I.
PURPOSE:
To provide a procedure for the Operation & calibration of autotitrator, Metrohm
831 KF Coulometer.
II.
SCOPE :
This procedure is applicable for the autotitrator being used for the analysis by
831 KF Coulometer in the Quality Control department.
III.
RESPONSIBILITY :
It is the responsibility of all the personnel involved in the analysis using of the
instrument.
IV.
V.
DOCUMENT REFERENCE:
SOPs :
Core procedure calibration of equipment.
Forms :
Calibration of 831 KF Coulometer
OPERATION:
PRELIMINARY CHECK:
1.1
Check and ensure that the instrument is clean and free from dust.
If not, clean the instrument using a soft cloth and a soft brush.
1.2
Check whether the molecular sieves are dry, by checking the colour of
moisture
indicator. The indicator is blue in dry condition and colourless if there is
excess
1.3
moisture, if not replace and keep the old one for drying.
Put on the ‘Mains’ of the instrument and switch on the stirrer assembly unit.
1.4
Check whether the electrode is filled with electrolyte.
1.5 Remove the solution filled in burette by pressing “DOS”. Drain it to waste.
1.6 Press “FILL” to fill the burette with titrant.
2.0
THE SYSTEM CONSISTS OF :
2.1
831 KF Coulometer.
2.2
728 Stirrer.
2.3
831 KF Coulometer - keyboard.
3.0
OPERATION:
3.1
Switch on the instrument 831 KF Coulometer.
3.2
Switch on the instrument 728 Stirrer.
3.3
Fill the Titration with 80-100 mL of KF Combi coloumat 1.09255.0500
(Merck –make) or equivalent.
3.4
Change the Combi coloumat solution for every week or when the desired drift is
not
After 20 minutes time of switching the instrument on..
3.5
Switch on the instrument and the stirrer with button.
3.6
Press the start button to start the determination.
3.7
Add the sample after the drift is less than 10g/min.
3.8
Enter the sample weight and press start the moisture content will be displayed
after the titration.
3.9
Take the print out.
VI. Calibration:
Calibration frequency: Once in every three months.
1.0 Precision & Accuracy
1.1 Determine the water content with 0.1%, 0.01% and 1.0% certified water
standards 5times.
1.2 Each with 1 mL of standard with Syringe.
1.3 Determine the water content in % Mode.
Procedure:
1.4 Break the vial of standard and draw 1 mL of standard rinse it.
1.5 Draw 5 mL of sample
1.6 Inject about 1mL of sample into the titration vessel.
Acceptance criteria:
Precision:
 The % RSD should not be more than 2.0 %
Accuracy:
 For 0.01% - Mean result obtained should be 0.0084 to 0.0104
 For 0.1% - Mean result obtained should be 0.0982 to 0.1022.
 For 1.0% - Mean result obtained should be 0.9960 to 1.0160.
2.0 Linearity :
2.1 Calculate the correlation coefficient value of the water standards against the time for
titration.
Acceptance criteria:
 Correlation coefficient should not be less than 0.95.