The Atomic Emission Detector AED

Tunable, separately or simultaneously selective for compounds containing many specific atoms (e.g., C, O, N, S, P, Si, Sn, halogens, other metals) destructive mass-flow detector sensitivity and dynamic range vary with element measured (cf. Fig. 12.13). 

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One of the most attractive detectors for screening of CWC-related chemicals is the atomic emission detector (AED), which is capable of detecting selectively any element below the nanogram level. The... 

There are a number of other GC detectors commercially available. Photoionization detectors (PIDs) are primarily used for the selective, low-level detection of the compounds which have double or triple bonds or an aromatic moiety in their structures. Electrolytic conductivity detectors (ELCDs) are used for the selective detection of chlorine-, nitrogen-, or sulfur-containing compounds at low levels. Chemiluminescence detectors are usually employed for the detection of sulfur compounds. The atomic emission detectors (AEDs) can be set up to respond only to selected atoms, or group of atoms, and they are very useful for element-specific detection and element-speciation work. 

In the atomic emission detector (AED), the effluent from the GC column is introduced into a microwave-induced plasma (MIP), an inductively coupled plasma (ICP), or a direct current plasma (DCP). The MIP has been most widely used and is available commercially. The MIP is used in conjunction with a diode array or charge-coupled-device atomic emission spectrometer as shown in Figure 27-12. The pl ma is sufficiently en-... 

Such a system with an atomic emission detector (AED) for the analysis of nitrogen-chlorine- and Sulfur-containing pesticides in aqueous samples (39), as shown in Figure 2.19. 

Many sophisticated analytical techniques have been used to deal with these complex mixtures.5,45,46 A detailed description is not possible here, but it can be noted that GLC, often coupled with mass spectrometry (MS), is a major workhorse. Several other GLC detectors are available for use with sulfur compounds including flame photometer detector (FPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED).47 Multidimensional GLC (MDGC) with SCD detection has been used48 as has HPLC.49 In some cases, sniffer ports are provided for the human nose on GLC equipment. 

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. 

The atomic emission detector is a tunable, element-specific detector that uses microwave-induced helium plasma to generate temperatures high enough to break molecular bonds. The generated free atomic species undergo electron excitation to higher energy states, followed by relaxation and photon emission at characteristic frequencies... 

T.G. Albro and J. Lippert, Use of the atomic emission detector for screening and detection of chemical warfare agents and their breakdown products, in Proceedings of the 1994 ERDEC Scientific Conference on Chemical and Biological Defense Research., D.A. Berg (Ed.), National Technical Information Service, Spring-field, 171-176, 1996. 

The sulfur compounds in the FCC gasoline typically comprise mercaptans, thiophene, C1.4 substituted thiophenes, thiophenol, C1.2 substituted thiophenols, tetrahydrothiophene and benzothiophene, and are best analyzed by a Gas Chromatograph (GC) equipped with an Atomic Emission Detector (AED), Figure 5.29. 

The use of an atomic emission detector (AED) coupled to a GC may provide under ideal conditions information about the empirical formula of the analyte corresponding to a GC peak. However, it was found that the AED responses of C, Cl and O of a series of phenols is related to the working condition of the AED. The elemental response of Cl is independent of molecular structure, but those of C and O are not, probably due to formation of CO in the plasma. The O response is also affected in nitrophenols, probably due to NO2 formation. A novel detector, based upon hyperthermal negative surface ionization, shows up to 100-fold higher sensitivity than that of the FID for alcohols and phenolic compounds. ... 

Sulfur-containing components exist in gasoline-range hydrocarbons and can be identified with a gas chromatographic capillary colunm coupled with either a sulfur chemiluminescence detector or an atomic emission detector (AED) (ASTM D-5623). The most widely specified method for total sulfur content uses X-ray spectrometry (ASTM D-2622), and other methods that use ultraviolet fluorescence spectroscopy (ASTM D-5453) and/or hydrogenolysis and colorimetry (ASTM D-4045) are also apphcable, particularly when the sulfur level is low. 

