Monday, July 30, 2012

FAQ: Do I have to use a blank on my microplate when quantifying DNA at 260 nm?


Yes. When quantifying DNA using absorbance at 260 nm, a blank is required on the microplate. A blank is also required when using the cuvette port on the SPECTROstar Nano and when using the low volume LVis Plate. Quantifying DNA using absorbance at 260 nm requires the use of Beer’s law:

A=εbc


Where A is absorbance (no units), ε is the molar absorbtivity (L mol-1 cm-1), b is the path length of the sample (cm), and c is the concentration of the compound in solution (mol L-1).

Since most things in nature absorb light, including the plastic in the microplate and the DNA buffer (i.e. water or TE), a blank well with just these components should be subtracted from a well that also has DNA. After blank subtraction, only DNA will contribute to the “A” variable in Beer’s law above.

To learn more about quantifying DNA using a microplate (96- and 384-well), a cuvette, or the LVis Plate, please see  our Technical Application Note 001.

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