Ninhydrin Test Protocols

Ninhydrin is a chemical substance mostly used in biochemical laboratories as a reagent for amino acids, which are small molecules that form proteins, as well as in forensics to detect finger prints and faint blood stains, according to the Australian Federal Police. Ninhydrin protocols include the ninhydrin test for amino acids, fingerprints revelation and ninhydrin test for peptide synthesis.

Ninhydrin Test for Amino Acids

• Ninhydrin react with amino acids, producing a colored solution. This protocol is used to detect the presence of amino acids in certain substances by using a solution of alcohol, ninhydrim and water. Technicians mix some drops of the analyzed substance to the ninhydrim solution, boiling it for 15 to 20 seconds. If the substance contains amino acids, it becomes blue-violet. However, if it contains an amino acid called proline, it turns yellow, according to the Central Connecticut State University.

Fingerprint Revelation

• This protocol uses a solution of ninhydrin and alcohol to reveal fingerprints. According to the International Association for Identification, technicians should first immerse the examined item in the solution for five seconds. Alternatively, they can spray the item. Later, they heat up to 176 degrees Fahrenheit at 60 percent to 70 percent relative humidity. If on the item, fingerprints become visible and are later examined under special lights.

Ninhydrin Test for Peptide Synthesis

• According to Peptide Station website, this protocol is used to detect ammonia in certain substances and to monitor peptide synthesis, which is related to a laboratory synthesis of proteins. Technicians use a solution of phenol or ethanol, the organic compound pyridine, ninhydrin and the analyzed substance, previously prepared as a resin. The mixture is heated for up to 5 minutes at 203 degrees Fahrenheit. A bluish color indicates an unfinished peptide synthesis, while pink indicates a completed reaction.