Emission-detected

Atomic Emission Detection Limits for Selected Elements... 

Oxygen and nitrogen also are deterrnined by conductivity or chromatographic techniques following a hot vacuum extraction or inert-gas fusion of hafnium with a noble metal (25,26). Nitrogen also may be deterrnined by the Kjeldahl technique (19). Phosphoms is determined by phosphine evolution and flame-emission detection. Chloride is determined indirecdy by atomic absorption or x-ray spectroscopy, or at higher levels by a selective-ion electrode. Fluoride can be determined similarly (27,28). Uranium and U-235 have been determined by inductively coupled plasma mass spectroscopy (29). 

Figure 2.19 Schematic representation of an on-line liquid-liquid extraction-GC/AED system. Reprinted from Journal of High Resolution Chromatography, 18, E. C. Goosens et al, Continuous liquid-liquid extraction combined on-line with capillary gas chromatography- atomic emission detection for environmental analysis , pp. 38-44, 1995, with permission from Wiley-VCH.

Janak K, G Becker, A Colmsjo, C Ostman, M Athanasiadou, K Valters, A Bergman (1998) Methyl sulfonyl polychlorinated biphenyls and 2,2-bis(4-chlorophenyl)-l,l-dichloroethene in gray seal tissues determinated by gas chromatography with electron capture detection and atomic emission detection. Environ Toxicol Chem 17 1046-1055. 

The presence of heteroatoms usually provides a convenient feature for improving selectivity by employing selective detection mechanisms. GC may then use flame photometric detection (FPD) for S and P atoms and to a certain extent for N, Se, Si etc. thermoselective detection (TSD) and nitrogen-phosphorus detection (NPD) for N and P atoms electron capture detection (ECD) for halogen atoms (E, Cl, Br, and 1) and for systems with conjugated double bonds and electron-drawing groups or atomic emission detection (AED) for many heteroatoms. 

The most widely regarded approach to accomplish the determination of as many pesticides as possible in as few steps as possible is to use MS detection. MS is considered a universally selective detection method because MS detects all compounds independently of elemental composition and further separates the signal into mass spectral scans to provide a high degree of selectivity. Unlike GC with selective detectors, or even atomic emission detection (AED), GC/MS may provide acceptable confirmation of the identity of analytes without the need for further information. This reduces the need to re-inject a sample into a separate GC system (usually GC/MS) for pesticide confirmation. Through the use of selected ion monitoring (SIM), efficient ion-trap or quadrupole devices, and/or tandem mass spectrometry (MS/MS), modern GC/MS instruments provide LODs similar to or lower than those of selective detectors, depending on the analytes, methods, and detectors. 

On the whole, the applications of plasma-source emission detection to GC in the field of polymer/additive analysis are limited. The same holds for GC-atomic absorption spectrometry [370]. 

With the exception of GC-MIP-AES there are no commercial instruments available for speciation analysis of organometallic species. Recently, a prototype automated speciation analyser (ASA) for practical applications was described [544,545], which consists of a P T system (or focused microwave-assisted extraction), multicapillary GC (MC-GC), MIP and plasma emission detection (PED). MCGC-MIP-PED provides short analysis times ([Pg.676]

NQR Nuclear quadrupole resonance PED Plasma emission detection... 

Three different detection methods (gas chromatography with electron capture, mass spectrometric and atomic emission detectors) have been compared for the determination of polychlorobiphenyls in highly contaminated marine sediments [74], Only atomic emission detection in the chlorine-selective mode provided excellent polychlorobiphenyl profiles without interferences. However, the lower sensitivity of the atomic emission detector, compared to the other two detectors required a 10 to 20g sample size for most analyses. 

Direct monitoring of the catalysed reaction has most usually been carried out in real time by light absorption or fluorescent emission analysis and some initial progress has been made with light emission detection. The low quantity of abzyme usually available at the screening stage puts a premium on the sensitivity of such methods. However, some work has been carried out of necessity using indirect analysis, e.g. by hplc or nmr. 

A method with LOQ at ppt levels was developed based on LLE followed by GC-AFID for the determination of trace concentrations of nitrobenzene, l-chloro-2-nitrobenzene and synthetic fragrances such as musk xylene (223) and musk ketone (224). The method was applied to study the distribution of these compounds in environmental samples of North Sea waters460. GC with atomic emission detection (AED) has been successfully applied to the determination of nitro musks in human adipose tissues, at ppb concentration levels. A clean-up procedure for nonpolar substances and element-specific detection with AED enabled for the first time target screening analysis for lipophilic nitro aromatic compounds. The lack of sensitivity of AED was compensated by higher concentrations of the extracts... 

The intensity of the fluorescence emission detected at the photodetector stage was plotted as a function of temperature over the same range, and this is shown in Figure 11.22. It falls off rapidly with temperature increase over the whole temperature region. This does not contradict the experimental evidence of Burns and Nathan(56) who showed that the fluorescence quantum efficiency of the ruby fluorescence integrated over the entire band from 620 to 770 nm is independent of temperature (to 5%) in the region from-196 to 240°C, for the emission detected here is only the A-line part of the total fluorescence emission. 

Organotin compounds enriched from a diethylether extract of a snow sample collected from the city of Gdansk, Poland and analyzed are shown in Fig. 22 b, c [286]. Gas chromatography with atomic emission detection (GC-AED) run in the chlorine and tin channels, respectively, revealed the presence of tributyltin chloride and this was subsequently confirmed by GC-MS and GC-AED analyses of an internal standard solution (e.g., 1-chlorooctane) of that compound. Quantification was based on the response to chlorine (wavelength 479 nm) in the AED system, and a detection limit of 0.5-1 ng/1 was achieved for all the reference substances. 

Galvanostatic current-pulse method, 38 29, 33 Galvanostatic technique hydrocarbon adsorption, 30 256 surface coverage, 30 299-300 Gamma emission, 26 124, 125, 127 Garin-Gault mechanism, 30 20, 23 Gas chromatography -atomic emission detection... 

Nitrogen compounds in middle distillates can be detected selectively by chemiluminescence. Individual nitrogen compounds can be detected down to 100 ppb nitrogen. Gas chromatography with either sulfur chemiluminescence detection or atomic emission detection has been used for sulfur-selective detection. 

Schematic diagram of a gas chromatography atomic emission detection (GC-AED) instrument.

Eisert R, Levsen K, Wuensch G. 1994. Element-selective detection of pesticides by gas chromatography atomic-emission detection and solid-phase microextraction. J Chromatogr 683(1) 175-183. 

Hankemeier TH, Louter AJH, Rinkema FD, et al. 1995. On-line coupling of solid-phase extraction and gas chromatography with atomic emission detection for analysis of trace pollutants in aqueous samples. Chromatographia 40(3-4) 119-124. 

Thus, the addition of a few drops of acetone to a previously irradiated solid led to an intense yellow emission, visible to the human eye for a few seconds. This emission was the same as the lower energy emission detected in the solid state. Several other liquids such as chloroform, dichloromethane, toluene, methanol, hexane or even water produced the same phenomenon and the intensity of the emission depended... 

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