Ninhydrin

Ninhydrin is a chemical reagent widely used in biochemistry and forensic science for the detection of amino acids, peptides, and proteins. It reacts with free amine groups to produce a deep purple or blue color known as Ruhemann’s purple.

🏭⚗️ Production
Ninhydrin is synthesized industrially through oxidation of hydrindantin or related compounds. In the laboratory, it is typically available as a white to pale yellow crystalline powder and is soluble in solvents like ethanol, acetone, or water. For most applications, a 0.1–1% solution in a volatile organic solvent is used.

🔬 Properties
Ninhydrin is a strong oxidizing agent that reacts specifically with primary and secondary amines. Upon heating, it reacts with amino acids to form a chromogenic complex that absorbs strongly in the visible spectrum. The resulting color is typically deep purple, though some amino acids produce yellow or orange shades. The compound is light-sensitive and should be stored in airtight containers away from heat and light.

🧪 Applications
• Biochemistry: Used for detecting and quantifying amino acids and proteins in chromatography and electrophoresis.
• Forensic science: Commonly applied to detect fingerprints on porous surfaces like paper by reacting with amino acids in sweat residues.
• Analytical chemistry: Serves as a sensitive reagent in thin-layer chromatography (TLC) to visualize amino acids.
• Research & teaching: Used in lab exercises to demonstrate protein detection and to teach chemical principles of amine reactivity.
• Clinical labs: Occasionally used in urine or plasma tests to detect amino acid metabolism disorders.