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SOP for Calibration pH Meters


Standard operating procedure to calibrate the pH meter using the standard buffer solutions.

1.0  OBJECTIVE 

       To calibrate the equipment for reliable and accurate results.

2.0  SCOPE

       This procedure is applicable for pH meters installed at Quality control laboratory.

3.0  RESPONSIBILITY

3.1  Doing      : Technical Assistant
3.2  Checking : Executive /Manager

4.0  ACCOUNTABILITY

       Head of the Department

5.0  PROCEDURE

5.1  Operate the instrument as per respective Standard Operating Procedure.
5.2  Use Certified Standard pH buffer to set the instrument at pH 7.00 (with 7.00 pH buffer) and pH 4.00 (with 4.00 pH buffer) at 25o C.
5.3  Take 100 ml buffer pH 4.0 & pH 7.0 from the Certified buffer bottle in a glass bottle. Discard the Standard pH buffer after one month.
5.4  Prepare different pH solutions of 0.05 M Potassium biphthalate, 0.05 M equimolol phosphate, 0.01 M sodium tetraborate and Calcium Hydroxide (saturated solution at 25oC)
5.4.1  Solution A : Preparation of 0.05 M Potassium Biphthalate (pH 4.01)
          Dissolve 10.12 gm. of KHC8H4O( previously dried at 110 oC for 1 hour) in water to make 1000 ml.
5.4.2  Solution B : Preparation of 0.05 M equimolol phosphate buffer( pH 6.86)
           Dissolve 3.53 gm. of Na2HPO4 and 3.39 gm. of KH2PO4 (each previously dried at 120oC for 2 hour) in water to make 1000 ml.
5.4.3  Solution C : Preparation of 0.01 M  Sodium tetraboarte buffer( pH 9.18)
          Dissolve 3.80 gm.of Na2B4O7.10 H2O in water to make 1000 ml. Protect the solution from absorption of carbon dioxide.
5.4.4  Solution D : Preparation of  Saturated solution of  Calcium hydroxide at 25oC (pH 12.45)
          Shake an excess of calcium hydroxide with water and decant at 25oC before use. Protect the solution from absorption of carbon dioxide. (Prepare fresh solution when required)
5.5  Check the pH of above buffer solutions. It should be within + 0.07. Record the value in the prescribed  Annexure-II
5.6  Check the pH of Certified buffer pH 4.0 & pH 7.0. It should be within +0.02 pH limit of labelled value. Record the value as per Annexure-II

5.7  Discard buffer solution A, B and C after three month.

5.8  Frequency of calibration :- 15 days.

5.9  Daily calibration

5.9.1  Repeat  the same procedure for daily calibration of pH meter using solution A, B and solution C and record value as per annexure-I
5.10  If it is out of specified limit, follow the S.O.P.

Related: Principle and Working of pH Probes

6.0  ABBREVIATIONS

6.1  oC = Degree centigrade
6.2  Na2B4O7.10H2O = Sodium Tetraborate Decahydrate
6.3  U.S.P. = United state pharmacopoeia
6.4  Na2HPO4 = Disodium hydrogen orthophosphate
6.5  KH2PO= Potassium dihydrogen orthophosphate
6.6  gms. = Grams.
6.7  S.O.P.No. = Standard operating procedure number
6.8  KHC8H4O4  = Potassium Biphthalate


ANNEXURE-I
Q. C. Department
 DAILY CALIBRATION RECORD
Name of  the Instrument     :  pH METER
Make                                                :  
Model  No                                      :                                  
IDENTIFICATION NO.                    :
 ______________________________________________________________________________
Primary standard : Certified  buffer (pH 4.00 &pH 7.00)
OBSERVATION CHART
Date
0.05 M
Potassium
Biphthalate
( 4.01+ 0.07)
0.05 M equimolol
phosphate
( 6.86+ 0.07)
0.01 M 
sodium        Tetraborate
( 9.18+ 0.07)
Check point
( if applicable)
Calibrated by
Checked by






































ANNEXURE-II
Q. C. Department
  CALIBRATION RECORD OF pH METER
Name of  the Instrument    :  pH METER
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)
OBSERVATION : 
Buffer
Theoretical pH
Value(At 25oC)
Observed value
Tolerance
Remarks
0.05 M Potassium Biphthalate
4.01
+ 0.07
0.05 M equimolol phosphate
6.86
+ 0.07
0.01  M sodium Tetraboarte
9.18
+ 0.07
Calcium hydroxide (saturated)
12.45
+ 0.07
Standard  Certified buffer
6.98
+ 0.02
Standard Certified buffer
4.01
+ 0.02

Remarks                              :
Calibration date                   :                                                                     
Calibration due date            :
Calibrated  by                     :
Checked  by                       :
Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
Email: .moc.enilediugamrahp@ofni Need Help: Ask Question


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