Demonstrations, chemiluminescent

An alternative method for demonstrating chemiluminescence, using potassium fer-ricyanide and hydrogen peroxide as oxidizing agents, is described in E. H. Huntress, L. N. Stanley, and A. S. Parker, Journal of Chemical Education, 11 (1934) 142. 

Subsequent studies (63,64) suggested that the nature of the chemical activation process was a one-electron oxidation of the fluorescer by (27) followed by decomposition of the dioxetanedione radical anion to a carbon dioxide radical anion. Back electron transfer to the radical cation of the fluorescer produced the excited state which emitted the luminescence characteristic of the fluorescent state of the emitter. The chemical activation mechanism was patterned after the CIEEL mechanism proposed for dioxetanones and dioxetanes discussed earher (65). Additional support for the CIEEL mechanism, was furnished by demonstration (66) that a linear correlation existed between the singlet excitation energy of the fluorescer and the chemiluminescence intensity which had been shown earher with dimethyl dioxetanone (67). 

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

Alternatively, weak acids and certain salts have been found to extend the lifetimes of inherently rapid reactions which occur with highly reactive esters, such as bis(2,4-dinitrophenyl) oxalate (95). A chemiluminescent demonstration based on the oxaUc ester reaction has been described (96) and the reaction has been developed iato a practical lighting system. 

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. 

Though we and others (27-29) have demonstrated the utility and the improved sensitivity of the peroxyoxalate chemiluminescence method for analyte detection in RP-HPLC separations for appropriate substrates, a substantial area for Improvement and refinement of the technique remains. We have shown that the reactions of hydrogen peroxide and oxalate esters yield a very complex array of reactive intermediates, some of which activate the fluorophor to its fluorescent state. The mechanism for the ester reaction as well as the process for conversion of the chemical potential energy into electronic (excited state) energy remain to be detailed. Finally, the refinement of the technique for routine application of this sensitive method, including the optimization of the effi-ciencies for each of the contributing factors, is currently a major effort in the Center for Bioanalytical Research. 

This is a chronic inflammatory disease, which can affect the gut as well as other organs. There is relatively little information on the role of free radicals in this condition. Neutrophil chemiluminescence was increased in patients with intestinal Behcet s compared to normal controls (Suematsu et al., 1987a) and there is some evidence for endothelial injury by neutrophil-derived oxidants (Niwa et al., 1982). Preliminary studies with lip)osomal-encapsulated SOD demonstrated marked improvement in 12 out of 16 pjatients wdth active Behcet s disease (Niwa etal., 1985). 

Chemiluminescence has been used to demonstrate increased free-radical activity after induction of caerulein pancreatitis, with levels peaking at about 20 min and decreasing rapidly to control values thereafter (Gough et al., 1990). Electron spin resonance has been used to demonstrate increased hydroxyl radical activity in choline-deficient diet pancreatitis in the mouse (Nonaka etal., 1989a). 

Supercritical fluid chromatography (SEC) was first reported in 1962, and applications of the technique rapidly increased following the introduction of commercially available instrumentation in the early 1980s due to the ability to determine thermally labile compounds using detection systems more commonly employed with GC. However, few applications of SEC have been published with regard to the determination of triazines. Recently, a chemiluminescence nitrogen detector was used with packed-column SEC and a methanol-modified CO2 mobile phase for the determination of atrazine, simazine, and propazine. Pressure and mobile phase gradients were used to demonstrate the efficacy of fhe fechnique. 

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. 

In 1982, the Schaap group demonstrated that chemiluminescence can be induced by the addition of a base to dioxetanes bearing a phenolic substituent [11]. Herein, the same group presents a method utilizing aryl esterase to catalyze the cleavage of a naphthyl acetate-substituted dioxetane in aqueous buffer at ambient... 

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... 

The same may be observed with magnesium carbonate in cellulose [70] (Figure 26). The chemiluminescence intensity at a given temperature increases with pH of the sample almost linearly. As it is evidenced by DSC, the sample with pH 7.2 is the least stable. Figure 26 is also a demonstration of the much higher sensitivity of the chemiluminescence method when compared with DSC. DSC exotherms, which accompany the final stages of the cellulose decomposition... 

Another rather striking example demonstrates that the fluorescence efficiency of the respective dicarboxylates is not the most important factor in determining the chemiluminescence efficiencies of the hydrazides 9.10-diphenylanthracene-2.3-dicarbonic acid 25 has a fluorescence efficiency of about 0.9 (as has the parent compound 9.10-di-phenylanthracene) 94>. The corresponding hydrazide 26, however, gives a quantum yield of 48% that of luminol only (in DMSO/t-BuOK/ O2) 95) although 3-aminophtalic acid has a fluorescence efficiency of about 0.3 only. 

It is clear that when surfing on the Internet applying uniquely the keyword chemiluminescence, many important sites show up. These include principles and applications, spectroscopy, potentials in liquid chromatography, university training courses, products, demonstrations, etc. 

This compound chemiluminesces when exposed to air or oxygen. Its CL was first demonstrated by Fletcher and Heller [47, 48] and suggested to occur via formation of a dioxetane by addition of oxygen across the ethylenic double bond. Cleavage of the dioxetane to form excited tetramethylurea results in excitation of the tetrakis (dimethylamino) ethylene, whose CL is in good agreement with the fluorescence spectrum of the parent compound. The reaction has been used for the analysis of oxygen [49, 50],... 

Typically, intense chemiluminescence in the UV/Vis spectral region requires highly exothermic reactions such as atomic or radical recombinations (e.g., S + S + M - S2 + M) or reactions of reduced species such as hydrogen atoms, olefins, and certain sulfur and phosphorus compounds with strong oxidants such as ozone, fluorine, and chlorine dioxide. Here we review the chemistry and applications of some of the most intense chemiluminescent reactions having either demonstrated or anticipated analytical utility. 

SOD in Figure 5 demonstrates the effect of superoxide dismutase on PCL. Its effect is characterized by an inhibition of the chemiluminescence intensity without having an impact on the lag phase. According to McCord and Frido-vich [27] (50% test signal inhibition), 1 activity unit in this system refers to approximately 100 ng of the enzyme preparation of the Sigma Co. 

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