Can luminol repeatedly detect blood luminescence?
Release time:
2020-10-03
Luminol is a chemical fluorescent molecule that can be converted into excited amino phthalic acid in the presence of hydrogen peroxide, which emits strong fluorescence. It is a strong acid and has a certain irritating effect on eyes, skin and respiratory tract. Luminol is widely used in criminal investigations. Even if the blood stains at the crime scene have been wiped or removed, forensic doctors can still use luminol to find their location. But the light-emitting time lasts about 30s, the surrounding environment can not be too bright, we should take pictures and observe as much as possible. If the reaction speed is too fast and the luminous efficiency is not recorded and the luminous efficiency disappears, can we still use luminol for a second spray to test the blood? First of all, we need to know what makes Luminol shine.
Luminol's luminescence principle:
One is that sodium hypochlorite oxidizes luminol to make it glow;
The second is that hydrogen peroxide reacts with sodium hypochlorite to generate oxygen and oxidize luminol to make it glow:
The first is the equation for the reaction of sodium hypochlorite and hydrogen peroxide: NaClO + H2O2 = = NaCl + O2 + H2O
Secondly, when luminol reacts with hydroxide, a double negative ion (Dianion) is formed, which can be oxidized by oxygen generated by the decomposition of hydrogen peroxide, and the product is an organic peroxide. The peroxide is very unstable and immediately decomposes nitrogen (Luminol is not oxidized by organic oxidants such as dimethyl sulfoxide to generate nitrogen, but to generate nitrogen-containing organics), and generates excited 3-aminophthalic acid . In the transition from the excited state to the ground state, the released energy exists in the form of photons with a wavelength in the blue part of visible light.
Earlier we talked about the luminescence principle of luminol, and learned that the luminescence time of luminol is only 30s, and the process reaction is quickly over. If you accidentally fail to react, you won't see this glowing process. Can we continue to use the luminol reaction after once? Luminol's principle of luminescence is that hemoglobin contains iron, and iron can catalyze the decomposition of hydrogen peroxide, turning hydrogen peroxide into water and monooxygen, and monooxygen oxidizing luminol to make it glow. When we use luminol, it will not change and oxidize the iron ions in the blood, and iron ions can continue to play a catalytic role as a catalyst. Therefore, the light-emitting process can continue to react. So the second use of luminol can still see the light.
Luminol has a wide range of uses. In addition to criminal investigation, it can also be used for immunochemiluminescence reaction, for the detection of sex hormones, drug abuse, and cardiovascular and reproductive diseases. Luminol developed and produced by Desheng has a purity of over 98%, good water solubility, stable process, and small batch-to-batch variation.
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