The 874 Oven Sample Processor is used for thermal sample-preparation in Karl Fischer titration.
It is suitable for samples that only release their moisture at higher temperature, for hardly soluble samples or samples that undergo side-reactions with the KF reagent.
If the 874 USB Oven Sample Processor is connected to a PC via the USB port, the instrument is recognised automatically.
Running a temperature gradient can define the optimal oven temperature for every sample.
Metrohm's 800 Dosinos can be attached to one of the sample changer's MSB ports.
A Dosino and dosing unit allow automatic reagent exchange.
A sample changer can drive out the moisture contained in liquid or solid samples.
For the oven method, a sample is weighed in a sample vial, tightly closed and placed on the rack.
The sample is then heated up in the oven and the moisture is evaporated.
A double hollow needle pierces the septum and a dry carrier gas-flow transports the moisture into the titration cell, where the Karl Fischer titration takes place.
A big advantage of the oven method is the fact that the sample itself is not introduced into the titration vessel.
Contamination of the oven and the titration cell as well as side-reactions and matrix effects are eliminated.
The optimal oven temperature is important if unknown samples are to be analysed.
The oven temperature should be chosen as high as possible to ensure a fast evaporation of the moisture and a quick transport into the titration cell.
But the sample should not start to decompose, as the products of decomposition would falsify the results.
The 874 USB Oven Sample Processor allows the unknown sample to be subjected to a temperature gradient.
The optimal oven temperature can then be defined based on the resulting heating curve.
Besides a stirrer, Dosinos and dosing units can also be attached to the 874.
This makes it possible to aspirate spent reagent and automatically add fresh solvent.
There is no need to open the cell, which means no additional moisture enters it.
This shortens conditioning and saves time.
The Dosino can also be used to add auxiliary solutions such as buffers.
