Principle of chemiluminescence

1964) can sometimes be detected, which occurs if the singlet oxygen is in high enough local concentration for reaction [3.7.4] to occur. Since this region is covered by most UV-visible spectrometers, it is still used quite extensively (Boveris et al., 1980 Cadenas and Sies, 1984). 

Sensitivity may be improved using single-photon counters as luminescence detectors. 

A liquid scintillation counter is actually two photon counters connected in coincidence for measuring the shower or pulse of electrons resulting from the relaxation of fluorescent molecules excited by b-particle emission. In the out-of-coincidence mode, the instrument is a single photon counter, i.e., it counts single photon events. 

The luminescence intensity measurements in relative counts/minute 

Systems undergoing lipid peroxidation accumulate malonyldialde-hyde (see Chapters 2 and 5), as has been observed in many biological systems. The amount of malonaldehyde accumulated correlates well with the chemiluminescence intensity observed, although the chemiluminescent species and the aldehydic lipid peroxidation product are formed by different pathways and at different times during the process of lipid peroxidation. 

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The NO analyzer is based on the principles of chemiluminescence to determine continuously the NO concentration in the sample gas stream. The analyzer should contain a NOg-to-NO converter, which converts the nitrogen dioxide (NO9) in the sample gas to nitrogen oxide (NO). An NOg-to-NO converter is not necessary if data are presented to demonstrate that the NO9 portion of the exhaust gas is less than 5 percent of the total NO9 concentration. 

The principle of chemiluminescence detection is a chemical reaction forming a species in the electronically excited state that emits a photon of measurable light on returning to their ground state. 

Fig. 4. Principle of chemiluminescent immunoassay (CLIA) of vitellogenin (Vg). Polyclonal antibodies raised against two distinct classes of Vg-derived yolk proteins (anti-/3 -component and anti-lipovitellin), which are derived from different parts of the same parent Vg molecule, can be utilized to develop a simultaneous one-step CLIA (right side of the figure). Alternatively, a single anti-Vg antibody can be used in a two-step CLIA (left side of the figure). Advantages of each type of CLIA are discussed in detail in section VI.2. IgG, immunoglobulin G.

In principle, one molecule of a chemiluminescent reactant can react to form one electronically excited molecule, which in turn can emit one photon of light. Thus one mole of reactant can generate Avogadro s number of photons defined as one einstein (ein). Light yields can therefore be defined in the same terms as chemical product yields, in units of einsteins of light emitted per mole of chemiluminescent reactant. This is the chemiluminescence quantum yield which can be as high as 1 ein/mol or 100%. 

PRINCIPLES OF FLOW INJECTION ANALYSIS WITH CHEMILUMINESCENCE DETECTION... 

The measuring principle of photosensitized chemiluminescence is applied in the Photochem. The principal functional units of the instrument are shown in Figure 3. 

Garcia-Campana AM, Baeyens WRG (2000) Principles and recent analytical applications of chemiluminescence. Analysis 28 686-698... 

It solely operates on the principle of photon emission. If P- or S-containing hydrocarbons are ignited in a hydrogen-rich flame, it gives rise to chemiluminescent species spontaneously which may subsequently be detected by a suitably photomultiplier device. Hence, FPD is regarded as a specific detector for P- or S-containing compounds. 

Several methods have been developed to estimate the exposure to such emissions. Most methods are based on either ambient air quality surveys or emission modeling. Exposure to other components of diesel emissions, such as PAHs, is also higher in occupational settings than it is in ambient environments. The principles of the techniques most often used in exhaust gas analysis include infrared (NDIR and FTIR), chemiluminescence, flame ionization detector (FID and fast FID), and paramagnetic methods. 

