Luminol
Luminol is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but insoluble in water.
Forensic science
Forensic science is the application of science to criminal and civil laws. Forensic scientists collect, preserve, and analyse scientific evidence during the course of an investigation. While some forensic scientists travel to the scene to collect the evidence themselves, others occupy a purely laboratory role, performing analysis on objects brought to them by other individuals.
Hemoglobin
Hemoglobin; also spelled haemoglobin and abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates (with the exception of the fish family Channichthyidae) as well as the tissues of some invertebrates. Hemoglobin in the blood …
Can luminol detect small amounts of blood?
Luminol will also detect the small amounts of blood present in urine, and it can be distorted if animal blood is present in the room that is being tested. * Luminol reacts with fecal matter, causing the same glow as if it were blood. How does luminol detect blood?
What is the reaction between blood and luminol?
Luminol (Blood) The light, or luminescence, emitted in the luminol reaction is thought to result when an oxidizing agent, such as blood, catalyzes the oxidation of luminol by hydrogen peroxide in a basic solution. The reaction is not specific to blood, however, as other oxidizing agents such as sodium hypoclorite (bleach), certain metals,...
How long does it take for blood to glow with luminol?
The iron in blood catalyses the luminescence. The amount of catalyst necessary to cause the reaction is very small relative to the amount of luminol, allowing detection of even trace amounts of blood. The blue glow lasts for about 30 seconds per application.
What does luminol look like?
When luminol is sprayed evenly across an area, trace amounts of an activating oxidant make the luminol emit a blue glow that can be seen in a darkened room. The glow only lasts about 30 seconds, but can be documented photographically.
What else can luminol detect?
Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, cyanides, as well as specific proteins via western blotting.
Is luminol a blood test?
Forensic scientists spray luminol onto surfaces at crime scenes to detect invisible blood stains. Wherever the luminol touches blood, it glows, and the glow is bright enough to be photographed.
How many years can luminol detect blood?
The authors have previously reported on the use of the Luminol reagent to detect blood in soil up to fours years following deposition [1-3]. Since 1937 the Luminol reagent has been used to detect latent bloodstains [4].
Does bleach show up with luminol?
There are two types of bleach found in household cleaning products. Chlorine-based bleaches are known to make bloodstains invisible, but applying chemicals such as luminol or phenolphthalein will still reveal the presence of haemoglobin – crucial for identifying blood – even after up to 10 washes.
What can cause a false positive luminol test?
It is hypothesized that luminol will show a false positive reaction on substances, metals, and surfaces containing iron. Also, that surfaces sprayed with blood then cleaned or concealed will still test positive with luminol chemeluminscene.
What does a positive luminol test look like?
The working solution may then be sprayed onto surfaces to test for the presence of blood. A positive result for luminol can be seen as the emission of blue light, a process referred to as chemiluminescence.
Does luminol glow in the dark?
Luminol is an organic compound which, when oxidized, emits light — a phenomenon known as chemiluminescence. This is similar to the reactions that fireflies uses to emit light, and to those used in "glow-sticks" and some roadside emergency lights.
Is luminol used in glow sticks?
Glow Stick Chemical Reaction There are several chemiluminescent chemical reactions that may be used to produce light in glow sticks, but the luminol and oxalate reactions are commonly used.
Does luminol destroy DNA?
Luminol has been widely used in the field of crime scene investigations to detect latent blood; however, luminol has the tendency to destroy DNA evidence.
Can hydrogen peroxide hide blood from luminol?
It can affect the luminol and Bluestar® Forensic tests by causing a negative result, even in the presence of blood. Hydrogen peroxide is a common disinfectant and a necessary component of most presumptive blood tests, however, bulk quantities of it in the luminol reaction stop the reaction from proceeding.
Can luminol be fooled?
Moreover, they've also established that their new technique isn't fooled by common materials that can cause false positives with luminol, which include bleach, rust and coffee stains.
What gets rid of all traces of blood?
Scientists have shown that traces of blood in various materials are eliminated completely when they are washed with detergents containing active oxygen.
Why do investigators use luminol?
Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, cyanides, as well as specific proteins via western blotting.
How does luminol work in crime scene?
Crime scene investigators use luminol to find traces of blood , even if someone has cleaned or removed it. The investigator sprays a solution of luminol and the oxidant. The iron in blood catalyses the luminescence. The amount of catalyst necessary to cause the reaction is very small relative to the amount of luminol, allowing detection of even trace amounts of blood. The blue glow lasts for about 30 seconds per application. Detecting the glow requires a fairly dark room. Any glow detected may be documented by a long-exposure photograph .
