Question

Why is NaOH added first in the biuret test

Answer 1

Answer:

The protein is dissolved by the NaOH. The copper salts will then react with the protein. When you use so much NaOH, the copper hydroxide becomes the dominant reaction, and the purple color is lost. If you use commercially available Biuret, first dissolve the food in NaOH to get a deeper color.

hope this helps

Answer 2

Answer:

to raise the pH of the solution to alkaline levels.