The analytic principles that have been applied to accumulate air quality data are colorimetry, amperometry, chemiluminescence, and ultraviolet absorption. Calorimetric and amperometric continuous analyzers that use wet chemical techniques (reagent solutions) have been in use as ambient-air monitors for many years. Chemiluminescent analyzers, which measure the amount of chemiluminescence produced when ozone reacts with a gas or solid, were developed to provide a specific and sensitive analysis for ozone and have also been field-tested. Ultraviolet-absorption analyzers are based on a physical detection principle, the absorption of ultraviolet radiation by a substance. They do not use chemical reagents, gases, or solids in their operation and have only recently been field-tested. Ultraviolet-absorption analyzers are ideal as transfer standards, but, as discussed earlier, they have limitations as air monitors, because aerosols, mercury vapor, and some hydrocarbons could, interfere with the accuracy of ozone measurements made in polluted air. 

Although, in principle, it is possible for some fraction of the events to follow the Odd surface beyond this second intersection and to thus lead to JOdd product molecules that might fluoresce, quenching is known to be rapid in most polyatomic molecules as a result, reactions which are chemiluminescent are rare. An appropriate introduction to the use of OCD s, CCD s, and SCD s as well as the radiationless processes that can occur in thermal and photochemical reactions is given in the text Energetic Principles of Chemical Reactions, J. Simons, Jones and Bartlett, Boston (1983). 

Figure 12.12—Chemiluminescence reactions using ozone. Schematic showing the principle of a nitrogen analyser based on the luminescence of nitrogen monoxide.

The oxides of nitrogen (NO and N02) can be determined with a method based on chemiluminescence, compound-specific light emission after excitation. The principle of this method is based on the following chemical reaction ... 

The principle of the experiment is to record the reaction signal (e.g., a chemiluminescence signal) as a function of the average number and to fit it by a Poisson distribution or by a linear combination of Poisson distributions. The order of the Poisson distribution which best fits the experimental data is a direct measure of the exact number of reactants involved in the chemical process under study, since the reactants are confined on a cluster of finite size. For instance, if the reaction signal is well fitted by the Poisson distribution P2 (jn)), when varying the average... 

Automated chemistry analyzers have traditionally relied on photometers and spectrophotometers for measurement of absorbance. Alternative approaches now being incorporated into analyzers include reflectance photometry and fluorom-etry. Immunoassay systems have used fluorescence (IMX), chemiluminescence (Centaur and Immulite), and electrochemiluminescence (ELECSYS) to enhance sensitivity. Ion-selective electrodes and other electrochemical teclmiques are also widely used. Principles of these measurement techniques have been discussed previously (see Chapter 4). This section reviews the special features and application of the various approaches to automated analysis. 

CLIA is similar to EIA and ELISA techniques except that the final receptor enzyme assay is replaced with a chemiluminescent tracer followed by measurement of light released as a result of the chemical reaction. The principles of a chemiluminescence competitive binding assay are shown in Figure 8-8. 

Fig. 7.3. Principle of acridinium-ester probe hybridization in solution and detection. Acridiniura-NHS is linked to allyl nucleotides (Section 7.3.1.2) in the probe. When the probe hybridizes with its target in solution, the acridinium moiety intercalates in the duplex. Unhybridized acridinium ester probes can be hydrolyzed selectively (Table 7.7, step 2), whereas protected acridinium ester remains intact (ID. After nonspecific chemiluminescence is sufficiently eliminated, specific chemiluminescence is measured (in). The whole procedure takes less than 30 min.

Figure 11.16 Reactions of chemiluminescence using ozone. The scheme above summarizes the principle of transformation of a sulfur compound oxidized to sulfur dioxide in the excited state by ozone. Below, the final reaction can be applied to the measurement of ozone just as readily as for ethylene.

Peroxyoxalate chemiluminescence detection has been shown to be a highly sensitive detection method " for the determination of A-nitrosamines and secondary amines in combination with reversed-phase HPLC. Fentomole limits of detection can be obtained with conventional instrumentation. The principle of the reaction is illustrated in Figure 12.3. 

The typical reaction of 1,2-dioxetanes is thermal decomposition. On warming tetramethyl-1,2-dioxetane in benzene or other solvents, blue light is emitted. Such a phenomenon is known as chemiluminescence [11]. It has been demonstrated that, according to the principle of conservation of orbital symmetry, one mole of acetone in an electronically excited state is formed. In this way, an electronically excited molecule (symbolized by ) is created by a thermal process. With emission of light, the ground state is restored ... 

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