BUCHI DuMaster D-480 - Manual (Page 126)

Operation Manual D-480 ©BÜCH Labortechnik AG
7 - Using the instrument 126
Sample preparation instructions
Samples with potential risks
Various sample substances can pose a risk to the user during the analysis:
 Contact with the substances may lead to chemical burns or poisoning.
 Combustion analysis of larger quantities of the substance may lead to explosions.
These sample substances include:
 Aggressive chemicals such as acids or alkaline solutions
 Organic solvents
 Explosives
 Substances that develop toxic or explosive gas mixtures.
Users are obliged to protect themselves prior to contact with hazardous substances and to reduce the
quantity of the substance to a safe amount. Users are also obliged to observe the safety instructions
of the chemical manufacturer on the label of the bottle or in the safety data sheets. The safety data
sheets contain risk information about a chemical in the R-Phrases and safety information in the S-
Phrases.
Sampling and homogenization
Refer to the relevant literature concerning the problem of sampling and homogenization.
Sample crushing and drying
When crushing and drying samples you may lose highly volatile constituents. Also, the sample may
get contaminated with foreign substances.
What influences analysis results?
The following influences analysis results:
 In nitrogen analysis, inclusions of air in the samples influence analysis results. Inclusions of air
must therefore be avoided.
 The moisture content of samples influences the analysis result through its weight proportion.
Determining sample weight
What is optimal sample weight?
Optimal sample weight is determined by the following
 the N content of the corresponding sample to be measured,
 the homogeneity,
 the valid calibration,
 the combustion behavior of the sample,
 the oxygen requirement,
 the pressure arising during combustion,
 and that combustion of the sample is limited in time and controllable in terms of pressure.
Determining sample weight with known substances
The following rule of thumb applies to determine the sample weight of known substances:
 The sample weight should be as high as necessary and as low as possible.