Biuret's test

Biuret's solution is a blue liquid that contains copper sulfate (CuSO₄) and sodium hydroxide (NaOH). Copper sulfate actively binds to the peptide bonds in proteins, forming a structure that transmits a violet color in an alkaline environment. The sodium hydroxide provides the alkaline environment.

Figure 1: (-) is negative result; (+) is positive result.

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• Food biochemistry test