Page 171 - Tandem Techniques
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The configuration consists of a Perkin Elmer Model 7 thermogravimetric analyzer coupled to a standard
Hewlett-Packard GC/IR/MS system. A heated transfer line directly couples the TGA to the gas
chromatograph, by means of a special injection system that will be described below. The furnace was
maintained at a pressure of 0.14 bar above atmospheric pressure, to drive the decomposition gases and
vapors through the conduit to the sampling device. A specimen of the vapors, produced during the
thermogravimetric analysis, is periodically taken during the heating program. The sample is separated
on the capillary column and the exit gas is split into two streams. One stream goes directly to the FTIR
spectrometer and the other to the mass spectrometer. In this way a total ion current chromatogram
and/or a total IR absorption chromatogram can be generated in real time or, if preferred, can be
reconstructed after the analysis is completed. In addition, IR and MS spectra from any selected peak can
be generated from disc for identification purposes. The constituents are identified and quantitatively
assayed from their spectra. Identification can be achieved by direct comparison with reference spectra,
or by elucidating the structure from the data provided by the complementary IR and MS spectra.
Figure 4.20
Diagram of the Automatic Vapor Sampler
