Method for measuring absorption which allows eliminating interferences by alternately detecting absorbance at two different wavelengths.
When measuring absorption in the continuous stream, various interferences can occur which can be countered by adapted methods provided by SIGRIST: the differential measuring method compensates the effects of the loss of reflection at the flow cell’s windows, of absorption of the solvent or of window contamination. Turbidity compensation allows to compensate not only these interferences but also changes in the liquid to be measured itself. Thus, for example, a change in turbidity, air bubbles or other absorbing substances do not have any influence on the reading.
To achieve this the same sample is alternately measured with the light of two different wavelengths. The measuring wavelength has to lie at a position of the spectrum at which the substance to be determined absorbs and the compensation wavelength at a position at which it does not absorb. Colour measurement (beer); Colour measurement (water)