Use of Water Standards

Video displays how to prepare and use a water standard in a Karl Fischer Coulometry Titration. | View Products | Multimedia Guide on CD | | Questions /Comments? |

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HYDRANAL® Water Standard:

Reliability

Coulometry is often referred to as an "absolute method", which in turn implies an "absolute" and total reliability of the results. However, there are various sources for error in the titration results - inaccurate administration of the sample, moisture in the titration cell, spent or unsuitable reagents, penetration of reductive substances from the cathode compartment through the diaphragm, side reactions which produce water, poisoned electrodes and instrumentation defects, to name a few. It is, hence, recommended that the recovery rate of water should be determined at regular intervals.
A control determination is relatively simple to perform: 1.0 g (exactly weighed by difference) of HYDRANAL®-Water Standard 0.10 or 1.0 is injected into the titration cell using a calibrated syringe to determine the water content. Recovery rates for water of ± 0.03 mg water for HYDRANAL®-Water Standard 1.0 or ± 0.001 mg/g for HYDRANAL®-Water Standard 0.10 (the values indicated on the certificate) are considered acceptable. A control titration can be carried out following a series of water determinations; it should be conducted if the reagent or equipment appears suspect. A daily control will give the analyst additional assurance.