2.4.1.3 Dip and stir the electrode in concentrated acid (e.gHCl, H2SO4) for five minutes.
5.2.4.1.4 Leave the electrode in the Tap water for 15 minutes.
5.2.4.1.5 Dip and stir the electrode in strong base (e.gNaOH) for five minutes.
5.2.4.1.6 Leave for 15 minutes in raw water.
5.2.4.1.7 Test with standard calibration buffer solution.
5.2.4.1.8 If electrode still fail to restore the normal electron response.
5.2.4.1.9 The Electrode rejuvenation steps repeat.
5.2.4.1.10 If response does not improve, then the electrode has completed its useful life and same shall be replace with a new electrode.
5.3 CALIBRATION
Frequency: Daily (Prior to use)
5.3.1 Before starting the calibration make sure that correct measurement mode is selected.
5.3.2 Wash the electrode thoroughly with de-ionized water or rinse solution.
5.3.3 Do not wipe the electrode, this cause a built up of electrostatic charge on a glass surface.
5.3.4 Maintain the temperature of buffers to 25 ◦C to ± 2 ◦C, unless otherwise specified in the individual monograph and dip the electrode along with the temperature sensor into the buffers.
5.3.5 Perform minimum 2 point calibration using standard buffers pH 4.01 and pH 7.01.
5.3.6 Dip the electrode into the calibration buffer. The end of electrode must be completely immersed into the sample. Stir the electrode gently to create homogenous sample.
5.3.7 Press the Cal key to enter the calibration mode. The CAL indicator will be shown.
5.3.8 The primary display will show the measured reading, while the smaller secondary display will indicate the pH standard buffer solution reading.
5.3.9 Weight for measured displayed value to stabilize.
5.3.10 Press the ENTER key to confirm the calibration. The meter is now calibrated to the current buffer.
5.3.11 First rinse the electrode with de-ionized water, which is followed by next buffer solution and place it in to the buffer solution.
5.3.12 Follow the same step for next buffer.
5.3.13 When all the calibration points are setup, the meter returns to its measurement mode automatically.
6. RELATED DOCUMENTS
Operational Log Book Format – Annex. I
Cleaning Log Book Format – Annex. II
Calibration Report Format – Annex. III
7. DISTRIBUTION INDEX
Original Copy will be retained by Quality Assurance Department.
DISTRIBUTION INDEX
Distributed To Copy No. Received By/Date
Quality Control Department 01
8. ABBREVIATIONS
Q.C Quality Control Department
HCl Hydrochloric Acid
H2SO4 Sulfuric Acid
NaOH Sodium Hydroxide
9. REVISION HISTORY
Revision No Issue Date Supersedes
Reason of Change/ Description
Revision No. Dated
00 25-12-2015 NA NA First Version