One of the most common methods for nucleic acid detection is the measurement of solution absorbance at 260nm (A260) due to the fact that nucleic acids have an absorption maximum at this UV wavelength. Although a relatively simple and time-honored method, A260 suffers from low sensitivity and interference from nucleotides and single-stranded nucleic acids. Furthermore, compounds commonly used in the preparation of nucleic acids absorb at 260nm leading to abnormally high quantitation levels.

However, these interference and preparation compounds also absorb at 280nm leading to the calculation of DNA purity by performing ratio absorbance measurements at A260/ A280.