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Concentration from OD

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Spectroscopy (chemistry) index
Concentration from OD diagram
Assuming that no other absorbing species are present, a sample concentration can be determined from a measurement of OD at a wavelength where the substance has a know absorption coefficient (epsilon or cross-section, and usually at a maximum).
Absorption coefficient
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The spectral determination of concentration is pivotal to many analyses, particularly in analytical chemistry and biology. The reverse transformation of known concentration to give the absorption coefficient (required to calibrate for concentration analyses) is provided in another calc.
The absorption coefficient here may be entered e.g. as the popular ε or the cross-section σ in any of several units.