Sartorius MA150 Operating Instructions Manual page 20

A small percentage of IR rays is
reflected by the substance. The quantity
of reflected IR rays depends to a great
extent on whether the substance is light
or dark in color.
dark substance light substance
low reflection high reflection
How the rays penetrate the sample
depends on the light-transmitting
capacity of the sample. If the light-
transmitting capacity is low, rays can
only penetrate 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 unnecessarily 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
20
When preparing substances for
measurement, do not use processes that
generate heat, as the heat generated
may result in a loss of moisture prior
to the measurement.
Perform initial analysis of a new
substance to test how the IR rays are
absorbed by the sample and converted
into heat. A printout of the inter-
mediate values of the drying process
provides you with this information
at an early stage.
Experience has shown that the tem-
perature setting selected for infrared
drying is usually lower than the
temperature setting used when working
with a drying oven.
In many cases, the fully automatic
shutoff mode will meet your require-
ments. 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 since no ana-
lyzable progress in the drying routine
can be detected. In this case, preheat
the moisture analyzer for 2–3 minutes
before starting the drying routine, or
select a different shutoff parameter.
The Sartorius Moisture Analyzer
Applications Guide provides you with
important information on the use of
your moisture analyzer.