14 DAY TRIAL // Luminol is mostly known to us as a chemiluminescent compound used by law enforcements in crime scene investigations to detect traces of blood, even after the crime scene has been thoroughly cleaned in order to conceal the violent events that took place in a particular location. What is not usually told in various shows featuring the use of luminol is that it can also turn luminescent while reacting with certain organic compounds containing various levels of copper, iron or cyanides, and in some cases with urine, feces and other substances containing copper alloys.
Luminol is basically 5-Amino-3,2-dihydro-1,4 phthalazinedione, a chemical compound that can be obtained from 3-nitrophthalic acid. It appears as a white-yellowish solid, soluble in water, which glows a blue light when combined with certain oxidizing agents. The light signals that the reaction is taking place and there's some energy release involved.
Before use however, luminol must be first activated with the proper oxidant, usually a mix of hydrogen peroxide and a hydroxide salt. The obtained solution is then reacted with a catalyst, the iron contained in blood in the case of crime forensics, resulting in a compound known as dianion.
Forensics
As we said earlier, luminol can be successfully used to detect trace amounts of blood. Usually, investigators spray luminol only in a certain area of investigation because, given the amount of catalyst required in relation to the quantity of luminol, even incredibly small traces of blood can determine the compound to turn luminescent. The light released during the reaction can be observed fairly easy in a dark environment and may take up to 30 seconds before it becomes too faint to be observable to the naked eye or to be documented.
An alternative substance that may be used to obtain a similar effect is fluorescein, yet another chemiluminescent compound that works much in the same way as luminol does, although it requires a rather different preparation procedure.
Disadvantages
The reaction between luminol and the activator solution can also be catalyzed by certain bleaches, meaning that if the crime scene has been cleaned with a bleach solution, the use of luminol to detect blood will immediately result in a glowing pattern corresponding to the cleaned area. Urine may routinely contain traces of blood as well, thus a luminol test of a urine contaminated area could lead to inaccurate results.
Also, luminol might make it impossible for the analysts to perform certain forensic tests, albeit in the case of DNA extraction, it actually gives investigators a helping hand.