Intensity, chemiluminescence light

Chemiluminescence measurement is based on the detection of the chemiluminescence light intensity (at constant temperature) versus time (Fig. 10.44). 

The chemiluminescence quantum efficiency of luminol is practically the same in anhydrous DMS0/base/02 and in the aqueous alkaline H202/hemin system [33]. Addition of small amounts of water to the DMSO system drastically diminishes, the chemiluminescence light intensity. In a mixed solvent of DMSO/28 mole water/potassium hydroxide/oxygen the relative intensity was only 1/30,000 of that in the DMSO/t-butoxide/02 system [43a]. 

Divalent copper, cobalt, nickel, and vanadyl ions promote chemiluminescence from the luminol—hydrogen peroxide reaction, which can be used to determine these metals to concentrations of 1—10 ppb (272,273). The light intensity is generally linear with metal concentration of 10 to 10 M range (272). Manganese(II) can also be determined when an amine is added to increase its reduction potential by stabili2ing Mn (ITT) (272). Since all of these ions are active, ion exchange must be used for deterrnination of a particular metal in mixtures (274). 

Luminol chemiluminescence has also been recommended for measuring bacteria populations (304,305). The luminol—hydrogen peroxide reaction is catalyzed by the iron porphyrins contained in bacteria, and the light intensity is proportional to the bacterial concentration. The method is rapid, especially compared to the two-day period required by the microbiological plate-count method, and it correlates weU with the latter when used to determine bacteria... 

Gorsuch and Hercules 109> stated that certain discrepancies between the fluorescence spectrum of 3-amino-phthalate dianion and the chemiluminescence spectrum of luminol are partly due to reabsorption of the shorter-wavelength chemiluminescence light by the luminol monoanion. These authors confirmed the results of E. H. White and M. M. Bursey 114> concerning the very essential solvent effect on luminol chemiluminescence the relative intensity of the latter in anhydrous DMSO/t-BuOK/ oxygen was found to be about 30,000 times that in DMSO/28 mole % water/potassium hydroxide/oxygen. 

The reaction of Ru(III) chelate with diimine is about 99 times more efficient than that of Ru(III) with hydrazine. Computer-simulated chemiluminescence time curves based on the kinetic data of the above reaction scheme exactly matched light-intensity time curves recorded in a stopped-flow spectrophotometer 166h At high hydrazine concentra-... 

As described in Chapter 3, the products of some chemical reactions are initially produced in electronically excited states. If the excited state has a sufficiently short radiative lifetime, it will emit light faster than collisional quenching by air molecules can occur (see Problem 1). The effective concentration of the emitting species (and hence emitted light intensity) is proportional to the concentrations of the reactants. As a result, the chemiluminescence intensity can be used to monitor one of the reactants if the second reactant is kept at a constant (excess) concentration. 

The chemiluminescence intensity is dependent on polymer, temperature and geometry. However, the relationship between the oxidation rate and the chemiluminescence intensity is not known and very few conclusions can be drawn from comparing light intensities between samples. In order to use chemiluminescence to determine the degree of oxidation, a correlation curve using a quantitative technique has to be constructed under the same ageing condition. 

The luminol detector is based on the sensitive chemiluminescent reaction between N02 and luminol in solution. The luminol in alkaline solution reacts with N02 to produce intensive CL centred on 425 nm. The detector cell itself is a 15 cm x 8 cm x 2 cm rectangular block, with inlets and outlets for the carrier gas and luminol flows. The reaction cell contains a fabric wick that is wetted with the luminol solution (1 x 10-4M luminol, 0.2MNa2SO3, 0.05M NaOH, 1.5 x 10 4 ethylenediaminetetraacetic acid and 0.1% surfactant). The wick is viewed by a PMT through an acrylic window, which is transparent to the chemiluminescent light at 425 nm. When a N02 peak enters the cell, a fraction of the N02 dissolves in the solution on the surface of the wick, which then reacts with luminol to ultimately yield a strong CL. The results described indicate that this detector may be successfully used for the sensitive and selective detection of any nitrogen-containing species that may thermally decompose to yield N02, with a potential use for the detection of explosives (2,4-DNT and TNT). 

For the experimental determination of the 0, it is necessary to quantify the light output of the direct chemiluminescent process. The experimental definition of the direct chemiluminescence quantum yield is given in Eq. 36, that is, the initial rate of photon production (/q ) per initial rate of dioxetane decomposition k )[D]o). Alternatively, the total or integrated light intensity per total dioxetane decomposed can be used. The /t )[Z)]o term is readily assessed by following the kinetics of the chemiluminescence decay, which is usually first order. Thus, from a semilogarithmic plot of the emission intensity vs. time, the dioxetane decomposition rate constant kjj is obtained and the initial dioxetane concentration [Z)]o is known,especially if the dioxetanes have been isolated and purified. In those cases in which the dioxetanes are too labile for isolation and purification, [/)]o is determined by quantitative spectroscopic measurements or iodometric titration. 

The chemiluminescence (intensity of light was rather weak and decreased slowly) and fluorescence spectra were recorded on a Shimadzu RF-510 spectrofluorometer. The chemiluminescence spectra (intensity of light was very strong but decreased instantly) were recorded on an Otsuka Electronics IMCPD-IIO spectro multi channel photodetector. The absorption spectra were obtained with a Shimadzu UV-240 spectrophotometer. 

Although la adsored on alumina also gave rise to chemiluminescence, the light intensity was too weak to record the emission spectrum accurately, because of the low... 

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