Metrohm 874 USB Oven Sample Processor - Manual (Page 44)

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36 ￭￭￭￭￭￭￭￭ 874 Oven Sample Processor
4 Processing a sample series
Moisture determinations according to the heating method require the
conditioning of the entire tubing system and of the KF titration cell before
a determination can be carried out. Because the sample vials and the sep-
tum seals may contain small amounts of moisture, three to five blank
value determinations must be carried out with sealed, empty vessels. For
conditioning, blank value and sample determinations, example methods
for tiamo
™ are to be found in the installation directory of the software.
Preparing
Weigh solid or liquid samples into sample vials and seal these securely
with the septum crimping tongs. We recommend the use of the
6.2419.007 sample vial with the 6.1448.057 septum seals. The silicone
septum of the aluminum cap is resistant to temperatures of up to 250 °C
and has shown iself to be exceptionally reliable. In addition to the sample
vials, you will also require for a sample series an empty, tightly sealed vial
as a conditioning vessel, in addition to three to five vials (which are also
empty and tightly sealed) as blank samples.
Place an empty, sealed vial as conditioning vessel at the Cond. Pos.
position on the sample rack of the 874 Oven Sample Processor. The
empty blank samples are placed on Positions 1 to 3 (or 5) on the sam-
ple rack. Place the vials filled with samples on the following positions.
In the sample table of tiamo ™ one line must be filled out with the asso-
ciated method and sample data for each vial on the sample rack. Observe
in this connection the explanations contained in the Application note for
the individual methods. The vials must be processed in the correct
sequence. It is for this reason that the sample table must be filled out as
follows:
￭ Line 1: conditioning method
￭ Lines 2 to 4 (6, resp.): method for blank value determination
￭ Lines 5 (7, resp.) to x: method for water content determination
Observe the following during conditioning:
￭ In the KF titration cell, the shaft of the heating tube should not be
immersed in the working medium.
￭ Align the tip of the heating tube against the vessel wall.
￭ Set the stirring rate to high. The carrier gas should emerge from the tip
of the heating tube into the working medium as tiny bubbles and be
spun there forcefully. It is advantageous for air bubbles to be stirred
into the working medium and forcefully broken up in the process. The
air in the KF titration cell must also be dried.