What is a biuret solution?

A biuret solution is a liquid mixture of potassium hydroxide and copper sulfate used to detect proteins and peptides in human urine. In this alkaline solution, the copper sulfate ions react with the peptide bonds of proteins to turn the blue solution violet if protein is present.

It is common for biuret tests to detect some protein in human urine, but when the result of several tests is consistently beyond normal levels, it indicates a potential kidney problem. Excess protein can also result from conditions such as diabetes, heart disease, high blood pressure, and preeclampsia and eclampsia in pregnant women.