What is the name of the substance that enhanced the luminescence of luminol in an alkaline solution
History. In 1928, German chemist H. O. Albrecht found that blood, among other substances, enhanced the luminescence of luminol in an alkaline solution of hydrogen per oxide. In 1936, Karl Gleu and Karl Pfannstiel confirmed this enhancement in the presence of haematin, a component of blood.
How is luminol made?
Luminol is synthesized in a two-step process, beginning with 3-nitro phthalic acid. First, hydrazine (N 2 H 4) is heated with the 3-nitrophthalic acid in a high-boiling solvent such as triethylene glycol and glycerol. An acyl substitution condensation reaction occurs, with loss of water, forming 3-nitrophthalhydrazide.
What is the activator for luminescence?
Chemiluminescence of luminol. To exhibit its luminescence, the luminol must be activated with an oxidant. Usually, a solution containing hydrogen peroxide (H 2 O 2) and hydroxide ions in water is the activator.
When was luminol first synthesized?
The compound was first synthesized in Germany in 1902, but was not named "luminol" until 1934.
Who discovered the luminol test?
In 1939, San Francisco pathologists Frederick Proescher and A. M. Moody made three important observations about luminol: although the test is presumptive, large areas of suspected material can be examined rapidly; dried and decomposed blood gave a stronger and more lasting reaction than fresh blood; and.
What is the chemical that causes luminol to oxidize?
It can be oxidised by the chemicals in bleach, such as sodium chlorate; low levels of blood in urine can also trigger the reaction. Additionally, enzymes can also lend a hand.
Can luminol be oxidized?
Wrong! Unfortunately, there are several other substances that are capable of catalysing the oxidation of luminol. It can be oxidised by the chemicals in bleach, such as sodium chlorate; low levels of blood in urine can also trigger the reaction. Additionally, enzymes can also lend a hand.
What happens to the latent blood traces after using luminol?
A simulation of luminol at work: Before spraying luminol, there's no sign of blood. After spraying luminol, the latent blood traces emit a blue glow. Much of crime scene investigation, also called criminalistics, is based on the notion that nothing vanishes without a trace.
How long does blood cling to surfaces?
Tiny particles of blood will cling to most surfaces for years and years, without anyone ever knowing they're there. The basic idea of luminol is to reveal these traces with a light-producing chemical reaction between several chemicals and hemoglobin, an oxygen-carrying protein in the blood.
How is luminol used in serology?
Luminol is routinely used in forensic serology to locate and identify blood traces and stains which are not visible to the naked eye and it is very sensitive. Luminol produces a bluish-white light when peroxidase is added to it in the presence of blood and it is the heme portion of hemoglobin that reacts with the peroxidase. The color and intensity of the light can be measured. Samples of bone from 80 nonpathological femurs were subjected to luminol testing. The samples, from 40 males and 40 females, were grouped into five time periods according to the known time of death, but with sufficient intervals to prevent overlaps in the positive results from the tests. The time periods were 1 month to 3 years, 10–15 years, 25–35 years, 50–60 years, and greater than 80 years. A camera recorded the chemiluminescence and brightness was measured by a computer software program (Olivetti PC PRO 486/33 MHz- 8MbRAM). The test was always positive and intense in bones from the first group; 80% of the second group showed luminescence visible to the eye but luminescence gradually reduced in positivity and brightness as the PMI increased. After a PMI of 25 years it was negative in 70% and after 50 years only 10% were positive. Introna and colleagues suggested that the luminol test could be useful in determining the TSD from skeletal remains, especially when only isolated or fragmented bones were recovered, but it should be tested on a wider sample of bones with a closer PMI range in order to establish its statistical significance.
What is luminol used for?
Luminol is frequently used as a searching or enhancement method at the crime scene. The test is based on the ability of the luminol molecule to be oxidized by the reaction of sodium perborate with an oxidizing agent such as hemoglobin (or other strong oxidizers such as iron, bleach, cleaning agents, and some foodstuffs).
What is the competition between biotin and a biotin luminol derivative for avidin?
The competition between biotin and a biotin luminol derivative for avidin was utilized for a chemolumimetric detection. Biotin is covalently linked to the amine function of isoluminol to yield the conjugate. This conjugate emits light when oxidized by either a hydrogenperoxidase–lactoperoxidase or a superoxide. The peak light intensity increases about 10-fold when the conjugate is incubated with avidin prior to oxidation. When the isoluminol-biotin conjugate and free biotin compete for the avidin binding sites, the peak light intensity produced in subsequent chemiluminescent reactions decreases with increasing biotin levels. In this way, biotin is measured quantitatively at levels as low as 50 nM.
