Karl Fischer water determination

Facility/equipment: Equipment

    Description

    Introduction

    To determine accurately the water content in a liquid sample, Karl Fisher titration can be used. The Karl Fisher titration can measure water content in low ppm levels, and detects only water and no other molecules or volatiles. This makes the system very suitable for determination of low water content in solvents.

    Principle

    Karl fisher water determination is an analytical water quantification method which makes use of a volumetric titration principle.

    The titration is based on the following chemical reaction:

    I2 + S02 + H2O ⇋ 2HI + H2S04

    1 mole of l2 is consumed by each mole of water, a basemust be added to drive the equilibrium reaction towards the right. The titration medium is known concentration of l2
    The reaction produces I-, making the liquid conductive, as soon as the reaction is completed I- is consumed and only I2 is present, creating a sudden drop in conductivity. This conductivity is measured by 2 electrodes in the solution.As soon as the reaction is complete the added amount of I2 is known and the water content can be calculated.
    Applications
    • Determination of water content in solvents• Determination of water in polymer dope solutions • Both free and bound water determination
    Limitations• pH must be between 5-7• No Dimethylsulfoxide measurements, as the solventreacts with the Iodine.

    Details

    Name795 KFT Titrino, Metrohm

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    Titration
    Water content
    Water
    Liquids
    Polymer solutions
    Dimethyl Sulfoxide
    Iodine
    Chemical reactions
    Electrodes
    Molecules