Biuret reagent
The Biuret reagent is made of sodium hydroxide (NaOH) and hydrated copper(II) sulfate, together with potassium sodium tartrate
Uses.
A tri- or tetra-dentate chelation with the peptide nitrogen produces the characteristic color. This is found with dipeptides. 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.