Metrohm 874 USB Oven Sample Processor Manuel d'utilisateur télécharger pdf (Page 44)

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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.

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Metrohm 874 USB Oven Sample Processor Manuel d'utilisateur Page 44