Digital pH-meter Calibration SOP


Digital pH-meter Calibration SOP
1.0  OBJECTIVE:
To lay down the calibration procedure for reliable and accurate results.
2.0  SCOPE:
This shall be applicable to the pH meter of Quality Control Laboratory.
3.0  RESPONSIBILITY:
3.1  Technical Assistant/ Helper.
3.2  Q.C Analyst.
4.0  ACCOUNTABILITY:
4.1  Manager-Quality Control.
5.0  MATERIAL AND EQUIPMENT:
5.1  pH meter.
5.2  Analytical weighing balance.
5.3  Magnetic stirrer.
5.4  desiccator
5.5  Glassware (6 beaker of 1000.0ml, 2 beakers of 100.0ml, 1 pipette, 1 stirrer, spatula).
5.6  Standard certified buffer bottle of pH 4.00 and 7.00.
5.7  Potassium hydrogen phthalate 10.13g.
5.8  Potassium dihydrogen phosphate 3.39g.
5.9  disodium hydrogen phosphate 3.53g
5.10    Disodium tetraborate 3.80g.
5.11    Calcium hydroxide.
5.12    Carbon dioxide-free water.
6.0  PROCEDURE:
6.1  Firstly clean the pH meter with clean dry cloth, according to SOP.
6.2  Operate the pH meter according to SOP for operation of pH meter i.e. SOP.
6.3  Use certified standard pH buffer to set the instrument at pH 7.00 (with 7.01 pH buffer) and pH 4.00 (with 4.01 pH buffer) at 25oC.
6.4  Take 2 beakers of 100.0ml add buffer pH 4.0 & 7.0 separately, from the certified buffer bottle in a glass bottle. Discard the standard pH buffer after one month.
6.5  Prepare different pH solutions.
6.5.1        Potassium hydrogen phthalate 0.05M:
6.5.1.1  Firstly weigh potassium hydrogen phthalate 10.13g by using analytical weighing balance, operate it according to SOP.
6.5.1.2  Dry the potassium hydrogen phthalate sample for 1hr at 110±2oC in desiccator previously.
6.5.1.3  Take a beaker of 1000.0ml and add potassium hydrogen phthalate 10.13g in sufficient Carbon dioxide-free water, stir it by using magnetic stirrer.
6.5.1.4  Dilute it to 1000.0ml with the same solvent.
6.5.2        Potassium dihydrogen phosphate 0.025M+disodium hydrogen phosphate 0.025M:
6.5.2.1  Weigh potassium dihydrogen phosphate 3.39g & disodium hydrogen phosphate 3.53g by using analytical weighing balance, operate it according to SOP.
6.5.2.2  Dry both the potassium dihydrogen phosphate & disodium hydrogen phosphate samples for 2hr at 120±2oC in desiccator previously.
6.5.2.3  Take a beaker of 1000.0ml and add potassium dihydrogen phosphate 3.39g & disodium hydrogen phosphate 3.53g in sufficient Carbon dioxide-free water, stir it by using magnetic stirrer.
6.5.2.4  Dilute it to 1000.0ml with the same solvent.
6.5.3        Disodium tetraborate 0.01M:
6.5.3.1  Weigh disodium tetraborate 3.80g by using analytical weighing balance, operate it according to SOP.
6.5.3.2  Take a beaker of 1000.0ml and add disodium tetraborate 3.80g in sufficient Carbon dioxide-free water, stir it by using magnetic stirrer.
6.5.3.3  Dilute it to 1000.0ml with the same solvent.
6.5.3.4  Store protected from atmospheric carbon dioxide.
6.5.4        Calcium hydroxide, saturated at 25oC:
6.5.4.1  Take an excess of calcium hydroxide.
6.5.4.2  Take a beaker of 1000.0ml and add excess of calcium hydroxide in sufficient Carbon dioxide-free water, stir it by using magnetic stirrer.
6.5.4.3  Store protected from atmospheric carbon dioxide.
6.6  Check the pH of above buffer solutions. It should be within ±0.07. Record the value in the prescribed Annexure-2.
6.7  Check the pH of certified buffer pH 4.0 & 7.0. It should be within ±0.02 pH limit of labeled value. Record the value as per Annexure-2.
6.8  Discard buffer solution 6.5.1, 6.5.2 & 6.5.3 after 3 month.
6.9  Record the result on the “Calibration Record”, “Calibration Log Book” & paste the “Calibration Status Sticker” on pH meter.
6.10    Frequency of calibration: 15 days.
6.11    Daily calibration:
6.11.1    Repeat the same procedure for daily calibration of pH meter using solution 6.5.1, 6.5.2 & 6.5.3 and record value as per Annexure-1.
6.12    If it is out of specified limit, follow the S.O.P.
6.13    pH meter temperature sensor:
6.13.1    Keep the temperature sensor probe of reference calibrated digital thermometer in the beaker containing purified water of about 35oC.
6.13.2    Add cold purified water slowly drop wise and bring the temperature between 27oC to 30oC.
6.13.3    Compare the temperature shown by reference calibrated digital thermometer and pH meter & record it in format as Annexure-3.
6.13.4    Add purified water in some more quantity slowly drop wise to bring the temperature between 26oC to 23oC.
6.13.5    Compare the temperature shown by reference calibrated digital thermometer and pH meter & record it in format as Annexure-3.
6.13.6    Add cold purified water slowly drop wise and bring the temperature between 20oC to 22oC.
6.13.7    Compare the temperature shown by reference calibrated digital thermometer and pH meter & record it in format as Annexure-3.
6.13.8    Acceptance criteria: ±3oC.
6.13.9    Frequency of calibration: Twice in year.
7.0  REVISION LOG:
Revision No.
Effective Date
Reason
00

