Photometry

A photometer is used in wastewater, drinking water, and environmental analysis to determine the concentration of dissolved substances.

For this purpose, specific reagents are added to the dissolved substance to convert it into a measurable colour. The colour is a result of the absorption of a certain proportion (wavelengths) of the white light, and hence the measuring is done at the wavelength with the largest absorption. Within a linear range the degree of light absorption can be translated into concentration.

Thus, photometers and test sets make up a system where components are matched optimally. Modern photometers provide method data for every test.

All necessary settings like wavelength, conversion factors, and blank value ( the own colour of a solution) are set automatically. When calibrating user defined methods or new reagents, the values for the test are measured, put in, and stored as a method.

Carl Stuart Limited supply the WTW range of Bench and Portable Photometers, and all necessary Reagent / Test kits for the determination of substances from Aluminium to Zinc.

Thermo-reactors are required for the determination of COD (Chemical Oxygen Demand), total nitrogen or total phosphorus. They ensure a complete digestion of the sample, as they maintain the necessary high reaction temperature throughout the whole of the defined period. The concentrations are then determined using a photometer.