Chemiluminescence gas phase

Spectra from the chemiluminescent gas phase reactions at 0,5 torr, of ozone with ethylene, tetramethylethylene, trans-2-hutene, and methyl mercaptan at room temperature are presented, and a summary of the general features of the emissions obtained from reaction in the gas phase of ozone with fourteen different olefins is given. The emitting species in the ozone-olefin reactions have been tentatively identified as electronically excited aldehydes, ketones, and a-dicarbonyl compounds. The reaction of ozone with hydrogen sulfide, methyl mercaptan, and dimethylsulfide produces sulfur dioxide in its singlet excited state. 

A report has appeared of the chemiluminescent gas-phase si lame-ozone system which incorporates a MO study supporting the conclusion that the importamt emitting species is H2SiO. Reaction of atomic oxygen with Me SiH has been investigated by... 

See also Atomic Emission Spectrometry Microwave-Induced Plasma. Chemiluminescence Gas-Phase. Derivatization of Analytes. Gas Chromatography Mass Spectrometry Fourier Transform Infrared Spectroscopy. 

Dioxetane decomposition has also been proposed to account for chemiluminescence from other reactions (43), including gas-phase reactions of singlet oxygen with ethylene and vinyl ethers (53). 

Gas-phase chemiluminescence is illustrated by the classic sodium—chlorine cool flame (174) ... 

Intense sodium D-line emission results from excited sodium atoms produced in a highly exothermic step (175). Many gas-phase reactions of the alkafl metals are chemiluminescent, in part because their low ioni2ation potentials favor electron transfer to produce intermediate charge-transfer complexes such as [Ck Na 2] (1 )- There appears to be an analogy with solution-phase electron-transfer chemiluminescence in such reactions. 

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Chemiluminescent analyzers are based on the light (chemiluminescence) emitted in the gas-phase reaction of ozone with ethylene, which is measured with a photomultipHer tube. The resulting current is proportional to the ozone concentration (see Luminescent materials, chemiluminescence). 

Nowadays all over the world considerable attention is focused on development of chemical sensors for the detection of various organic compounds in solutions and gas phase. One of the possible sensor types for organic compounds in solutions detection is optochemotronic sensor - device of liquid-phase optoelectronics that utilize effect of electrogenerated chemiluminescence. In order to enhance selectivity and broaden the range of detected substances the modification of working electrode of optochemotronic cell with organic films is used. Composition and deposition technique of modifying films considerably influence on electrochemical and physical processes in the sensor. 

Another approach to the determination of surface kinetics in these systems has been to combine molecular beams in the 10 2-10 1 mbar pressure range with the use of the infrared chemiluminescence of the C02 formed during steady-state NO + CO reactions. This methodology has been used to follow the kinetics of the reaction over Pd(110) and Pd(l 11) surfaces [49], The activity of the NO + CO reaction on Pd(l 10) was determined to be much higher than on Pd(lll), as expected based on the UHV work discussed in previous sections but in contrast with result from experiments under higher pressures. On the basis of the experimental data on the dependence of the reaction rate on CO and NO pressures, the coverages of NO, CO, N, and O were calculated under various flux conditions. Note that this approach relied on the detection of the evolution of gas-phase... 

Then, the collisional interactions with rare-gas atoms result in the formation of electronically excited alkali-metal/rare-gas molecules. These van der Waals molecules emit light. Lepoint-Mullie et al. claimed that the site of SL from alkali-metal atoms is in the gas phase inside bubbles and that the SL is chemiluminescence. 

General books [213-217], chapters [218], and reviews were published in the 1980s reporting the suitability of CL and BL in chemical analysis [219-222], the specific analytical applications of BL [223], the CL detection systems in the gas phase [224], in chromatography [225, 226], the use of different chemiluminescent tags in immunoassay, and applications in clinical chemistry [227-232] as well as the applications of CL reactions in biomedical analysis [233]. 

A Fontijn, ed. Gas-Phase Chemiluminescence and Chemi-Ionization. New York Elsevier, 1985. 

Sievers Instruments. Gas-phase chemiluminescence detector http / / www.SieverInst.com/... 

As in the condensed phase, gas-phase chemiluminescence consists of a chemical reaction forming an excited-state product that then undergoes one or more relax-... 

As shown schematically in Figure 1, a gas-phase chemiluminescence detector consists of a reaction chamber, inlets for the analyte and reagent gas streams, a vacuum pump to lower the pressure in the reaction chamber (typically to a few torr), and a transducer such as a photomultiplier tube (PMT) to monitor the light produced in the reaction. The reagent gas, usually present in large excess, reacts with a trace concentration of analyte to produce an excited product that subse-... 

Figure 1 Schematic diagram of a generalized gas-phase chemiluminescence detector.

Optimization strategies and a number of generalized limitations to the design of gas-phase chemiluminescence detectors have been described based on exact solutions of the governing equations for both exponential dilution and plug-flow models of the reaction chamber by Mehrabzadeh et al. [12, 13]. However, application of this approach requires a knowledge of the reaction mechanism and rate coefficients for the rate-determining steps of the chemiluminescent reaction considered. 

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]. 

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