Introduction
In principle, the 774 Oven Sample Processor can be used with all samples that release water when heat is applied. However, the KF oven method is essential whenever direct volumetric or coulometric Karl Fischer titration is impossible because the sample contains interfering components or, owing to its consistency, is difficult to place in the titration vessel.
The combination of the 774 Oven Sample Processor with a Metrohm coulometer is ideal for samples with a low water content. Food, pharmaceutical products, plastics or petrochemical products can be analyzed automatically and extremely accurately. On the other hand, a Metrohm volumetric Karl Fischer titrator is preferred for a sample with a very high water content.
The water is driven out from the heated sample by a stream of dry carrier gas and transferred to the titration vessel, where the water is determined by a KF titration. For temperature-sensitive samples, e.g., food, the water can be released gently at lower temperatures by simultaneous extraction with methanol. In this way, it is possible to prevent any water released by decomposition or any water of crystallization that may split off from being determined and therefore produce incorrect results.
This Application Bulletin uses examples from the food, pharmaceutical, plastics and petrochemical industries to describe automatic Karl Fischer water determination using the 774 Oven Sample Processor and the 756 KF Coulometer. Information applying to the combination of the Oven Sample Processor with a volumetric KF titrator (758 KFD Titrino or 841 Titrando®) is given in brackets.
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