Operation and Calibration Procedure for pH Meter

1.0 Objective
To lay down a Procedure for Operation and Calibration for Procedure for pH Meter.
2.0 Scope
This Standard Operating Procedure is applicable for Operation and Calibration for Procedure for pH Meter in Quality Control Department of abc company.
3.0 Responsibility
3.1 Concerned Officer/Executive shall be responsible to follow this SOP.
3.2 Department Head or his designee shall be responsible to implement and ensuring to compliance of this SOP.
4.0 Abbreviations and Definitions
SOP : Standard Operating Procedure
QC : Quality Control
QA : Quality Assurance
No. : Number
KCl : Potassium Chloride
HCl : Hydrochloride acid
Mv : Millvolt
5.0 Procedure
5.1 Operation procedure
5.1.1 Ensure that Instrument clean and ready for use.
5.1.2 Switch “ON” the mains power supply.
5.1.3 Switch “ON” the instrument. Two line display shall read as follow.
LABINDIA INSTRUMENT
pH ANALYSER V1.01
5.1.4 Select the pH mode.
5.1.5 Instrument get stabilized itself with message on the screen “Wait! Stabilizing…” which shows the Instrument shall be checking electrode signal stability and once the signal steady it shows the measured pH, mv and temperature.
5.1.6 Remove the pH electrode from the storing solution and rinse it with distilled water 2-3 times, soak the excess water with tissue paper and insert the pH electrode and temperature sensor in the sample beaker.
5.1.7 Select temperature mode (Automatic or Manual).
5.1.7.1 For Automatic temperature compensation to be considered during measurement at 25° C.
5.1.7.2 For Manual temperature compensation, measure the solution temperature with external thermometer and then enter the correct temperature value.
5.1.8 Stir the sample solution keeping the pH electrode and temperature sensor immersed.
5.1.9 Note down the reading direct from the display.
5.1.10 After end of the pH measurement press the “RESET” key.
5.1.11 Lift the electrode with temperature sensor and rinse with purified water 2-3 times.
5.1.12 At the end of shift, switch “OFF” the instrument and main power supply.
5.2 Calibration
5.2.1 pH meter shall be calibrated once in daily in the morning or before it intended use.
5.2.2 Daily calibration shall be performed with minimum three standard pH buffer solutions.
5.2.3 The three standard pH buffer solutions should be in the range of 3 to 5, 6 to 8 and 9 to 11.
5.2.4 Prepare the standard pH buffer solutions as given below or use readily available certified

standard buffer Tablets / Capsules / Solutions.
5.2.5 Preparation of Buffer solutions (As per IP):
5.2.6 pH 4.01 Buffer: Weigh an accurately about 1.021g (1.021% w/v) of potassium hydrogen phthalate in

to a 100ml volumetric flask, dissolve and make up with purified water.
Note: Potassium hydrogen phthalate should be dried at 110° to 135° for 2 hours before use.
5.2.7 pH 9.18 Buffer: Weigh an accurately about 0.3814g (0.3814% w/v) of sodium tetra borate in

to a 100ml volumetric flask, dissolve and make up with purified water.
Note: Store protected from carbon dioxide.
5.2.8 pH 6.87 Buffer: Weigh an accurately about 0.348g (0. 0.348% w/v) of potassium dihydrogen phosphate and 0.355g (0.355% w/v) of anhydrous disodium hydrogen phosphate in to a 100ml volumetric flask, dissolve and

make up with purified water.
Note : Both potassium dihydrogen phosphate and disodium hydrogen phosphate should be dried

at 110° to 135° for 2 hours before use.
5.2.9 Use the standard pH buffer solutions for 7days from the day of preparation.
5.2.10 To prepare the readily available standard buffer Tablets / Capsules / Solutions, follow

instructions of manufacturer as given separately.
5.2.11 Calibrate the instrument using three level standard buffer solutions at 25°C ±2°C.
5.2.12 Observed pH of the three ranges buffer solutions should be within  0.02 of standard pH.
5.2.13 If the observed pH value found to be more than  0.02 of standard pH, then calibrate the

instrument against the standard buffer solutions as per bellow given procedure.
5.2.14 Select the pH mode by pressing the button named PH on the instrument.
5.2.15 Instrument get stabilized itself with message on the screen “Wait! Stabilizing…” which shows

