The properties of nitrations to absorb UV light of certain wavelengths, is used for nitrate measuring. The UV light of a pulsed flash lamp shines through a flow measuring cuvette is then partially absorbed by the nitrations in the sample flow. The intensity of the weakened light is then measured at a measuring and reference wavelength and electronically evaluated.

The applied 4-beam measuring method ensure a high degree of longterm stability and absolute accuracy; interfering background influences are efficiently compensated.