Buchi SpeedDigester K-439, Operation Manual, Page: 38 / 68

6 Operation
38
K-439
Operation Manual, Version B
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.