The Bradford assay uses the spectral properties of Coomassie Brilliant Blue G-250 to estimate the amount of protein in a solution. A protein sample is added to a solution of the dye in phosphoric acid and ethanol. Under the acid conditions the dye is normally a brownish colour but on binding to the protein the blue form of the dye is produced. The optical absorbance of the solution is measured at a wavelength of 595 nm. The dye is notable due to its high level of sensitivity, 5 μg of protein is enough to distinguish the difference. However, among the disadvantages of the method is its variability of color development with different proteins: the absorbance change per unit mass of proteins varies with the type of the protein.