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Molar absorptivity



(1) A measure of how strongly a chemical species absorbs light at a particular wavelength. It is often expressed in units of cm-1M-1.

(2) A fundamental unit in spectrophotometry.


It is symbolized by ε in Beer-Lambert law, A = εcl, where A is the absorbance of the sample, l is the pathlength (usually in centimeter), and c is the concentration of the of absorbing species in the material (moles per liter).

Symbol: ε


See also: Beer-Lambert law

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beers law concentration calculation

... the number of Trp and Tyr residues, 3 and 6, so I have calculated the molar absorptivity as 3*5600+6*1420= 25320 M^-1cm^-1. Is this the correct units for this value? The ...

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by protchem12
Thu Jan 12, 2012 5:24 pm
Forum: Molecular Biology
Topic: beers law concentration calculation
Replies: 8
Views: 7137

Re: Beer Lambert Law

... I didn't check the extinction coefficient (now preferably called the molar absorptivity) of NADH. I'll take your word for it that it is 6.22E3 A/ M cm. What you haven't ...

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by blcr11
Thu Mar 05, 2009 2:42 pm
Forum: Molecular Biology
Topic: Beer Lambert Law
Replies: 1
Views: 8028

Re: beer-lambert law

I expect the units of the molar absorptivity to be M^-1 * cm^-1. This will give you an answer in molarity. You'll need to convert to micromoles. ...

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by jonmoulton
Fri Feb 27, 2009 4:53 pm
Forum: General Discussion
Topic: beer-lambert law
Replies: 4
Views: 8921

Re: beer lambert law

The stated coefficient is in the wrong units to be a molar absorptivity (or molar extinction coefficient). That would be in units of A per M (per 1 cm pathlength, ...

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by blcr11
Tue Oct 07, 2008 4:48 pm
Forum: Molecular Biology
Topic: beer lambert law
Replies: 3
Views: 11603

spectrum of riboflavin

... to emperically determine at least the absorption spectrum, if not the molar absorptivities, of riboflavin, DNA and protein by taking absorption ... used to estimate concentrations of material in solution if you know the absorptivity at the particular wavelength. There are "standard" ...

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by blcr11
Sat Apr 14, 2007 4:01 pm
Forum: Cell Biology
Topic: spectrum of riboflavin
Replies: 5
Views: 7718
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