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the argon was slowly evaporated leaving the solute as a residue ready for examination. Another
procedure for improving the trapping efficiency was to retain the solute on an adsorbent contained in a
short length of packed tube. After collection, the solute was regenerated by passing a stream of gas
through the heated tube, and then it was either examined as a vapor sample, or it was bubbled through a
suitable IR solvent and the spectrum obtained in the usual manner. An adsorbent that was frequently
used for this purpose was a GC packing containing a heavy loading of a high boiling stationary phase,
such as 'Apiezon Grease'. Apiezon Grease was a proprietary vacuum grease which was very popular in
the early days of gas chromatography as a high-temperature stationary phase.
The Early GC/IR/MS Triplet System
The first automated on-line GC/IR system was described by Scott et al. [I] and involved the adsorption
of each solute in a cold packed tube, followed by its thermal desorption into an infrared vapor cell. In
fact, the instrument also provided mass spectra, the sample for the mass spectrometer being taken from
the IR cell, after the IR spectrum had been obtained.
Figure 4.1
Diagram of an Automatic GC/IR Tandem System
