Quantitative Protein Determination
Publication No. 12399
Biuret solution can be used with a spectrophotometer or colorimeter to quantitatively determine protein concentration.
Albumin, egg or bovine, 1 g
Biuret solution, 17.5 mL
Water, distilled, 605 mL
Balance, analytical, 1-mg or 0.1-mg
Flinn Scientific Spectrophotometer, or Flinn Calorimeter*
Test tubes, spectrophotometer, ½" x 4", or 13 x 100 mm, 7
*for use with Flinn’s computer interface system or TI-CBL data collection system
Biuret solution contains copper sulfate in a sodium hydroxide solution. It is corrosive to all body tissue, especially eyes. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Solutions should be neutralized using dilute hydrochloric acid solution and flushed down the drain with excess water according to Flinn Suggested Disposal Method #10.
Proteins are chains of amino acids connected by peptide bonds. Proteins and other smaller chains of amino acids are sometimes referred to as polypeptides. When biuret solution is added to a solution containing polypeptides, the copper ions in the solution react with the peptide bonds to produce a pinkish or purplish color.
Abramoff, P.; Thomson, R. G. Laboratory Outlines in Biology—V; W. H. Freeman: New York, 1991; pp 124–127.