Blood in the secret

I like to watch United States Discovery Channel's "new detective" program. In the program sometimes such lens: it was reported to the police of his family had disappeared, the police came to investigate, at home in search of missing persons, did not find that strange. On the ground, wall spray reagents, close the blinds, only to discover that the ground, wall there is something in the lumps, indicating that it was blue blood.

The original is missing persons were killed in the home, before he died of a massive bleeding, but cleaning up the room murderer. Have you ever thought what police agents, why can turn invisible blood detected?

Police sprayed the main constituents of reagents is hydrogen peroxide and luminol. Luminol is a kind of synthetic organic compounds, as early as 1853 by synthesis. To 1928, chemists discovered this compound has a wonderful feature that can be issued by the oxidation of Blu-ray. A few years later, people want to use this feature to detect blood. Blood contains hemoglobin, we from the oxygen in the air is inhaled by the protein transport to all body parts. Hemoglobin contains iron and iron to catalytic decomposition of hydrogen peroxide into water, hydrogen peroxide and single oxygen oxygen, single re-oxidation of luminol let it glow. This extremely sensitive detection methods, can detect the millionth content of blood, even a small drop of blood drops to one big cylinders in water can also be detected, it can be seen just how criminals are difficult to clean the site.

See luminol chemiluminescence, will know this detection method is actually not so reliable, not a Jet found luminol reagent on the ground a Blu-ray hurray "blood". Since luminol chemiluminescence is oxidation, which means that there are a lot of oxides and can act as a catalyst of metal can let luminol chemiluminescence, this includes the daily use of sodium hypochlorite bleaching agent. If criminals bleach washing over the scene, it is possible to interfere with the use of luminol. These two luminescent situation is slightly different, bleach is caused by light flashes quickly, and blood stains caused by luminous is gradually emerging. Experienced detective is usually able to distinguish between the two, but it is not always possible.

What can be done several ways, one is for on-site dry for a few days, the effect of interfering with bleaching agents will disappear, and the blood even after many years, also allow luminol chemiluminescence. Another way is to use some interference of hypochlorite inhibition of compounds. Obviously you cannot use antioxidants, because that will bring the blood and the reaction of luminol also stifle. People for the chemical structure of hypochlorite, for example, for it contains chlorine atoms, find a suitable inhibitor. The surest way is using luminol chemiluminescence assay to a substance suspected of blood stains, use another method to determine that it is blood. It has been found that the blood was luminol processed, it contains the genetic material DNA has not been compromised, you can extract out do identification. This virtually foolproof.

Similar principles were applied in clinical testing. Physical examination of a routine examination called for questioning "is occult blood," this refers to the amount of rarely gastrointestinal hemorrhage, inclusion in the red blood cells in the stools and digestion decomposition, not with the naked eye and a microscope found bleeding. Now available for testing chemical reagents. Doctors use filter paper soaked in some patients with fecal matter, and then drops containing tetramethyl benzidine and peroxide of strontium reagents. Permanganate will produce hydrogen peroxide. If the stool in hemoglobin, hemoglobin determination of iron in the decomposition of hydrogen peroxide will be put into a single oxygen, colorless tetramethyl benzidine and single oxygen reaction turns to blue.