What are the advantages and disadvantages of Leuco fluorescein?
Their advantage is that they create a brighter fluorescence than luminol, and the fluorescence lasts longer than the brief luminol fluorescence. Each, however, has a disadvantage. Leuco fluorescein requires an ALS to stimulate the fluorescence; the fluorescence does not come from a chemical reaction with the blood.
How much luminol to add to DMSO?
Luminol stock solution (100 mM): Add 177.09 mg of luminol to 10 mL of DMSO solution in a polystyrene tube and mix well. The tube must be wrapped with aluminum foil to avoid light exposure to luminol. Stock solution can be stored at room temperature until expiration date.
What is the ratio of luminol to sulfosalicylic acid?
However, experiments have shown that at a ratio of 3:1 , the luminol:sulfosalicylic acid combination reagent both fixes the blood and still fluoresces it nicely. Besides washing a bloodstained area with just soap and water, the use of bleach may also be used. To the criminal, this may represent a double benefit.
What light to use for leuco fluorescein?
Use a blue light with an orange filter to stimulate leuco fluorescein. BlueStar, though living up to its claims of a brighter fluorescence over a longer time period, is substantially more expensive than luminol. The advantage of having a brighter, longer-lasting fluorescence, nevertheless, is a great one.
What does a luminescent pattern on a surface indicate?
Besides being useful in locating minute amounts of blood, the luminescent pattern observed on surfaces could indicate such things as; the route of exit from the crime scene, drag marks in blood, or an attempt to clean up blood. Above left: a footwear impression in blood that has been enhanced with luminol reagent.
What is the term for the search for blood at a crime scene?
Luminol (Blood) The search for the presence of blood at a crime scene is normally done by close visual examination. The possibility exists, however, that blood may be present in amounts too little to see with the unaided eye, or that the blood at the scene had been “cleaned up” prior to arrival of the crime scene team.
What is the reaction of light emitted by blood?
The light, or luminescence, emitted in the luminol reaction is thought to result when an oxidizing agent, such as blood, catalyzes the oxidation of luminol by hydrogen peroxide in a basic solution.
Overview
Luminol (C8H7N3O2) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but insoluble in water.
Forensic investigators use luminol to detect trace amounts of blood at crime sc…
Synthesis
Luminol is synthesized in a two-step process, beginning with 3-nitrophthalic acid. First, hydrazine (N2H4) is heated with the 3-nitrophthalic acid in a high-boiling solvent such as triethylene glycol and glycerol. An acyl substitution condensation reaction occurs, with loss of water, forming 3-nitrophthalhydrazide. Reduction of the nitro group to an amino group with sodiu…
Chemiluminescence
To exhibit its luminescence, the luminol must be activated with an oxidant. Usually, a solution containing hydrogen peroxide (H2O2) and hydroxide ions in water is the activator. In the presence of a catalyst such as an iron or periodate compound, the hydrogen peroxide decomposes to form oxygen and water:
2 H2O2 → O2 + 2 H2O H2O2 + KIO4 → KIO3 + O2 + H2O
Use in criminal investigation
In 1928, German chemist H. O. Albrecht found that blood, among other substances, enhanced the luminescence of luminol in an alkaline solution of hydrogen peroxide. In 1936, Karl Gleu and Karl Pfannstiel confirmed this enhancement in the presence of haematin, a component of blood. In 1937, German forensic scientist Walter Specht made extensive studies of luminol's application to the detection of blood at crime scenes. In 1939, San Francisco pathologists Frederick Proesche…
Related molecules
• Luminol: 5-amino-2,3-dihydro-1,4-phthalazinedione ; 3-amino-phthalhydrazide ; 1,4-phthalazinedione, 5-amino-2,3-dihydro ; CAS: [521-31-3] C8H7N3O2 – MW: 177.16 λabs (in 0.1 N NaOH) λmax 1 : 347 nm & λmax 2 : 300 nm; EC (at λmax 1): 7650 L/mol × cm λabs / λem (MeOH): 355/413 nm
• Luminol, sodium salt: sodium 3-amino-phthalhydrazide; CAS: [20666-12-0] C8H6N3O2Na – MW: 199.12
See also
• Fluorescein
• Diphenyl oxalate
External links
• HowStuffWorks "How Luminol Works"
• Luminol demonstration in Turin