This would result in the adsorption curve of an early eluted solute persisting throughout the spectra of later eluted solutes. 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 1Ð5 ng of material in the light pipe, which is supported by the spectrum shown in figure 35.

The spectrum was taken from 10 ng of material, and contains more than sufficient IR absorption data to allow the identity of the solute to be confirmed. Clearly, the system can be used, either to aid in structure elucidation, or to confirm compound identity. Examples of the use of the device to identify some drugs of abuse are shown in figure 36.

The sample was separated on a GC column employing normal development techniques, and the spectra taken of the peaks as they were eluted through the light pipe. It is clear that the spectra that are obtained would be perfectly satisfactory for solute identification.