6.3 Test kits
The majority of appropriate test kits involve colorimetric methods. They come in two main
formats, those using visual comparators and those using portable or bench top spectrometers.
Generally, the use of visual comparators is not recommended, as these systems are very
dependent on the operator and environmental conditions. They often lack the accuracy
required for assessing regulatory permits. If they are employed the users must demonstrate
that they are fit for purpose.
Test kit methods using spectrometers have increased in sophistication and quality in recent
years, and many are based on standard laboratory methods. Traceability of the data can be
achieved due to electronic result storage capabilities.
Test kits offer some advantages as the methods may benefit from reagents being pre-
packaged, ease and convenience of use, and built in calibration routines. However, they
should undergo a full evaluation before use, ensuring appropriate performance characteristics
and matrix suitability, and be treated the same as a standard method in terms of
documentation and QA/QC procedures.
Test kits are employed for many determinands, COD, ammonia, phosphate and iron included.
Comprehensive guidance to test kit usage can be found in reference 19.