Metrohm 860 KF Thermoprep - Manual (Page 41)

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860 KF Thermoprep ￭￭￭￭￭￭￭￭ 33
Note
The signal drift on the KF titrator should be less than 20 µg/min (or
µL/min) and remain stable for at least 2 minutes before the blank value
determination can be started.
5.2 Determining the blank value
Because the surface of the sample vessels and the air enclosed in the ves-
sel could contain moisture, it is imperative that three to five blank value
determinations be carried out. One determination with an empty, tightly
sealed sample vessel is carried out in each case. The result is calculated as
the quantity of water expelled from the sample vessel. The titration
parameters used for a regular sample must also be applied to blank value
determinations. Select a relative stop drift of 5 µg/min (or µL/min) as the
stop criterion.
Preparing the blank
The system should already be conditioned. A conditioning vessel must be
in the oven at this stage and the needle must already be inserted.
1 Seal three to five sample vessels tightly with the crimping tongs.
2 Check that the oven temperature and the gas flow rate correspond
to the values which have been set.
3 Wait until the working medium in the KF titration vessel has been
conditioned and the signal drift is stable.
Starting the blank value determination
1 Start the determination by pressing the [Start] key on the KF titrator.
2 Use both hands to move the guide head of the 860 KF Thermoprep
upward while pressing the fixing lever.
Refer to the illustrations on pages 31 ff.
3 Remove the conditioning vessel from the oven with the crimping
tongs.