the Instrument shall be checking electrode signal stability and once the signal steady it shows the

measured pH, mv and temperature.
5.2.16 Remove the pH electrode from the storing solution and rinse it with distilled water 2-3 times,

soak the excess water with tissue paper and insert the pH electrode and temperature sensor in the beaker of buffer solution of pH 6.0 to 8.0.
5.2.17 Select the memory clear mode by pressing the button named MEM CLEAR on the instrument.
5.2.18 The instrument will display:
1) Reading
2) Cailb
3) All
5.2.19 Clear the calibration and all the readings displayed by the instrument yesterday by pressing

the button named “3” on the instrument.
5.2.20 All the memory will be clear with a message on the screen Memory Cleared.
5.2.21 Again the instrument get stabilized itself with message on the screen “Wait! Stabilizing…” which

shows the Instrument shall be checking electrode signal stability and once the signal steady it shows

the measured pH, mv and temperature.
5.2.22 Press the button “8” named “CAL 7” for calibration of the instrument with the buffer solution of pH 6.0 to 8.0.
5.2.23 Stir the buffer solution keeping the pH electrode and temperature sensor immersed.
5.2.24 Automatic temperature compensation to be considered during measurement at 25°C.
5.2.25 It will display a message on the screen “No Data”.
5.2.26 Press ENTER.
5.2.27 The Instrument shall be checking mv stability with a message displayed on the screen “Enter if stable”.
5.2.28 When the displayed mv reading will be stable, press “ENTER”. it shows the measured

pH, mv and temperature. Ie

pH=7.00 T=25.0°C
mv=+ 000.0

5.2.29 After end of the calibration with buffer solution of pH 6.0 to 8.0, press the “RESET” key.
5.2.30 Again select the pH mode by pressing the button named “PH” on the instrument.
5.2.31 Press the button “7” named “CAL 4” for calibration of the instrument with the buffer solution of pH 3.0 to 5.0.
5.2.32 The Instrument shall be checking pH stability with a message displayed on the screen “Enter if stable”.
5.2.33 When the displayed pH reading will be stable, press “ENTER”. it displays “Calibration over” and

then shows the measured pH, mv and temperature.
5.2.34 After end of the calibration with buffer solution of pH 3.0 to 5.0, press the “RESET” key.
5.2.35 Again select the pH mode by pressing the button named “PH” on the instrument.
5.2.36 Press the button “9” named “CAL 9.2” for calibration of the instrument with the buffer solution of pH 9.0 to 11.0.
5.2.37 The Instrument shall be checking pH stability with a message displayed on the screen “Enter if stable”.
5.2.38 When the displayed pH reading will be stable, press “ENTER”. It shows the measured pH, mv and temperature.
5.2.39 After end of the calibration with buffer solution of pH 9.0 to 11.0, press the “RESET” key.
5.3 General
5.3.1 Record the instrument usage in the form as given in Annexure-1.
5.3.2 Record the observations of calibration in the form as given in Annexure-2.
5.3.3 Affix the label to the standard buffer solutions as given in Annexure-3
5.3.4 Frequency of Calibration: daily/after preparation of standard buffer solution/after every maintenance job.
5.3.5 Calibration of temperature sensor shall be done by external agency every year.
5.3.6 Clean the outer part of the pH meter and surrounding by lint free cloth before and after the use.
5.3.7 Remove dirty spots or stains, if any from main body of the Instrument using collin cleaner.
5.3.8 Do not use acid/alkali solutions or solvents for the cleaning of the Instrument.
5.3.9 After every pH measurement, wash electrode and temperature sensor probe with purified water

and wipe with soft tissue paper before dipping in any liquid under test.
5.3.10 The electrode should remain dipped in saturated solution of “KCl” before and after using it.
5.3.11 Never touch the lower sensitive bulb of the electrode by hand or any other hard surface.
5.3.12 For reactivating the electrode dip electrode in 0.1 N HCl for 24 hrs every weak end at the working shift.
5.3.13 Frequently change storing solution (saturated solution of “KCl”) in which the electrode remains dipped.
6.0 Forms and Records
6.1 Instrument usage log – Annexure-1
6.2 Calibration Record – Annexure-2
6.3 Buffer solution status label – Annexure-3
7.0 Distribution
7.1 Master copy – Documentation Cell (Quality Assurance)
7.2 Control copy – Quality Control
8.0 History