Detector flame heated cell

Elements such as As, Se and Te can be determined by AFS with hydride sample introduction into a flame or heated cell followed by atomization of the hydride. Mercury has been determined by cold-vapour AFS. A non-dispersive system for the determination of Hg in liquid and gas samples using AFS has been developed commercially (Fig. 6.4). Mercury ions in an aqueous solution are reduced to mercury using tin(II) chloride solution. The mercury vapour is continuously swept out of the solution by a carrier gas and fed to the fluorescence detector, where the fluorescence radiation is measured at 253.7 nm after excitation of the mercury vapour with a high-intensity mercury lamp (detection limit 0.9 ng I l). Gaseous mercury in gas samples (e.g. air) can be measured directly or after preconcentration on an absorber consisting of, for example, gold-coated sand. By heating the absorber, mercury is desorbed and transferred to the fluorescence detector. 

A conventional gas chromatograph equipped with the appropriate detector (e.g., flame ionization, thermal conductivity, etc.) depending on the reactant(s) and product(s). A separation column, L, may also be incorporated in the GC oven. The separation column can be filled with the appropriate material for the separation of the reactants and products, and it can be heated in the same or at a different temperature from the sampling cell. 

Fig. 3.3A illustrates a typical design of a glass pyrolytic cell [37]. Similar cells were described by Janak [38], Jones and Moyles [39, 40] and Mlejnek [41]. They have also been used by other investigators. To increase the concentration of the resulting products and use a simpler thermal conductivity detector. Franc and Blaha [42] employed platinum mesh as the pyrolytic cell filament. This enabled them to increase the sample size without increasing the weight of the polymer under investigation per unit area of the heated filament surface, so that they could use a thermal conductivity detector instead of a flame-ionization detector. 

The experimental arrangement involved in an AES measurement is shown in Fig. IE. The hot analyte environment, which is able to break down and excite atoms, is called an atom cell. The atom cell can be a flame, plasma, a heated graphite tube, or any other environment where the analyte is observed in a spatially confined arrangement. In Fig. I, the detector box is used to represent a detection system, which is able to identify the wavelength and measure the intensity of the emitted radiation. The experimental arrangement is the simplest of the three optical atomic spectrometric techniques. 

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