The water, which is very strongly bound in the plastic, is thermally driven off from the sample and transferred to the KF cell with a carrier gas stream
Most plastics dissolve only slowly or not at all in organic solvents.
This is why Metrohm recommends the heating method for such applications.
The water, which is very strongly bound in the plastic, is thermally driven off from the sample and transferred to the KF cell with a carrier gas stream.
Because of the very low water content the determination with the 831 KF Coulometer or 756 KF Coulometer is to be preferred.
The heating temperature should be optimized by applying a temperature gradient between 50-250C with the 774 oven sample processor.
This preliminary experiment shows that the water is released at low temperature (approx 90C), but also that at higher temperatures no side reactions take place.
For this reason a heating temperature of 220C was used to decrease the determination time.
For the determinations between 0.3 and 3g of sample were weighed in a vial and hermetically sealed with a septum cap.
Six determinations were run at 220C with the following result: water content 0.50% +/-0.01%.