New SOP

8.0  REFERENCES:
8.1  The British Pharmacopoeia. Vol V., Official Monograph / Determination of pH values: 2015, pp. 252-253.
9.0  ANNEXURES:
Annexure 1: Daily calibration record.
Annexure 2: Calibration record of pH meter.
Annexure 3: pH meter temperature sensor records.







Annexure: 1
Daily calibration record
Name of the Instrument: ________________
Make: ________________________________
Model No.: ____________________________
Identification No.: ______________________
Primary Standard: Certified buffer (pH 4.00 & pH 7.00).
Observation Chart
Date
Potassium hydrogen phthalate 0.05M
Potassium dihydrogen phosphate 0.025M +disodium hydrogen phosphate 0.025M
Disodium tetraborate 0.01M
Check point (if applicable)
Calibrated by
Checked by







































                                                         

                                                          Annexure: 2
Calibration record of pH meter
Name of the Instrument: ________________
Make: ________________________________
Model No.: ____________________________
Identification No.: ______________________
Primary Standard: Certified buffer Primary Standard: Certified buffer (pH 4.00 & pH 7.00).
Batch No.: ___________ (pH 7.00).
Batch No.: ___________ (pH 4.00).
Observations
Buffer
Theoretical Ph value (at 25oC)
Observed value
Tolerance
Remarks
Potassium hydrogen phthalate 0.05M




Potassium dihydrogen phosphate 0.025M +disodium hydrogen phosphate 0.025M




Disodium tetraborate 0.01M




Calcium hydroxide (saturated)




Standard certified buffer




Standard certified buffer




Remarks: _______________________________________________________________
Calibration date: __________________    Calibration due date: __________________
Calibrated by: ____________________     Checked by: _________________________


Annexure: 3
pH meter temperature sensor records
Ref. No.: ________________
Issue date: ______________
Issued by: _______________
Calibrated ref. digital thermometer: ____________________
Ref. thermometer calibration date: _____________________
Ref. thermometer certificate No.: _______________________
Ref. thermometer calibration due date: __________________
pH meter ID. No.: ____________________________________
Observations
Set range
Observations
Difference
Tolerance
Temp. as read on pH meter
Temperature as read on display of ref. thermo.
27oC to 30oC




±0.3oC
26oC to 23oC



20oC to 22oC



Remarks: __________________________________________________________________
Calibration date: _____________________
Next calibration date: _________________
Calibrated by: _______________________
Checked by: _________________________




10.0    ABBREVIATIONS:
Abbreviation
Expanded Form
SOP
Standard operating procedure
&
And
No.
Number  
Ltd.
Limited
Q.C
Quality control
Q.A
Quality assurance
QCEB
Quality control equipment calibration
ml
Milliliter
g
Grams
oC
Degree centigrade
M
Molar
B.P
British pharmacopoeia
Vol
Volume
Ref.
Reference
ID.
Identity


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