Laboratory medicine

Laboratory medicine

Friday, April 15, 2016

What is colorimetry: Principle and applications

When light is passed through a coloured solution, certain wavelengths are selectively absorbed giving a plot of the absorption spectrum of the compound in solution. The wavelength at which maximum absorption is called the absorption maximum (λmax) of that compound. The light that is not absorbed is transmitted through the solution and gives the solution its colour.

Photometric instruments measure transmittance, which is defined as follows:

                                 Intensity of the emergent (or transmitted) light         Ie
Transmittance (T)= ---------------------------------------------------------------- = ------
                                               Intensity of the incident light                         Io

Transmittance is usually expressed on a range of 0 to 100%.

Colorimetry priniciple

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