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Wavelength-dependent measurement

The measurement of the absorption at different wavelengths can be used for pureness validation of the investigated substance. If the sample has no contamination, the ratio of the absorptions at different wavelengths stays the same provided that the substance absorbs at the investigated wavelength range. If the sample is polluted, the wavelength ratio changes on condition that the contamination also absorbs at the same wavelengths.

Field of application: Analysis of proteins and DNA

The bases purine, pyrimidine, adenine, and thymine are responsible for the UV-absorption characteristics of DNA with an absorption peak at 260 nm. For the pureness validation the absorption of the DNA sample is measured at 260 nm. For the determination of the concentration the Lambert-Beer law is used. Proteins are often a contamination in DNA-solutions. Due to their aromatic ring systems they have an absorption peak at 280 nm. The determination of the absorption ratio at 260 and 280 nm can be used for a pureness valuation of the DNA-solution. Using the Lambert-Beer law the absorption measurement at 280 nm can provide the protein concentration.

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