Bio-rad SmartSpec Plus Spectrophotometer User Manual download pdf (Page 9)

The Lambert-Beer’s law identifies the relation between sample concentration and the

intensity of transmitted light. Absorbances and % transmittances are defined by the follow-

ing equations:

% Transmittance (%T)

%T = I

* 100 = 10

-εcl

* 100

Absorbance or optical density (A or O.D.)

A = log

1/T = log

= log

εcl

= εcl

Where I

= Intensity of incident light

= Intensity of transmitted light

ε = Molar extinction coefficient (liter/mole/cm)

c = Sample concentration (mol/liter)

l = Optical pathlength

Fig. 6. Lambert-Beer's law.

A = log 1/T A = εcl

Fig. 7. Relationship between Transmittance and Concentration and Absorbance and

Concentration.

Sample concentration C

Incident light l

Transmitted light l

= l

εε

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 57 58

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Bio-rad SmartSpec Plus Spectrophotometer User Manual Page 9