Absorbance measurements are used for calculating concentrations of carotenoids such as Fucoxanthin, a dominant pigment in diatoms, or Peridinin, a diagnostic pigment of dinoflagellates. Absorbances are also used for calculating concentrations of fluorescing pigments such as chlorophyll a, b, or c. Other absorbance applications include the determination of chemicals/nutrients in water systems (i.e.Nitrate, Silicate, Phosphate, Ammonium, etc).
Absorbance is a measurement of light absorption by solid, liquid or gas. The electrons of the atoms in the absorbing substance reduce the amount of light being passed through that material. As the quantity of atoms increases so does the reduction of photons being transmitted. Beer's Law states that the amount of light transmitted by the sample is proportional to the concentration of the absorbing species and the path length traveled by the light.