A colorimeter works by shining a particular colour (or wavelength) of light through a glass sample cuvette and measuring how much of that colour was absorbed by the water sample within the cuvette. The water sample will absorb more or less of the light depending on the reacted colour of the sample after the reagent has been added.
To ensure you get the best from your colorimeter it is worth ensuring you follow the best practise guidelines laid out below:-
1. Keep your glass cuvettes clean and free of scratches. If they are dirty or scratched then some of the light that would have passed through your water sample will be deflected and an incorrect reading can be the result.
2. Do not shake the cuvette after adding the reagent - just invert it gently a couple of times. If you shake it you can create a series of tiny air bubbles which disrupt the light beam as well as causing the undissolved reagent to be in suspension and in the way of the light beam.
3. Wipe dry the cuvette before placing it into the sample chamber of the instrument. Water droplets on the outsite of the glass cuvette interfere with the light beam thus giving a potential false result.
4. Don't take the reading too soon or too late. For each of the colorimeter parameters there is a specific reagent which itself has a very specific reaction time before the sample is ready to read. If you take the reading too early not enough colour may have developed, too late and too much colour may have developed - either way, your reading will not be accurate.
