Although KF titration itself is a fast method, the sample preparation step can be time-consuming since water has first to be completely released from the sample prior to titration
The Karl Fischer (KF) titration has proven to be a reliable, accurate and reproducible analytical technique for the determination of the water content in many matrices.
The primary advantage is its high selectivity for water.
Although KF titration itself is a fast method (1- 2 minutes for a single analysis), the sample preparation step can be time-consuming, since water has first to be completely released from the sample prior to titration.
When several samples have to be determined, personnel are occupied for lengthy periods with monotonous activities, while they could be more efficiently used in performing other more demanding laboratory tasks.
By using an automatic titrator in combination with a sample changer, many samples can be titrated automatically without the need for the continuous presence of the operator.
Depending on the water content, the appropriate titrator must be selected.
For instance, when titrating small amounts of water (e.g <100ppm) by the coulometric KF technique, the water has first to be evaporated from the solid or liquid sample by means of an oven and carried over to the titration vessel by means of a dry gas stream.
On the other hand, samples having 1% or more water content can be analysed by the volumetric technique.
The Metrohm 774 automated oven processor has been developed for this automated task, with up to 35 samples at one time to boot.
The vial technique is applied, ie, the samples are no longer introduced into the oven by means of a sample boat, but in their own tightly sealed vials. The decisive advantages that this technique brings are numerous. Strictly reproducible analysis conditions for all samples, this is shown by the considerably improved precision of the results. Manual sample preparation is reduced to a minimum, just weigh, crimp and analyse.
Considerable savings in time and money.
Lower reagent costs, for example.
No contamination of the oven, consequently there is no carryover and memory effects.
Improved water release from the sample as the carrier gas does not just pass over the sample but directly through it.
Bound and unbound water can be determined independently.
Depending upon the samples water content, the analysis can be carried out volumetrically, for high levels, or coulometrically, for trace amounts.
