luminol(luminol), also known asLuminol, English name is 5-Amino-2,3-dihydro-1,4-phthalazinedione.It is yellow at room temperaturecrystalperhapsBeigePowder is a relatively stable chemical reagent.Its chemical formula is C8H7N3O2.At the same time, Luminol is also a strong acidrespiratory tractThere are certainIrritant effect。forensic medicineThe Luminol reaction, also known as the aminobenzoyl hydrazine reaction, can identify the blood stains that have been scrubbed for a long time.Biology uses LuminolDetect cellsCopper, iron andcyanideThe exists of.
Lumino was synthesized in 1853.In 1928, chemists discovered for the first time that this compound has a wonderful property that can emit blue light when it is oxidized.A few years later, someone thought of using this property to detect blood stains.The blood containshemoglobinThe oxygen we breathe in from the air depends on thisproteinDelivered to all parts of the body.Hemoglobin contains iron, which catalyzeshydrogen peroxideThe decomposition of hydrogen peroxide turns hydrogen peroxide into water and monooxygen, which oxidizes luminol to make it glow.When examining blood stains,hemoglobin(hemoglobin, a protein in hemoglobin responsible for transporting oxygen) catalyzes the reaction of luminol with hydrogen peroxide, showing thatTurquoiseFluorescence.This detection method is extremely sensitive. It can detect only one millionth of the blood content. Even if a small drop of blood drops into a large vat of water, it can be detected. This shows how difficult it is for criminals to clean the scene.
Luminol glows only after being treated with oxidant.Usually usedhydrogen peroxide solutionAnd onehydroxideMixed aqueous solution of alkali is used as activator.Under the catalysis of iron compounds, hydrogen peroxide is decomposed into oxygen and water:
Luminol and hydroxideReaction timeA double negative ion (Dianion) is generated, which can behydrogen peroxideThe decomposed oxygen is oxidized, and the product is aOrganic peroxide。ThisperoxideVery unstable, immediately decomposes into oxygen and generatesexcited state3-aminophthalic acid.Excited state toground stateDuring conversion, the released energy exists in the form of photons, and the wavelength is located in the blue part of visible light.1 Drop of blood can also be detected when mixed in 999 drops of water.But it hasOxidizabilityHowever, the color displayed and the duration of color development are different.
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Even if the bloodstains at the crime scene have been wiped or cleared, investigators can still use Lumino to find their location.In fact, the investigators sprayed Luminol and activator solution in the area to be investigated, and the iron in the blood immediately catalyzed Luminol's luminous reaction, making it produce blue light.The amount of catalyst required for this reaction is very small, so Luminol can be detectedtraceOf blood.The light lasts for about 30 secondsLong exposureThe photos ofsurrounding environmentIt can't be too bright.
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1. Luminol in coppercopper alloyOr somebleaching agentsIt will emit fluorescence in the presence of, which will strongly cover up the existence of blood stains.
2. Luminol can detect a small amount of blood in animal blood and urine, so if the test room contains urine or animal blood, the test results will be biased.
3. Lumino andExcretaThe light emitted by reaction is the same as that emitted by reaction with blood.
4. Luminol may interfere with other tests, but Luminol does not interfereDNAExtraction of.
The following methods are usually adopted to avoid interference in inspection:
1. Let the site dry for a few days,bleaching agentsOfInterference effectWill disappear, and even if the bloodstain passes many years, it can make Lumino shine.
2. Use some kind of energy to restrainHypochloric acidInterfering compounds.Obviously, it can't be usedantioxidant, because that would also inhibit the reaction between the blood stain and Lumino.People'sChemical structureFor example, suitable inhibitors have been found for the chlorine atoms it contains.The safest way is to use other methods to confirm that it is indeed a blood stain after the substance suspected of blood stain is detected by Lumino luminescence method.
Moreover, it was found that after the blood stain was treated by Lumino, it containedgenetic materialDNA has not been destroyed and can be extracted for identification.
Criminal Investigation Middle School
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stayCriminal InvestigationInluminolThe reaction, in general, is that as long as there is blood spattering and stained on any object at the murder scene, no matter how it is cleared afterwards, as long as Luminol reagent is sprayed on it and observed in the dark environment, there will be blue white fluorescence due to fluorescence reaction where there was blood stain.hydrochloric acidYes, just because there are blood molecules, it is OK to react them, but it will leave traces of reaction.
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In May 2024, a middle school in Qiqihar, Heilongjiang Province perfectly reproduced "blue tears" through chemical experiments - two students of the school poured two kinds of solutions into a flask connected with a funnel and a long tube, and the solution produced a chemical reaction and emitted blue fluorescence.[1]
Experiment principle: Four reagents, hydrogen peroxide, potassium ferrate, sodium hydroxide and luminol, were used in the chemical experiment. Hydrogen peroxide and potassium ferrate were mixed into one beaker, and sodium hydroxide and luminol were mixed into another beaker. Then a boy and a girl held beakers with different solutions respectively and slowly injected the solutions into the funnel,The amazing "blue tears" effect appeared on the scene.[1]
