Reaction with ozone chemiluminescence

Nickel Carbonyl The extremely toxic gas nickel carbonyl can be detected at 0.01 ppb by measuring its chemiluminescent reaction with ozone in the presence of carbon monoxide. The reaction produces excited nickel(II) oxide by a chain process which generates many photons from each pollutant molecule to permit high sensitivity (315). 

Chemiluminescence. Chemiluminescence (262—265) is the emission of light duting an exothermic chemical reaction, generaUy as fluorescence. It often occurs ia oxidation processes, and enzyme-mediated bioluminescence has important analytical appHcations (241,262). Chemiluminescence analysis is highly specific and can reach ppb detection limits with relatively simple iastmmentation. Nitric oxide has been so analyzed from reaction with ozone (266—268), and ozone can be detected by the emission at 585 nm from reaction with ethylene. 

Chemiluminescent techniques have been used to determine nanomolar quantities of nitrate and nitrite in seawater [124,125]. This method depends on the selective reduction of these species to nitric oxide, which is then determined by its chemiluminescent reaction with ozone, using a commercial nitrogen oxides analyser. The necessary equipment is compact and sufficiently sturdy to allow shipboard use. A precision of 2nmol/l is claimed, and an analytical range of 2nmol/l with analysis rates of 10-12 samples hourly. 

In the chemiluminescent detection of nitrogen oxides, a constant source of ozone reacts with a metered air sample containing nitric oxide. Fontijn et al. suggested that this method could also be used for ozone detection by using a constant nitric oxide source for reaction with ozone in the air sample. The ozone-nitric oxide reaction is carried out at reduced pressure, to avoid quenching the chemiluminescent reaction. Detection of the emission in the spectral r on involved (600-3,000 nm) requires using a near-infrared-sensitive photomultiplier tube. The noise of such a photomultiplier tube is reduced by cooling it to about - 20 C. ... 

Bound nitrogen includes all nitrogen-containing compounds, except N2, dissolved in water. Kjeldahl nitrogen analysis, described in Section 7-2, is excellent for amines and amides but fails to respond to many other forms of nitrogen. An automated combustion analyzer converts almost all forms of nitrogen in aqueous samples into NO, which is measured by chemiluminescence after reaction with ozone 17... 

An alternative to FPD in the sulfur mode is the sulfur chemiluminescence detector (SCD) (48). This detector works by forming sulfur monoxide in a reducing flame. Sulfur monoxide is detected by its chemiluminescent reaction with ozone. The SCD is at least one order of magnitude more sensitive than most FPDs. It provides a linear response with high selectivity and does not suffer considerably from quenching. 

Detection of NO. Nitrogen monoxide, dried on a magnesium perchlorate trap, is detected after reaction with ozone by the chemiluminescence produced by excited N02 molecules coming back to ground state. Parks and Marietta (13) and Drushell (14) were the first to use this method for nitrogen determination. The detector used in this... 

Several commercial analyzers for the determination of gases are based on chemiluminescence. Nitric oxide (NO) can be determined by reaction with ozone (O3). The reaction converts the NO to excited NO2, with the subsequent emission of light. 

Chemiluminescence detectors possess considerable selectivity for nitrosamines because the light emitted from the NO-ozone reaction is in the near infrared region, whereas other known chemiluminescent reactions with ozone emit light in the visible or near UV region (17,20,26,27). An optical filter eliminates response to emissions occurring below 600 nanometers. Selectivity is additionally provided by a cold trap between the pyrolysis chamber and the NO-ozone reaction chamber which removes all but... 

Figure 1 Ozone-mediated chemiluminescence detector. The chromatographic effluent reacts with oxygen or a reagent gas In the furnace. The excited-state species Is generated by reaction with ozone, and the emission Is detected by a photomultiplier tube (PMT).

The concentration of nickel carbonyl in air can be determined using the chemiluminescence reaction with ozone and purified carbon monoxide (reaction [VIII]). The emission intensity is measured at 500nm and the detection limit is 2ppbv ... 

The chemiluminescent detector is a mass-sensitive detector, which is highly selective for either sulfur (SCD) or nitrogen (NCD), depending on the instrumentation. The mechanism of detection is a two-step process with initial combustion followed by low-pressure reaction with ozone. The oxidation products emit a characteristic light, which is measured. The detection limit is about 0.5pgSs and 3 pg N s and the linearity is 10". One main use is the determination of sulfur compounds in petrochemical products. 

Light emitted by oxidation reactions with ozone leads to the most numerous applications of chemiluminescence. A common example of CL in the gas phase is the reaction of nitric oxide with ozone ... 

O ne. Air pollution (qv) levels are commonly estimated by determining ozone through its chemiluminescent reaction with ethylene. A relatively simple photoelectric device is used for rapid routine measurements. The device is caHbrated with ozone from an ozone generator, which in turn is caHbrated by the reaction of ozone with potassium iodide (308). Detection limits are 6—9 ppb with commercially available instmmentation (309). 

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). 

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]. 

The chemiluminescent reaction of SO with ozone is the basis of the sulfur chemiluminescence detector (SCD) [23] discussed later in this chapter,... 

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