Grinding Balls - Sartorius Mikro-Dismembrator U Bedienungsanleitung

1.2.3 Grinding Balls

The characteristics of the grinding balls, such as their
size, abrasiveness and (specific) weight, will essentially
determine the final fineness, homogeneity or
compactness of the treated sample and the time
required for disintegration. Furthermore suitable
grinding balls are selected according to the material
characteristics of the raw sample (hardness, compactness
or toughness, chemical composition, etc.), the type of
assay to be applied afterwards and the required fineness,
homogeneity or compactness of treated sample. Process
materials like silica sand, dispergents or buffers can be
added to improve disintegration and homogenization of
the sample.
Available grinding balls and process materials are, for
instance:
1. Glass beads of Ø in the range of about 0.10 ... 1 mm.
2. Balls made of quartz agate (Brazilian agate), with a
diameter of about 10 mm at a weight of 2 g.
3. PTFE balls (PTFE coated steel balls with steel core), with
a diameter of about 10 mm; weight 2 g.
4. Stainless steel balls, Ø about 3 ... 10 mm, weight range
within 0.11 ... 4.1 g.
5. Balls made of tungsten carbide, Ø about 1 ... 9 mm,
weight range within 0.07 ... 5.63g.
•
Please refer to more detailed information about the
available grinding balls and process materials in
section 4. Specific data (material characteristics,
chemical composition, etc.) are included in the
supplement.
The grinding balls and process materials must not affect
the subsequent analysis of the samples. For instance,
rubbed-off material of the grinding balls, of the shaking
flasks or of the process materials, respectively, must not
distort the results of trace element analysis. Therefore
some general recommendations for use of grinding balls
and process materials should be heeded:
•
When soft materials are to be treated and prepared for
trace element analysis, we recommend to use PTFE balls
with steel core (made of high-purity PTFE) or balls made
of quartz agate (Brazilian agate). The latter show low
abrasion and can be used for abrasive samples.
•
For most of the common applications, like
disintegration of semi-solid or solid samples, the
stainless steel balls may suffice.
•
Tungsten carbide balls, which offer a high specific
weight, can be recommended for fast and efficient
disruption of solid (or highly abrasive) samples.
Except for trace element analysis, glass beads or silica
sand can be added to the samples to improve the
treatment. Furthermore, Tris-buffer can be added to the
shaking flask. Tough materials (rubber, plastics, etc.) can
be frozen in liquid nitrogen to optimize disintegration.
Likewise biological materials, such as tissue samples at
yeast cells, can be quickly disrupted in the Mikro-
Dismemrator U after they have been frozen in liquid
nitrogen.
Disintegrated particles tend to conglomerate due to
their adhesion interaction. This can be prevented by
adding a dispersion material or liquid to the sample
and wet milling.
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