The amount of light that is absorbed by a sample can be expressed as absorbance. Normally, different molecules absorb radiation of different wavelengths.
An absorption spectrum is the result of electronic, vibrational and rotational transitions and will show a number of absorption bands corresponding to structural groups within the molecule. It is this selective absorption of radiation, which forms the basis for qualitative and quantitative absorbance spectroscopy. 

In practical terms an absorption spectrum is characterized by two parameters, the maximum position (λmax) and the molar extinction (ε) calculated in general at λmax. The relation between ε, sample concentration (c), and thickness (l) of the absorbing medium is characterized by the Beer-Lambert law: the concentration of a substance in solution is directly proportional to the 'absorbance ', A, of the solution:

Absorbance A = constant x concentration x cell length

While passing through the sample, light is partly absorbed, and the spectrometer will record the nonabsorbed or transmitted light. The relation between the absorbed and transmitted light is expressed by the relation presented bellow, 

A = -log T = εcl

The application fields for this technique are numerous and can cover from chemistry, life sciences, and environment to petrochemical industry or cosmetics.

Sarspec offers different configurations for abasorbance measurements. The Absorbance SPEC Packs are available with different sampling accessories including cuvettes, flow cells or transmittance probes. 

For applications where temperature control and stirring are relevant the Peltier Cuvette Holder CH-QPOD2E is a great flexible option.