Chemiluminescent signal

In this work the development of mathematical model is done assuming simplifications of physico-chemical model of peroxide oxidation of the model system with the chemiluminesce intensity as the analytical signal. The mathematical model allows to describe basic stages of chemiluminescence process in vitro, namely spontaneous luminescence, slow and fast flashes due to initiating by chemical substances e.g. Fe +ions, chemiluminescent reaction at different stages of chain reactions evolution. 

An instrument for measuring nitrogen oxides based on chemiluminescence is shown in Fig. 13.49. The ozone required for the reaction is produced in the ozone generator, which is part of rhe device. One of the reaction chamber walls is an optical filter through which a red-sensitive photomultiplier tube measures the chemiluminescence radiation intensity and converts it into a current signal. 

The potential for improved chemiluminescent detection is large, since the efficiency for activation of the acceptor is less than 0.01%. A thousand-fold increase in signal could be anticipated from this reaction. 

The authors also demonstrated a low-technology method for recording the chemiluminescent signal of the bDNA assay. The light emission was recorded on black-and-white film Polaroid film using a handheld camera. The bDNA assay could be applicable to field situations because of the stability of the reagents and the ability to record the data without the use of sophisticated equipment. 

The intensity of chemiluminescence signal from a heated polymer and the kinetics of its change with time or temperature is determined by [30] ... 

A direct oxidation of polymer additive, which may occasionally give a much stronger signal than the oxidation of polymer itself. This is very important as it may lead to an erroneous relation between the rate of polymer oxidation and chemiluminescence intensity. 

Figure 9 demonstrates the fact that the chemiluminescence process occurs predominantly in the amorphous phase of the polymer. Low molar mass dicaproyl hexamethylene diamide is a fully crystalline compound the chemiluminescence signal under isothermal conditions below the melting point (136°C) at 130°C is very low, but it becomes rather strong after the crystallites of... 

In some laboratories chemiluminescence intensity and DSC signals from samples situated in one oven were obtained in parallel. Blakey and George [42], for example, presented the correlation between DSC signal and chemiluminescence (CL) intensity I during oxidation of PP. The quadratic dependence of I on DSC may be well seen in Figure 11. 

Figure 22 Continual changes of the intensity of chemiluminescence signal with concentration of oxygen in the surrounding atmosphere, 180°C, for Whatman cellulose paper. Numbers are % vol. of oxygen in the mixture with nitrogen.

Based on IgG-bearing beads, a chemiluminescent immuno-biochip has been also realized for the model detection of human IgG. Biotin-labeled antihuman IgG were used in a competitive assay, in conjunction with peroxidase labelled streptavidin59. In that case, the planar glassy carbon electrode served only as a support for the sensing layer since the light signal came from the biocatalytic activity of horseradish peroxidase. Free antigen could then be detected with a detection limit of 25 pg (108 molecules) and up to 15 ng. 

The second label also may be a fluorescent compound, but doesn t necessarily have to be. As long as the second label can absorb the emission of the first label and modulate its signal, binding events can be observed. Thus, the two labeled DNA probes interact with each other to produce fluorescence modulation only after both have bound target DNA and are in enough proximity to initiate energy transfer. Common labels utilized in such assay techniques include the chemiluminescent probe, N-(4-aminobutyl)-N-ethylisoluminol, and reactive fluorescent derivatives of fluorescein, rhodamine, and the cyanine dyes (Chapter 9). For a review of these techniques, see Morrison (1992). 

The chemiluminescence technique has been used to determine trivalent chromium in seawater. Chang et al. [187] showed Luminol techniques for determination of chromium (III) were hampered by a salt interference, mainly due to magnesium ions. Elimination of this interference is achieved by seawater dilution and utilising bromide ion chemiluminescence signal enhancement (Fig. 5.7). The chemiluminescence results were comparable with those obtained by a graphite furnace flameless atomic absorption analysis for the total chromium present in samples. The detection limit is 3.3 x 10 9 mol/1 (0.2 ppb) for seawater with a salinity of 35%, with 0.5 M bromide enhancement. 

Finally, Yamada and Suzuki made a comparative study of the use of DDAB, HTAB, STAC, and CEDAB to improve the sensitivity and selectivity of the determination of ultratraces of Cu(II) by means of the CL reaction of 1,10-phenanthroline with hydrogen peroxide and sodium hydroxide, used as detection in a flow injection system [46]. Of the four cited surfactants it was found that CEDAB causes the greatest enhancement of the chemiluminescent signal (Fig. 12) (an enhancement factor of 140 with respect to the absence of surfactant). 

The target for optimization in FTA with CL detection is to adjust all experimental factors in such a way so that the detector views as much radiation as possible while the chemiluminescent solution flows through the cell. Hence the kinetics of the flow and detector system should be monitored to match the kinetics of the reaction and generate maximum intensity inside the cell. The effect of experimental variables on the CL signal cannot be exactly predicted in advance and there is not enough theoretical background to support any suggestion. 

The most widely used gas-phase chemiluminescence reagent is ozone. Analytically useful chemiluminescence signals are obtained in the reactions of ozone with NO, SO, and olefins such as ethylene and isoprene, but many other compounds also chemiluminesce with ozone. Ozone is conveniently generated online at mixing ratios of =1-5% by electrical discharge of air or 02 at atmospheric pressure [14]. 

While investigating the potential for an instrument to measure atmospheric dimethyl sulfide (DMS) [69], discussed below, Hills et al. investigated the possibility of adding H2 to the reaction cell to provide chemical amplification of the chemiluminescence signal via the catalytic chain reaction ... 

Selectivity derives from the fact that the analyte of interest generates its signal in the presence of compounds that normally interfere in fluorescence measurement and that do not themselves produce light when the chemiluminescent reagents are mixed together. 

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