As shown in Formula (1) below, the Karl Fischer method uses Karl Fischer reagent, which reacts quantitatively and selectively with water, to measure moisture content. Karl Fischer reagent consists of iodine, sulfur dioxide, a base and a solvent, such as alcohol. I2+SO2+3Base+ROH+H2O 2Base+HI+Base+HSO4R ······ (1) As described below, this method can be used in both volumetric and coulometric titration systems. | |||
Coulometric Titration | |||
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Volumetric Titration
A dehydrating solvent suitable for the sample is placed in a flask. Titrant is used to remove all moisture from the solvent. The sample is then added. Titration is carried out using a titrant, the titer (mgH20/mL) of which has previously been determined. The moisture content of the sample is determined from the titration volume (mL). The end point is detected using the constant-current polarization voltage method. Figure 2 shows the components of typical commercially available automatic volumetric titration system. |
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