Calibration and Operating Procedure for pH Meter

  • Objective:To lay down procedure for Calibration and Operation of pH Meter.
  • Scope:This standard operating procedure is applicable for formulation plant of Pharmaceutical company name with location.

Make: Mettler Toledo.

  • Responsibility
    • Trained worker / Operator shall be responsible for performing the calibration and operation of the equipment as per this SOP.
    • Production Supervisor / Officer shall be responsible for implementation of this SOP.
    • Head-Production / designee shall be responsible for compliance of this SOP.
  • Abbreviations and Definitions

pH –   – log [H+]

MTC –  Manual Temperature Compensation

ATC –  Automatic Compensation

HDPE – High Density Poly Ethylene

SOP –  Standard Operating Procedure

mv – milivolt

QA – Quality Assurance

  • Procedure
    • Calibration Procedure:
      • Take 20 ml Hamilton buffer solution from buffer bottle in its measuring cup by pressing the bottle.
      • Use this solution within one week. calibrate the pH meter weekly.
      • 1st-Point Calibration for pH “7.00”
        • Remove the cover from tip of the electrode.
        • wash electrode with purified water and dry with tissue paper
        • Set the temp. at 25ºC by pressing temp key and Up/ Down scroll key.
        • For Auto Mode, place the electrode in a calibration buffer of pH 7.00 and press ‘Cal’
        • End point reaches automatically. It shall display pH at particular temperature.
        • For manual Mode press A.
        • Meter shall display value of calibrated pH and freeze the buffer value.
        • To return to Sample measurement press Read A key.
      • 2nd – Point Calibration for pH “4.01”:
        • After 1st point calibration, wash electrode with purified water and dry with tissue paper.
        • Place the electrode in solution of pH 4.01 buffer and press ‘Cal’
        • pH meter shall display reading automatically when endpoint reaches and calibrated, for manual mode press Read A key.
        • pH meter shall display pH value on the screen and value shall be freezed.
        • To return in measurement by pressing Read A key.
      • 3rd – Point Calibration for pH “9.21”
        • Perform the steps as in 1st and 2nd end point calibration.
      • Frequency of Calibration:
        • Calibrate the pH meter weekly.
        • Record all the observation in pH calibration record (Annexure-1).
        • After calibrations affix ‘calibrated’ tag on the equipment.
      • Operating Procedure:
        • Temperature Setting:
          • Press Temperature key to set the Temperature in manual mode and its value can be increase or decrease by using UP/DOWN scroll key.
          • By press READ A key for confirming the setting?
          • By pressing and holding pH/ mv key printer signal shall be display in screen and print shall be obtained.
        • Place the electrode in the sample and press ‘ReadA’ key for the measurement.
        • Display shows the actual pH of the sample.
        • Wait till the sensor output valve has been stabilized, the display freezes automatically and ‘A’ appears on the screen.
        • By pressing and holding the ‘read A’ key, auto and manual end point mode can be interchanged.
        • To measure mv press pH/mv key, during the pH measurement.
      • Forms and Records
        • pH METER CALIBRATION RECORD – Annexure-I
      • Distributions
        • Master Copy – Documentation Cell (QA)
        • Controlled Copies – Production and Quality Assurance
  • History
Date Revision


Reason for revision
00 New SOP


                                       pH METER CALIBRATION RECORD

Equipment ID No.:



Date and Time




1st Point Calibration 2nd Point Calibration 3rd Point Calibration  




Done By



Checked By



Due Date

Buffer Solution


Observed Value

Buffer Solution


Observed Value

Buffer Solution


Observed Value


OK / Not Ok

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