SOP for Operation of Karl Fisher Titration Instrument

PURPOSE

To provide a procedure for the operation of Karl Fisher titrator, Manufacturer & Model: Lasco, KFTA.

SCOPE

Applicable for Karl Fisher titrator instrument in the quality control laboratory.

RESPONSIBILITY

All QA/QC students.

DEFINITION

Karl Fisher titrator instrument used to determine the water content of a sample.

• A Macro Karl Fischer Instrument uses standardized volumetric solution to determine the amount of moisture in samples, and is used when the expected result is between 1 mg to 100 mg of water.
• A Micro Karl Fischer Instrument uses an electrical current (coulometry) to determine moisture in samples, and is used when the expected result is between 10 μg to 10 mg of water.

PROCEDURE

• Ensure the calibration status is valid.
• Ensure the instrument is clean and free from dust.
• Switch on the instrument by using the switch provided on the rear side of the left.
• When the instrument is ON, the Green LED ‘O’ will glow.
• Fix Karl Fischer Reagent (KFR) bottle by screwing on the plastic cap, operating below, holding vertically, and closing the “T” joint connection tube.
• Air pressure in the KFR bottle increases and lifts KFR to fill the burette. When the level crosses the ‘0’ mark, remove the finger, Zero level gets automatically.
• Place the magnetic stirring paddle slowly by sliding it into the reaction vessel and fix the burette by lifting the burette assembly.
• Pour about 20 ml of methanol into the reaction vessel.
• Connect the jack wire to a reaction vessel and electrode terminals marked ‘e’ rear side of the instrument.
• Switch on the stirrer, set the required speed by using the regulator, and wait for 10 to 15 seconds for uniform stirring.

• Add KFR by drops into the reaction vessel by operating the burette valve. Until the pre-end point. Yellow LED glows ‘P’ is nearing the end point indication.

ALSO READ: What is the Acceptance Quality Limit (AQL)?

• Add KFR by drops slowly giving 10-20 seconds between additions until Red LED ‘E’ glows continuously for 30 seconds which indicates the end point of the titration (Neutralisation of methanol).
• Fill the burette with wh?
• Weigh 1ml syringe with a needle with a small quantity of distilled water
• Add 25-100mg into the reaction vessel and close the stopper. Start the magnetic stirrer, and titrate up to the end point (RED LED glows for 30 seconds).
• Note the burette reading and calculate the water equivalent of KFR by using the following calculation.

F = M/A

Where, 

M - mg in water;

A - Volume of KFR consumed.

Repeat the same and take the mean.

• Weigh the sample in the plastic spoon then add it to the reaction vessel.
• Fill the burette and start the stirrer.
• Wait until the sample dissolves, then add KFR up to the endpoint.
• Note the burette reading.

• Calculate the water content by using the following formula:

% of water content = B x F x 100 / W

Where, 

B - Volume of KFR consumed.

F - Factor

W - Weight of sample in mg.

• After completion of the analysis remove the KFR bottle from the plastic cap and fix the methanol bottle. Drain KFR from the burette fill methanol and wash the reaction vessel.
• Switch OFF the instrument and clean the place.

REFERENCE

Nil.

ABBREVIATION

SOP: Standard Operating Procedure

QC: Quality control

ml: Milliliter

REVISION HISTORY

Nil

ALSO READ: SOP for Operation and Calibration of Karl Fischer Apparatus