BUCHI SpeedDigester K-439 - Manual (Page 38)

6 Operation
38 K-439 Operation Manual, Version A
6 .7 .2 Peroxide digestion —preparing sample tubes
During the preparation process, handling with peroxides and other dangerous substances is inevi-
table. Peroxides are strong oxidants and can form explosives! All steps must be performed under safe
laboratory conditions.
! WARNING
Death or serious injuries by toxic and explosive peroxides.
Use only damage free sample tubes •
Exchange worn out or defective parts immediately •
Handle peroxides in a fume hood •
Do not bring peroxides into contact with highly combustible material •
Prerequisites
All sample tubes must be clean and free of damage. •
To achieve a reliable and reproducible digestion result the quality of sample material and the •
peroxide must be free of impurities and of adequate amount.
Filling of a sample tube
Take the sample tubes sequentially and weigh in sample material. •
Carefully(!) • add diluted sulfuric acid (e.g. 69%) of sufficient amount to the samples.
Carefully(!) • add peroxide (e.g. H
2
O
2
30%) of sufficient amount to the samples.
➡ The sample tubes can now be installed in a rack.
Note
Note down the sample weight and position to keep the probe processing and its analysis repro- •
ducible. All racks are marked on top with a "1" for the first sample position.
The rack(s) can be used as a temporary storage for empty tubes during the preparation process.
•
When adding the sulfuric acid and peroxide, rotate the tube to wash down any sticky sample •
material to the bottom and to coat the inside of the tube.