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products to pass back through the burning zone after they had been formed and were thus subject to
further reaction or oxidation. Comparing the retention times of the peaks in the forward and reverse
burn chromatograms (Figure 6.17) it is clear that very different compounds are formed in the two
methods of burning. The peaks that are starred in the reverse burn chromatogram have the same
retention times as the two large peaks, Fl and F2, in the forward burn chromatogram. By treating
samples of the condensate with different reagents, that would remove compounds of specific chemical
types, and re-running the treated sample, the peaks resulting from particular selenium compounds could
be identified. This type of application gives some idea of the diverse ways in which tandem instruments
can be utilized.
Figure 6.17
Separation of the Volatile Selenium
Products from Coal Gasification
Forbes et al. [14] coupled the atomic emission spectrometer that utilized an ICP torch to a supercritical
fluid chromatograph and demonstrated its efficacy for monitoring the separation of some silicon
compounds. Their chromatograph/emission spectrometer tandem combination was very
