As a measure to distinguish between dissolved and
undissolved water-borne substances, the water
sample can be filtered through a simple paper filter.
Following the recommendations stated in the refe-
rence methods, membrane filters with a pore size of
0.45 µm are required for fine filtration.
3. Sample Preparation
Draw out the liquid to be
filtered with the syringe.
Screw the syringe tightly
into the front side of the
membrane-filter attachment.
Hold the syringe upright and
slowly depress the piston
upwards until the membrane-
filter is fully wetted free of air
bubbles.
Filter the contents of the
syringe into the intended glass
vessel.
Procedure for microfiltration
As a measure to ensure that a representative sample
can be taken in the presence of suspended matter in
the water sample in question, for certain parameters
(for example COD, total content of heavy metals) the
sample must be homogenized. This must be
carried out using a magnet stirrer (2 minutes at
700 – 900 rpm and taking the sample while stirring;
cf. DIN 38402 A30).
3.5 Homogenization
Water-borne substances can be present in the
sample for investigation in a variety of forms: as the
ion, bound more or less solidly in a complex, or as
a solid substance.
3.6 Decomposition
Ion
Complex
Solid substance
IX
Release 07/03
