Eppendorf G0.5 µPlate - Manual (Page 26)

Calculations
Eppendorf
® μPlate G0.5
English (EN)
26
9 Calculations
With each measurement, an additional measurement is performed automatically at a
reference wavelength of 340 nm to correct any absorbance value errors which may have
been caused by dirt on the outer surfaces of the Quartz wells.
9.1 Calculating the nucleic acid concentration
After the absorbance measurements of the nucleic acids have been performed in the
μPlate G0.5, the PlateReader AF2200 software and Excel automatically calculate the
nucleic acid concentration according to the Beer–Lambert law, including the reference
values.
A = ε * d * c
Generally, the absorbance A is defined in analytical chemistry as:
A
λ
= log
10
(I
0
/I) [OD],
whereby I is the intensity of transmitted light of a specified wavelength which passed
through a sample and I
0
is the intensity of the light before it entered the sample.
Absorbance measurements are frequently used in analytical chemistry because the
absorbance of a sample changes depending on the thickness of the sample and the
concentration of the absorbing species in the sample. Absorbance is a logarithmic
dimension and the unit is [A].
9.1.1 Example
An absorbance value of 1 OD equals a transmission of 10 %; an absorbance value of 2 OD
equals a transmission of 1 %, etc. As absorbance calculations are based on logarithmic
dimensions, calculations between absorbance sample values and absorbance blank values
are done by division instead of subtraction. Additional information can be found in the
literature on the Beer–Lambert law.
A Absorbance
ε Molar extinction coefficient (L mol -1 cm -1 )
D Distance (path length in cm)
c Concentration (mol L -1 )