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This colorimetric chemical test used to detect the peptide bond using the Biuret reagent is called the Biuret test. It is also called Piotrowski’s reaction after the name of the Polish physiologist Gustaw Piotrowski who observed this phenomenon in 1857 and used it to detect proteins in samples.
The biuret test is a colorimetric test that helps detect specific proteins or peptide bonds in given analytes. It is followed by spectrophotometry for quantification. The test requires the use of a biuret reagent.
The reagent is commonly used in the biuret protein assay, a colorimetric test used to determine protein concentration by UV/VIS spectroscopy at wavelength 540 nm. High sensitivity variants of the biuret test.
The Biuret Test for Protein is based on the principle that copper ions in the Biuret reagent react with peptide bonds to form a violet-coloured complex. The Biuret reagent contains sodium hydroxide, copper sulphate, and potassium sodium tartrate.
The biuret test can be used to assess the concentration of proteins because peptide bonds occur with the same frequency per amino acid in the peptide. The intensity of the color and hence the absorption at 540 nm, is directly proportional to the protein concentration.
To test for the presence of Protein in a given sample use the Biuret test. To 2ml of test solution add an equal volume of biuret solution. A blue ring forms at the surface of the solution, which disappears on shaking, and the solution turns lilac-purple, indicating protein.
Biuret test is used to detect proteins in the sample. The peptide bonds of protein form a purple violet complex upon reaction with CuSO4 in alkali condition. The intensity of the complex is directly proportional to the number of the peptide bond in the protein sample.