Page 158 - Tandem Techniques
P. 158
Page 141
gas, the solute peaks from the column would accumulate in the IR light pipe, and as a consequence,
several solutes would be detected and measured simultaneously, and resolution would be lost. The light
pipe itself is 120 mm long, 1 mm I.D and coated internally with gold. The oven surrounding the light
pipe, can be operated up to 350°C, and is carefully designed to eliminate any cold spots on the tube,
which might allow solute condensation. After the sample has passed though the light pipe, it can be
returned to the FID in the chromatograph oven or passed to a second tandem instrument such as a mass
spectrometer. It is claimed that satisfactory spectra can be obtained from a 1-5 ng of material in the light
pipe which is supported by the spectrum shown in Figure 4.7. The spectrum from 10 ng of material,
has more than sufficient IR absorption data to allow the identity of the solute to be confirmed by
comparison with the library spectrum shown below the sample spectrum. Clearly, the system can be
used, either to aid in structure elucidation, or to confirm compound identity.
Figure 4.7
A GC/IR Spectrum of 10 ng of Isobutyl Methacrylate
