Biuret Reagent

This was a very simple and very quick demonstration of Biuret reagent, which is a solution that turns from a royal blue to a royal purple in the presence of protein.

Biuret solution can be made in a number of different formulations. Some keep the copper solution and sodium hydroxide solutions separate until just before use, but this one—available from Liberty Scientific (wink, wink)—has the two mixed together. As with most things on my shelf, this has been sitting for quite a while (many, many years) and it still does the job fine.

What if YOU have some solutions needing qualitative protein testing? Well there are a few things you can do. The easiest by far is to pick up a bottle of Biuret Reagent from Liberty Scientific! Here’s a link to do that:

If you’re more of a do-it-yourselfer and you have the materials available, here’s a simple recipe:

• Prepare a solution of 0.23 grams copper(II) sulfate pentahydrate in 23 milliliters of water. Set this solution aside.
• Prepare a solution of 30.8 grams sodium hydroxide in 77 milliliters of water. A solution of sodium hydroxide this concentrated will get very warm. It is advisable to cool the mixing vessel in an ice-water bath.
• When both solutions are complete and at room temperature, add the copper sulfate solution to the sodium hydroxide solution at once.
• The color should change to a deep royal blue.

DISCLOSURE: The above link is NOT an affiliate link, but I own and operate Liberty Scientific LLC.