Metrohm has brought out the 860 KF Thermoprep, opening up possibilities for determining water content by the Karl Fischer method.
With the 860 KF Thermoprep, samples are no longer placed in the oven in weighing boats, but each sample is now contained in its own tightly sealed sample vial.
Because the sample is not put directly into the titration cell, water determination of 'difficult' samples is now possible - these are samples that are either insoluble, react with the KF reagent or that cannot be placed directly in the titration vessel for other reasons..
Difficult samples can be caused by substances such as plastics or inorganic salts that only release their water slowly or at high temperatures.
Further problems can be caused by the low solubility of certain samples (for example, plastics) in alcohols.
Traditional methods in these cases recommend the use of toxic solvents to promote dissolution, or alternatively, extensive sample preparation procedures.
If a sample is introduced directly into the titration cell, the latter can be strongly contaminated, making it necessary to exchange the titration solution and clean the cell frequently.
There are also various substances such as ascorbic acid that undergo side reactions with KF reagents, falsifying the result.
Examples of difficult samples include oil (containing additives), plastics, paint, pharmaceutical products, wound-care products and hair.
The 860 KF Thermoprep from Metrohm drives off moisture from solid and liquid samples for the subsequent coulometric or volumetric determination of the water content by the Karl Fischer method.
Its temperature range is 50-250 degrees centigrade.
The oven can be used with all volumetric and coulometric KF titrators.
The 860 KF Thermoprep is available in three options: as an oven on its own, as an oven in conjunction with a coulometric KF (for low-level water) and as an oven with a volumetric KF (for high-level water).
The benefits are that it produces strictly reproducible analysis conditions for all samples, which is demonstrated in the considerably improved precision of results; it means manual sample preparation is reduced to a minimum; it saves a considerable amount of time; it prevents contamination of the oven by the sample, meaning there are no carryover and memory effects; and, finally, because the carrier gas goes directly through the sample rather passing over it, it improves water release from the sample.
