Luminol
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Image:Luminol synthesis.gif Image:Luminol chemiluminescence molecular representation.gif
Luminol is a chemical used by forensic investigators to detect blood.
- formula:<math>C_8H_7N_3O_2</math>
- CAS number: 521-31-3
Synonyms
- 5-Amino-2,3-dihydro-1,4-phthalazinedione [521-31-3]
- o-aminophthaloyl hydrazide
- o-aminophthalyl hydrazide
- 3-Aminophthalhydrazide
- 3-aminophthalic hydrazide
Use by Crime Scene Investigators
Theory
Luminol is used by crime scene investigators to locate occult blood, even if it has been cleaned or removed. Using its natural property of chemiluminescence, it luminesces upon reacting with hydrogen peroxide. Iron in hemoglobin, a pigment present in blood, is provided as a catalyst in the luminescence. The glow lasts for about 30 seconds and is blue. Detecting the glow requires a fairly dark room. Any glow detected is documented by a long exposure photograph.
Drawbacks
Nevertheless, Luminol has drawbacks that can keep it from detecting just blood that has been shed in a crime:
- Luminol also fluoresces in the presence of copper or an alloy of copper, certain bleaches and horseradish.
- Luminol will also detect the small amounts of blood present in urine and it can be distorted if animal blood was present in the room that is being tested.
- Luminol presence may prevent other tests to be performed on a piece of evidence. However, it has been shown that DNA can be successfully extracted from samples treated with luminol reagent.
- Luminol is listed as possible carcinogen but has not yet been proven as such.
Other uses
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- Medical: Used to conduct biochemical assays
- Amusement: Glowing light sticks
- Education: Getting young people interested in science
Details on using luminol to show light:
Add 5 mL of luminol solution to 15 mL of luminol activator solution. The ratio of luminol solution to luminol activator determines the intensity and the duration of the blue light produced. The 1:3 ratio suggested here produces a relatively bright light of short duration. Using more luminol solution and less luminol activator produces a dimmer blue light of longer duration. These solutions are available at a local science supplier.