Detector, atomic spectrometer thermal conductivity

Elemental composition Ba 69.58%, C 6.09%, O 24.32%. The compound is digested with nitric acid under heating and the solution is analyzed for barium by atomic absorption or emission spectrometry (see Barium). Carbon dioxide may be determined by treating a small amount of the solid with dilute HCl and analyzing the evolved gas by GC using a thermal conductivity detector or a mass spectrometer. The characteristic mass of CO2 is 44. 

Besides the universal detector systems, for example electron capture, flame ionisation and thermal conductivity usually coupled with gas chromatographic columns, various other detectors are now being used to provide specific information. For example, the gas chromatograph/mass spectrometer couple has been used for structure elucidation of the separated fractions. The mechanics of this hybrid technique have been described by Message (1984). Other techniques used to detect the metal and/or metalloid constituents include inductively coupled plasma spectrometry and atomic absorption spectrometry. Ebdon et al. (1986) have reviewed this mode of application. The type and mode of combination of the detectors depend on the ingenuity of the investigator. Krull and Driscoll (1984) have reviewed the use of multiple detectors in gas chromatography. 

With a few exceptions, most of the detectors used in GC were invented specifically for this technique. The major exceptions are the thermal conductivity detector (TCD, or katharometer) that was preexisting as a gas analyzer when GC began, and the mass spectrometer (or mass selective detector, MSD) that was adapted to accept the large volumes and the fast scan rates needed for GC peaks. Most recently, other spectroscopic techniques like IR and atomic plasma emission have been coupled to the effluent from gas chromatographs, serving as GC detectors. 

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