Luminol, also known as luminol, is a kind of yellow crystal or beige powder at room temperature, which is a relatively stable chemical reagent. At the same time, luminol is a kind of strong acid, which can stimulate eyes, skin and respiratory tract.
It is one of the oldest and most commonly used reagents. It can be oxidized by peroxide under alkaline conditions and emit light at the same time.
The redox reaction between luminol and peroxide needs catalyst, which is usually multivalent metal ions, peroxidase such as iron, horseradish peroxidase, etc. this method is often used to detect the content of peroxide, heavy metal, peroxidase, as well as the derived free radical detection, toxicological analysis and based on peroxidase and glucose oxidase The method of analysis is introduced.
In general, the chemiluminescence reaction between luminol and hydrogen peroxide is very rapid in the presence of some catalysts. The most commonly used catalysts are metal ions. In a large concentration range, the concentration of metal ions is directly proportional to the luminous intensity, so the chemiluminescence analysis of some metal ions can be carried out. Using this reaction, the organic compounds containing metal ions can be analyzed, achieving high sensitivity. The second is to use the inhibition of organic compounds on luminol chemiluminescence reaction to determine the organic compounds with quenching effect on chemiluminescence reaction. Third, indirect determination of inorganic or organic compounds by coupling reaction.
Luminol luminescent principle
First, sodium hypochlorite oxidizes luminol to make it luminescent;
Second, hydrogen peroxide reacts with sodium hypochlorite to form oxygen to oxidize luminol and make it luminescent
The first is the reaction equation of sodium hypochlorite and hydrogen peroxide: NaClO + H2O2 = = NaCl + O2 + H2O
Secondly, luminol reacts with hydroxide to form a dianion, which can be oxidized by oxygen decomposed by hydrogen peroxide to form an organic peroxide. The peroxide is very unstable and immediately decomposes into nitrogen (after luminol is oxidized by organic oxidants such as dimethyl sulfoxide, it does not generate nitrogen, but nitrogen-containing organic compounds), and forms excited 3-aminophthalic acid. During the transition from excited state to ground state, the released energy exists in the form of photons, and the wavelength is located in the blue part of visible light.
Luminol (luminol ammonia) as a chemiluminescence reagent is often used in the detection, however, some people will ask, luminol in the application of the general will choose which luminescent detection method? The three methods that Desheng told you were accelerating the luminescence of catalyst, indirect determination of inhibitor and indirect determination by coupling.
It is estimated that the luminescent speed of luminol detection is too slow, so some catalysts are often added to accelerate the detection. In chemiluminescence immunoassay, peroxides, especially horseradish peroxidase, are often used as catalysts. In addition to horseradish peroxidase, catalysts also include some metal complexes, transition metal ions, such as hemoglobin, iron ions, manganese ions, etc.
If there is acceleration, there will be inhibition. Some organic compounds will inhibit luminol luminescence by inhibitors, such as reducing compounds containing phenolic hydroxyl groups. This can be used for indirect determination of such organic compounds. This is the second method.
Indirect determination by coupling is to combine one reaction that can produce or consume chemiluminescence reactants with another chemiluminescence reaction, so as to realize Indirect Chemiluminescence Determination of some substances. This method is used to determine the purity of some substrate enzymes.
