How to standardize KF reagents
Updated: Apr 2
Karl Fischer (KF) reagent is a mixture of iodine, sulfur dioxide, and a base that is used to react with water in the sample during the Karl Fischer titration method for moisture estimation. To ensure the accuracy and reliability of the KF method, it is essential to standardize the KF reagent periodically.
The standardization of KF reagent involves the determination of its exact water content by titration with a primary standard substance, such as potassium hydrogen phthalate (KHP), which has a known water content or by injecting a measured quantity of water itself. The procedure for the standardization of KF reagent is as follows:
Preparation of the KF reagent: Get a fresh bottle of KF reagent from a reputable manufacturer. Lesser known manufacturers tend to dilute or adulterate their sample creating issues during standarding and sample testing.
Preparation of the primary standard: The primary standard substance, such as KHP, is accurately weighed and dissolved in the same solvent used for the KF reagent. Alternatively, measure 6-7 micro litre of water in a syringe.
Titration of the primary standard: The primary standard solution is titrated with the KF reagent until the endpoint is reached. The endpoint is determined by the appearance of change in colour which is accurately recorded as a change in millivolt on the digital titrator.
Calculation of the KF reagent concentration: The water content of the primary standard substance is used to calculate the concentration of the KF reagent. The KF reagent's water content is then determined by dividing the amount of water in the primary standard substance by the volume of KF reagent used in the titration. The Mayura Analytical titrator automatically calculates the concentration and displays the values.
The standardization of KF reagent is an essential step in the Karl Fischer titration method, as it ensures the accuracy and reliability of the moisture estimation results. Regular standardization of the KF reagent is necessary to account for any changes in its water content due to factors such as storage conditions or contamination.
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