Purpose
The MA moisture analyzer can be used
for quick and reliable deter mination
of the moisture content of materials of
liquid, pasty and solid substances using
the thermogravimetric method.
19
Basis of Moisture Analysis
Material
The moisture of a material is often
mistakenly equated to its water content.
In fact, the moisture of a material
includes all of the volatile components
which are emitted when the sample
is heated, irrespective of the type of
material. Among such volatile substanc-
es are:
– water
– fats
– oils
– alcohols
– organic solvents
– flavorings
– volatile components, products
of decomposition (when a sample
is overheated)
There are many methods for deter-
mining the moisture content of a sub-
stance. These methods can be divided
into two categories:
When absolute methods are used, the
moisture content is determined directly
(for example, as a weight loss registered
during the drying routine). These
methods include oven drying, infrared
drying and microwave drying.
All three of these methods are thermo-
gravimetric.
When deductive methods are used, the
moisture content is determined indi-
rectly. A physical property related to the
moisture in the substance is measured
(e.g., absorption of electromag netic
rays). These methods include Karl-
Fischer titration, infrared spectroscopy,
microwave spectroscopy, etc.
Thermogravimetry is the process of
determining the loss of mass that occurs
when a substance is heated.
In this process, the sample is weighed
before and after being heated, and the
difference between the two weights
determined is calculated.
In a conventional drying oven,
circulating hot air warms the sample
from the outside inwards. Efficiency
is lost during drying because as
the moisture evaporates, it cools the
sample surface.
By contrast, infrared rays (IR rays)
penetrate a sample without being
impeded. Having reached the interior
of a sample, they are converted into
heat energy.
IR-Strahlung
Substanz
Wärmeenergie
IR rays
thermal energy
substance
To Next Page
Loading...
