BUCHI Wet Digester B-440 - Manual (Page 26)

6 Operation
26 B-440 Operation Manual, Version D
After the application:
Use the handle to safely lift the glass hood. s
Use the crucible tongs to remove the crucibles. The crucibles can be slippery! Ensure safe grip s
before taking out the crucible of the ceramic plate completely!
Place hot crucibles on a acid- and fireproof surface only. s
Switch "OFF" the Wet Digester and the Scrubber. s
Clean all accessories that have been in use. s
๗ Optional: Dispose of the filling of the condensate trap if the activated charcoal is exhausted (e.g.
shows signs of a high moisture content).
! Caution
Risk of moderate chemical burns by splashing acid or peroxide drops.
Carefully unplug the suction hose connectors s
Wipe off any liquid drops from the suction hose(s) and the condensate trap s
Wear safety goggles s
Wear safety gloves s
6.3 Optimization principle for ashing programs
The various molecule structures make it impossible to develop a general-purpose wet or dry ashing
procedure for all substances. Each substance has its own ashing kinetics and therefore its own profile
of the decomposition temperature.
Observe the following rules to optimize a wet ashing program
Added acids or peroxides at wet ashing tend to boil over at high start-up temperatures. Thus, carbon-
ization often requires gradually heating stages.
If the sample contains water, evaporate it during the first step by heating the sample at approx. s
120°C for a sufficient time.
After carbonization, the heating can be increased to up to 600 °C for ashing. Intermediate tempera- s
ture steps might be necessary at different ashing-reaction stages.
Note
The temperature inside the crucible will be slightly lower than the selected heating temperature. The
ഉ5CFUXFFOIFBUJOHBOEDSVDJCMFEFQFOETPONBOZGBDUPSTTVDIBTXBMMUIJDLOFTTPGUIFDSVDJCMFT
BOEUIFEJHFTUJOHTBNQMFT
NOTE
If the sample is heated to too high temperature too quickly, it may ignite or be propelled out of the
crucible.