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Photometric analysis is a very powerful technique,
providing accurate analysis of a wide range
of critical swimming pool, spa, hydrotherapy
and hot tub parameters.
Palintest has focused on simplifying the test
methods and equipment used for this technique
but there are still a number of ways to ensure the
results you generate are as accurate as possible:
1 Always use genuine Palintest reagents when
using the programmed test methods. Each
parameter has a unique calibration which
has been generated using Palintest reagents.
Alternative reagents may follow the same
general methodology but can differ
substantially in formulation and colour
generated thereby rendering the calibration
and results inaccurate.
2 Always correct for the blank value - any
inherent colour in the sample (which may
not be visible to the naked eye) will offset
the result if the blank step is omitted.
If the sample colour is too intense for the
photometer to blank use dilution with
deionised water to reduce the intensity.
Remember to dilute the sample to the
same extent for analysis.
3 Always respect the reaction time specified
within the instructions. Some methods
produce instant colour whereas others require
a reaction time to reach full development.
Taking a reading before the reaction time
has elapsed may lead to low results.
4 The presence of solids, either large or in the form
of turbidity, can adversely affect the quality of
results by preventing incident light from reaching
the detector. The blanking step can reduce the
impact of turbidity interference but large solid
particles must be removed prior to analysis.
Solids can be removed by filtration prior to
analysis or, if the solids are settleable and will not
lie in the optical path, allowing them to settle
in the photometer cuvette can be acceptable.
Appendix 1 - Photometric Testing Hints and Tips
5 Calibration curves relate transmission/absorbance
to concentration to provide result data but
not all calibration ranges are linear. Frequently
at higher concentrations the curve 'flattens'
leading to higher potential variability in
results. If greater accuracy is required than
can be achieved on neat samples then dilution
can be used to improve performance.
6 Ensure the photometer cuvette is clean,
has no droplets on the outside and is not
excessively scratched. Good technique is to
wipe the outside surface of the cuvette
prior to inserting into the optical chamber to
prevent contamination of the optical system.
7 Always use good quality, genuine Palintest
cuvettes. Use the orientation mark to ensure
repeatable positioning of the cuvette.
8 Maintain the cleanliness of the optical chamber
by only inserting clean cuvettes. If the chamber
becomes fouled or sample is spilled the base
can be removed for cleaning access. Clean the
optical chamber with a soft cloth. Do not use
abrasive chemicals or scouring agents.
9 Always use the light cap provided to prevent
ambient light affecting results. This is especially
relevant when operating in strong sunlight or
other light conditions.
10 Ensure your Pooltest 25 is operating effectively
by using Palintest Check Standards and the
Check Standard Mode (see Section
9 Calibration/Validation) and having the
photometer serviced and calibrated at regular
intervals. Calibration is recommended at 12
month intervals for normal usage and can be
provided by your local Palintest distributor.
The Pooltest 25 features self-diagnostic software
and hardware to optimise performance and
battery life. The Info panel indicates the status of
the Pooltest 25 and any specific fault conditions
are defined and displayed on screen.
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