Flame emission detector

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. 

Overfield, C. V., Winefordner, J. D. Selective indium halide flame emission detector - potentially useful detector for gas chromatography. J. Chromatog. Sci. 8, 233 (1970). 

Several other methods have been reported for the analysis of tetraalkylleads in gasoline using gas chromatography. The methods of detection included an electron capture detector >a flame-emission detector, and a hydrogen-rich flame ionization detector. An atomic-absorption spectrometer has been used as a detector for GC391. 

Other Detectors Two additional detectors are similar in design to a flame ionization detector. In the flame photometric detector optical emission from phosphorus and sulfur provides a detector selective for compounds containing these elements. The thermionic detector responds to compounds containing nitrogen or phosphorus. 

The flame ionization detector is capable of measuring only gaseous hydrocarbons, in other words, hydrocarbons that have a low boiling point. Emission gases can, however, also contain hydrocarbons in liquid form at ambient temperature and pressure. Therefore, analyzers based on flame ionization detection are generally equipped with heating elements to keep rhe sampling line and the detector at about 200 °C. 

With flame emission spectroscopy, the detector response E is given by the expression... 

A schematic diagram showing the disposition of these essential components for the different techniques is given in Fig. 21.3. The components included within the frame drawn in broken lines represent the apparatus required for flame emission spectroscopy. For atomic absorption spectroscopy and for atomic fluorescence spectroscopy there is the additional requirement of a resonance line source, In atomic absorption spectroscopy this source is placed in line with the detector, but in atomic fluorescence spectroscopy it is placed in a position at right angles to the detector as shown in the diagram. The essential components of the apparatus required for flame spectrophotometric techniques will be considered in detail in the following sections. 

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... 

Applications Atomic emission spectrometry has been used for polymer/additive analysis in various forms, such as flame emission spectrometry (Section 8.3.2.1), spark source spectrometry (Section 8.3.2.2), GD-AES (Section 8.3.2.3), ICP-AES (Section 8.3.2.4), MIP-AES (Section 8.3.2.6) and LIBS. Only ICP-AES applications are significant. In hyphenated form, the use of element-specific detectors in GC-AED (Section 4.2) and PyGC-AED deserves mentioning. 

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. 

Tin compounds are converted to the corresponding volatile hydride (SnH4, CH3 SnH3, (CH3 )2 SnH2, and (CH3 >3 SnH) by reaction with sodium borohydride at pH 6.5 followed by separation of the hydrides and then atomic absorption spectroscopy using a hydrogen-rich hydrogen-air flame emission type detector (Sn-H band). 

The chemiluminescent reaction with chlorine dioxide provides a highly sensitive and highly selective method for only two sulfur compounds, hydrogen sulfide and methane thiol [81]. As in the flame photometric detector (FPD), discussed below, atomic sulfur emission, S2(B3S -> ) is monitored in the wave-... 

The most commonly used and widely marketed GC detector based on chemiluminescence is the FPD [82], This detector differs from other gas-phase chemiluminescence techniques described below in that it detects chemiluminescence occurring in a flame, rather than cold chemiluminescence. The high temperatures of the flame promote chemical reactions that form key reaction intermediates and may provide additional thermal excitation of the emitting species. Flame emissions may be used to selectively detect compounds containing sulfur, nitrogen, phosphorus, boron, antimony, and arsenic, and even halogens under special reaction conditions [83, 84], but commercial detectors normally are configured only for sulfur and phosphorus detection [85-87], In the FPD, the GC column extends... 

VDU screen via suitable electronic amplifying circuitry where the data are presented in the form of an elution profile. Although there are a dozen or more types of detector available for gas chromatography, only those based on thermal conductivity, flame ionization, electron-capture and perhaps flame emission and electrolytic conductivity are widely used. The interfacing of gas chromatographs with infrared and mass spectrometers, so-called hyphenated techniques, is described on p. 114 etseq. Some detector characteristics are summarized in Table 4.11. 

Chromatographic methods have been applied with hydridization. Jackson et al. [98] used a commercial purge and trap apparatus fitted to a packed gas chromatographic column and flame photometric detector to achieve a O.lng detection. Purge and trap procedures followed by boiling point separations and detection by spectrophotometric methods yield detection limits in water of between 0.01 and lng. Detection of SnH emission by flame emission gives the greatest sensitivity. 

The optical path for flame AA is arranged in this order light source, flame (sample container), monochromator, and detector. Compared to UV-VIS molecular spectrometry, the sample container and monochromator are switched. The reason for this is that the flame is, of necessity, positioned in an open area of the instrument surrounded by room light. Hence, the light from the room can leak to the detector and therefore must be eliminated. In addition, flame emissions must be eliminated. Placing the monochromator between the flame and the detector accomplishes both. However, flame emissions that are the... 

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