A small part of the IR rays is reflected
from the surface of the substance. The
quantity of reflected IR rays depends to
a great extent on whether the substance
is light or dark-colored.
Dark Substance
Light Substance
Low Reflection
High Reflection
How the rays penetrate the sample
depends on the sample’s degree of
light-transmitting capacity. If the
degree of light-transmitting capacity is
low, the rays can penetrate only the
uppermost layers of the sample. The
heat conductivity of the sample dictates
the degree to which the heat can be
transmitted to the underlying layers.
The higher the conductivity, the faster
and more uniformly the substance is
heated.
The substance should be applied to the
sample pan in a thin, even layer. A
height of approximately 2 – 5 mm for
5 – 15 g substance weight has proved
to be ideal. Otherwise, the sample will
not be dried completely or the analysis
time will be unnecessary extended, a
crust/skin will form on the surface of
the sample or the sample will scorch,
and the analysis results obtained will
not be reproducible, and therefore
cannot be used.
Incorrect Application of a Sample
When preparing a substance for analy-
sis, you should use methods that do not
generate heat so that the sample does
not lose moisture before it is analyzed.
Perform initial analysis of a new sub-
stance to test how the IR rays are
absorbed by the sample and converted
into heat. A printout of the intermedi-
ate values of the drying process (see
page 25) provides you with this infor-
mation at an early stage.
Experience has shown that the tempera-
ture setting selected for infrared drying
is usually lower than the temperature
setting used when working with a dry-
ing oven.
In many cases, the fully automatic shut-
off mode will meet your requirements.
If the final result is higher or lower than
expected, try varying the temperature
setting before resorting to a different
shutoff parameter.
When analyzing the samples that lose
their moisture only very slowly or when
operating a cold moisture analyzer,
the fully automatic mode may end the
drying routine too early, if it does not
detect any analyzable progress in the
drying routine under these conditions.
In this case, preheat the moisture ana-
lyzer for 2–3 minutes before starting
the drying routine, or select a different
shutoff parameter.
The Sartorius Moisture Analyzer
Applications Guide will provide you
with important information on the
use of your moisture analyzer.
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