Luminol (C8H7O3N3) is a versatile chemical that exhibits chemiluminescence, with a striking blue glow, when mixed with an appropriate oxidizing agent. It is a white to slightly yellow crystalline solid that is soluble in water and most polar organic solvents.
Luminol is used by forensic investigators to detect trace amounts of blood left at crime scenes as it reacts with iron found in haemoglobin. It is also used by biologists in cellular assays for the detection of copper, iron, and cyanides.
To exhibit its luminescence, the luminol must first be activated with an oxidant. Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide salt in water is used as the activator. In the presence of a catalyst such as an iron compound, the hydrogen peroxide is decomposed to form oxygen and water:
In a laboratory setting, the catalyst used is often potassium ferricyanide. In the forensic detection of blood, the catalyst is the iron present in hemoglobin. Enzymes in a variety of biological systems may also catalyze the decomposition of hydrogen peroxide.
When luminol reacts with the hydroxide salt, a dianion is formed. The oxygen produced from the hydrogen peroxide then reacts with the luminol dianion. The product of this reaction, an organic peroxide, is very unstable and immediately decomposes with the loss of nitrogen to produce 3-aminophthalic acid with electrons in an excited state. As the excited state relaxes to the ground state, the excess energy is liberated as a photon, visible as blue light.
Police: Ayla's blood was detected with luminol spray ; Some other substances react with the chemical, so a positive reaction requires a crime lab confirmation.
Jan 31, 2012; BEN McCANNA /Morning Sentinel Portland Press Herald (Maine) 01-31-2012 Police: Ayla's blood was detected with Luminol...
The effect of tea antioxidants on the light emissions of luminol and hydrogen peroxide solutions.(SOUTH CAROLINA JUNIOR ACADEMY OF SCIENCE ABSTRACTS)
Jan 01, 2005; The human body has naturally occurring ions which appropriate electrons from other atoms. These ions are most commonly referred...