To aid in the detection of sulfur and nitrogen-containing compounds, the extract was analyzed on a HP6890 gas chromatograph equipped with an atomic emission detector (AED) (Hewlett Packard, Wilmington, PA). The gas chromatograph conditions were the same as those described above. 

The gas chromatograph may be interfaced with atomic spectroscopic instruments for specific element detection. This powerful combination is useful for speci-ation of different forms of toxic elements in the environment. For example, a helium microwave induced plasma atomic emission detector (AED) has been used to detect volatile methyl and ethyl derivatives of mercury in fish, separated by GC. Also, gas chromatographs are interfaced to inductively coupled plasma-mass spectrometers (ICP-MS) in which atomic isotopic species from the plasma are introduced into a mass spectrometer (see Section 20.10 for a description of mass spectrometry), for very sensitive simultaneous detection of species of several elements. 

The first commercially available atomic emission detector (AED) was manufactured by Hewlett Packard. It allowed the detection of up to 15 elements automatically. In this instrument. 

Andersson, J. T., Polycychc aromatic sulfur heterocycles IV. Determination of polycyclic aromatic compounds in a shale oil with the atomic emission detector, J. Chromatogr. A., 693, 325-338, 1995 Thomson, J. S., Green, J. B., McWilliams, T. B., and Sturm, G. P., Analysis of Sulfur Compounds in Light Distillates, Symposium on Petroleum Chemistry and Processing, Chicago IL, 1995, pp. 696-698. 

A method for the detection of nerve agent metabolites ba,sed on GC coupled with an atomic emission detector (AED) has been reported (Creasy etal., 1995). The nerve agent degradation products were extracted from spiked water, wipes, and soil samples. The extracted samples were deriva-tized with 1% trimethylchlorosilane in bis-(trimethylsilyl) trifluoroacelamidc. The GC/AED technique was used for separation, detection, and determination of OP nerve agent metabolites. 

Other even more sjjccific detectors can also be coupled to GCxGC. Atomic emission detectors (AEDs), and more element-selective detectors, such as sulfur compound detectors (sulfur chemiluminescence detector, or SCD), have been reported in the oil characterization area [84,85]. In these detectors, the combustion of sulfur compounds by an energetic induced plasma produces sulfur oxides that further react to and produce light at a specific wavelength that... 

However, owing to recent developments in highly efficient separation columns for GC, and various powerful hyphenated identification techniques for GC such as GC/MS, GC/FTIR, and GC/atomic emission detector (AED), Py-GC has made great strides toward becoming a powerful tool for the structural characterization of polymeric materials. Therefore, Py-GC, in particular Py-GC/MS, now plays a very important role among various methods developed in the field of analytical pyrolysis. 

The detectors most frequently used for GC analysis of cuticular waxes are the flame ionization detector (FID) and mass spectrometer (MS) (Evershed, 1992a Hamilton, 1995b Riederer Muller, 2006). Occasionally, other detectors can be applied. For example. Gross Raphel (2003) used GC coupled to an atomic emission detector (AED) for the identification of a series of 1-chloro-n-alkanes in the leaf waxes of three halophytes. 

Element selective detectors Element selective detectors applicable in pesticide residue analysis include electron capture detector (ECD), electrolytic conductivity detector (ELCD), halogen-specific detector (XSD), nitrogen phosphorus detector (NPD), flame photometric detector (FPD), pulsed flame photometric detector (PEPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED). To cover a wider range of pesticide residues, a halogen-selective detector (ECD, ELCD, XSD) in conjvmction with a phosphorus- (NPD, FPD), nitrogen- (NPD), and/or sulfur-selective detector (FPD, SCD) is commonly used. A practical approach is to spht the column flow to two detectors that reduces the number of injections however, the reduced amoimt of analyte that reaches the detector must be considered. 

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