DNA purity and quantity measurement | by Absorbence and Gel electrophoresis |

Measurement of purity and DNA concentration

DNA concentrations can be accurately measured by UV absorbance spectrometry. The amount of UV radiation absorbed by a solution of DNA is directly proportional to the amount of DNA sample. Usually absorbance is measured at 260 nm, at which wave length an absorbance of 1.0 corresponds to 50 µg of double-stranded DNA per ml. UV absorbance can also be used to check the purity of a DNA preparation. With a pure sample of DNA the ratio of the absorbancies at 260 nm and 280 nm (A260/A280) is 1.8. Ratios of less than 1.8 indicate that the preparation is contaminated, either with protein or with phenol.

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