Taking A Sample - palintest Photometer 7500 Operation Manual

3. Taking a Sample

The first critical step in any analysis is taking a representative
sample. When selecting a sample point a number of care
points are recommended as follows:

Ensure the sample point is safe to access and follow
all relevant/required precautions.

When sampling from a tap or outlet, remove any
attachment and clean the tap/outlet with a dry cloth
before allowing the tap/outlet to run for 1 minute prior
to sample collection.

When sampling from a river or stream take the
sample as near as possible to the main flow and not
too close to the edge where the water may be still and
unrepresentative of the sample as a whole.

Rinse any sample container repeatedly with the
sample to prevent any cross contamination from
previous samples.

Once collected the sample must be processed
immediately or as quickly as possible, especially for
highly reactive species such as chlorine for example.
The use of a portable field test kit makes this
possible. However if the delay between sample
collection and analysis is likely to be several hours
chill the sample to preserve and prevent potential
microbiological growth.

Samples containing solid particles can interfere with
photometric analysis. Either allow solids to settle and
decant the clear liquid or filter the sample prior to
analysis.
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