2: Chemiluminescence Reagents
- Page ID
- 76108
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- 2.1: Luminol
- Luminol is the common name for 5-amino-2,3-dihydro-1,4-phthalazinedione (often called 3-aminopthalhydrazide). Oxidation of luminol produces excited 3-aminophthalate, which on relaxation emits light (λmax = 425 nm) with quantum yield of 1%. Alternatively, luminol chemiluminescence may be triggered electrochemically.
- 2.2: Lophine and pyrogallol
- Lophine and pyrogallol are the earliest-known chemiluminescence reagents. Lophine exhibits lemon yellow chemiluminescence in solution and is one of the few long-lasting chemiluminescent molecules. It forms dimers that have piezochromic and photochromic properties. It has been proposed as an analytical reagent for trace metal ion detection.
- 2.3: Luciferins
- Luciferases are enzymes that catalyse light-emitting reactions in living organisms - bioluminescence. They occur in several species of firefly and in many species of bacterium. Firefly Luciferases are extracted by differential centrifugation and purified by gel filtration. Luciferins are substrates of luciferases . Firefly luciferin emits at 562 nm on reaction with oxygen, catalysed by luciferase in the presence of adenosine triphosphate (ATP) and magnesium ions.
- 2.4: Lucigenin and coelenterazine
- Lucigenin is used in a wide variety of assays, especially those involving enzymatic production of hydrogen peroxide, and as a label in immunoassays. It reacts with various reductants, including those present in normal human blood[2], such as glutathione, uric acid, glucuronic acid, creatinine, ascorbic acid and creatine. The chemiluminescence intensity for a mixture of these analytes is equal to the sum of the intensities, measured separately for each analyte present.
- 2.5: Dioxetanes and oxalates
- Peroxy-oxalate chemiluminescence (PO-CL) was first reported in 1963 as a very weak bluish-white emission from oxalyl chloride, Cl-CO.CO-Cl, on oxidation by hydrogen peroxide; a similar blue emission occurs from related oxalyl peroxides. Much more intense emission is obtained in the reaction between aryl oxalates and hydrogen peroxide in the presence of a fluorophore; it is this version of the reaction that is analytically useful.
- 2.7: Manganese
- Manganese (VII) in the form of potassium permanganate has been used as a chemiluminescence reagent for several decades. A broad band of red light is emitted on reaction with over 270 compounds in acidic solution. Among the organic analytes are morphine and a wide range of other pharmaceuticals, phenolic substances, amines and hydrazines in addition to well-known reductants such as ascorbic acid and uric acid
- 2.8: Cerium
- Cerium(IV)-based chemiluminescence systems involve the reduction of cerium(IV), which suggests that the emitter is a cerium(III) species. The chemiluminescence reaction is carried out in an acidic medium (generally sulfuric acid) and has been applied for the determination of substances of biological interest.
- 2.9: Ruthenium
- The chemiluminescence involving tris(2,2'-bipyridyl)ruthenium(II), [Ru(bpy)3]2+, is most interesting. It involves the oxidation of [Ru(bpy)3]2+ to [Ru(bpy)3]3+, which is followed by reduction with an analyte species to produce an emission of light.
Thumbnail: Chemiluminescence after a reaction of hydrogen peroxide and luminol. This is an image from video youtu.be/8_82cNtZSQE. (CC BY-SA 4.0; Tavo Romann).