CALIBRATION OF AUTOTITRATOR AND ELECTRODES

• OBJECTIVE:

To lay down the procedure for Calibration of auto titrator and electrodes.

• SCOPE:

• This SOP is applicable to the procedure for Calibration of auto titrator and electrodes at {Company Name} {Location}.

• RESPONSIBILITY:
• Officer/Executive/Designee Quality Control – Shall be responsible for calibration of instrument as per SOP.
• Head/Designee Quality Control – Shall be responsible for ensuring compliance as per SOP.
• ACCOUNTABILITY:

QA Head shall be Accountable for implementation of SOP.

• PROCEDURE:
  • Calibration of burette:
    • Operate the instrument as per Sop, Rinse well the burette and fill the Burette with purified water.Take a clean, dry 10ml volumetric flask.Weigh the volumetric flask and note down the weight as W1.Set the dispense volume as 1 ml and dose the water into the Volumetric flask.Weigh the volumetric flask with water and note weight as W2.Repeat the above 3 steps for volumes 2,3,4,5,6,7,8,9,10 respectively.Mread = W2 – W1
    • Calculate the actually dispensed water in a volumetric flask using the formula:
• Vactual = Mread x Density
• Calculate the relative error using the formula
• Relative error = (Vactual –Vset) x 100/Vset
  • Density calculation:
    • Take a pycnometer and note down the empty weight (W1).
    • Fill the pycnometer with water, close the stopper provided and wipe off the excess water.
    • Now note down the weight of pycnometer with water at 25°C (W2).
    • Weight per ml of water = (W2-W1)/Volume of Pycnometer.
    • Enter the details of calibration in calibration record as per format-I.
    • Acceptance criteria: the average of Relative error should not be more than ± 0.5%
  • Auto titrator calibration:
    • Select a standard titration (KHP versus NaOH) suggested by Metrohm.
    • Prepare 0.1M NaOH solution and perform the standard titration for five times.
    • Calculate the molarity of NaOH for five titrations.
    • Calculate the RSD for molarity using the formula RSD = Standard Deviation % 100 Mean
    • Acceptance criteria: RSD value should not be more than ± 0.5%.
    • Enter the details in calibration record as per format-II.
    • If the calibration is not within the specified limits repeat the calibration. Report the Results to the department head for appropriate action.
  • Electrodes Calibration:
    • pH Electrodes:
      • Check the pH with three buffers 7.00, 4.01 and 10.01 and record the results in Format-III.
      • Acceptance criteria: The slope value should lie between 95% and 105% and Individual pH should lie within 0.05.
    • Solvotrode:
      • Check the mV value for buffers pH 4.0 and pH 7.0 and record the results in Format-IV.
      • Acceptance criteria: The difference between the two mV values should be Not less than150 mV.
    • Combined Ag ring Electrode:
      • Prepare a 0.1 N AgNO3 titrant and standardize using NaCl primary standard and check the purity of NaCl by carrying an assay titration and record the Results in Format-V.
      • Standardize and perform the titration as per GTP.
      • Acceptance criteria: The purity should lie within 99% to 101%.
    • Double Platinum Electrode Serial Number:
      • This is an electrode with two platinum wires so no calibration is required.
      • It is enough to ensure the two platinum wires are parallel to each other and clean it with a soft tissue dipped in acetone.
• REFERENCES:

Not Applicable

• ANNEXURES: 

         ENCLOSURES: SOP Training Record.

•  DISTRIBUTION:
• Controlled Copy No. 01  :          Head Quality Assurance
• Controlled Copy No. 02  :         Head Quality Control
• Master Copy                    :          Quality Assurance Department
• ABBREVIATIONS:

• REVISION HISTORY:             

CHANGE HISTORY LOG

Annexure-I
BURETTE CALIBRATION RECORD

Annexure-II
AUTO TITRATOR CALIBRATION RECORD

Annexure-III
ELECTRODE CALIBRATION RECORD-pH Electrode

Annexure-IV
ELECTRODE CALIBRATION RECORD-SOLVOTRODE

Annexure-V
ELECTRODE CALIBRATION RECORD-Combined Ag ring