Emissivity detector

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. 

Johnson, D., Quimby, B., and Sullivan, J. Atomic emission detector for GC. American Laboratory, October, 13, 1995. 

AED Atomic emission detector Atomic emission spectroscopy... 

Plasmas compare favourably with both the chemical combustion flame and the electrothermal atomiser with respect to the efficiency of the excitation of elements. The higher temperatures obtained in the plasma result in increased sensitivity, and a large number of elements can be efficiently determined. Common plasma sources are essentially He MIP, Ar MIP and Ar ICP. Helium has a much higher ionisation potential than argon (24.5 eV vs. 15.8 eV), and thus is a more efficient ionisation source for many nonmetals, thereby resulting in improved sensitivity. Both ICPs and He MIPs are utilised as emission detectors for GC. Plasma-source mass spectrometry offers selective detection with excellent sensitivity. When coupled to chromatographic techniques such as GC, SFC or HPLC, it provides a method for elemental speciation. Plasma-source detection in GC is dominated by GC-MIP-AES... 

Although the data generated by a MIP emission detector for GC are similar in many ways to those produced by a mass-selective detector, the information provided is often complementary [68]. An AES detector provides ... 

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. 

A new method for Sn, Pb and Hg organometaHics is now under evaluation by the US Environmental Protection Agency. It consists of measuring the pentylated Grignard derivatives by a capillary GC-atomic emission detector LOD 1-2.5 Xg/L for 0.5 p L on column injection, with good linearity in the 2.5-2500 pg/L range129. 

Wylie, P.L. and Quimby, B.D. (1989) Applications of gas chromatography with an atomic emission detector. J. High Resol. Chromatogr. 12, 813-818. 

Atomic emission detector (AED) Atomic emission of elements 0.1-50 pg/s 4 Element selective as in atomic emission spectrometry... 

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. 

Atomic emission detectors (AEDs) and mass selective detectors (MSDs) are also being used to enhance selectivity and sensitivity for air analyses (Yamashita et al. 1992). 

There are many GC detectors available although the flame ionisation detector remains the most widely used and the most widely applicable to quality control of pharmaceutical products. However, newer detectors such as the plasma emission detector for analysis of trace impurities or the GC-FTIR detector for the structural characterisation of components in mixtures are becoming increasingly important. 

Thermionic Emission detector (e) Fused Silica (very high purity glass)... 

Lee SM, Wylie PL. 1991. Comparison of the atomic emission detector to other element-selective detectors for the gas chromatographic analysis of pesticide residues. J Agric Food Chem 39 2192-2199. 

Wylie PL, Oguichi R. 1990. Pesticide analysis by gas chromatography with a novel atomic emission detector. J Chromatogr 517 131-142. 

Mulligan KJ, Caruso JA. 1980. Determination of polybrominated biphenyl and related compounds by gas - liquid chromatography with a plasma emission detector. Analyst 105 1060-1067. 

Eluate from a chromatography column can be passed through a plasma to atomize and ionize its components and measure selected elements by atomic emission spectroscopy or mass spectrometry. An atomic emission detector directs eluate through a helium plasma in a microwave cavity. Every element of the periodic table produces characteristic emission that can be detected by a photodiode array polychromator (Figure 20-14). Sensitivity for sulfur can be 10 times better than the sensitivity of a flame photometric detector. 

The procedures used to determine ambient carbonyl concentrations involve a collection step with silica or C18 cartridges impregnated with 2,4-dinitrophenylhydrazine. Contamination is inevitable with this system, and blanks must be used to compensate for the degree of contamination. Selection of the appropriate blank values to subtract is a difficult and uncertain process. Consequently, development of a gas chromatographic system that will resolve and respond to the low-molecular-weight aldehydes and ketones is needed. The mercuric oxide and atomic emission detectors should provide adequate response for the carbonyls. 

The advantages of the flame emission detector (FED) have been combined with the flame ionization detector. This design features the ability to detect CO, CO2, N2O4, SO2, N2F4, HF and H2S gases which respond poorly in an FID. In addition, the system showed qualitative differences in structure attributable to different FED/FID ratios as a function of wavelength for various compounds. 

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