Gas Chromatography - Tandem Techniques - Modern GC/IR Systems > Light Pipe Interfaces > Page 51


Apparently, it has been claimed that spectra have been obtained from as little as 10 ng of material that provide adequate resolution and signal-to-noise for solute identification. It should be noted, that the minimum sample size that can provide adequate data, will depend strongly on the extinction coefficient of the solute at the critical adsorption wavelengths Another application of the GC/IR combined system is shown in figure 39. The chromatogram, obtained from the analysis of gasoline, was taken in the usual way by integrating the absorption curve and plotting the integral against time.


The separation was carried out on a capillary column 250 mm I.D., and the low effective volume of the light pipe allowed scan rates of up to 20 scans per second to be used. This ensured that even the very narrow peaks could be monitored without apparent distortion.



Courtesy of the Perkin Elmer Corporation


Figure 39. Chromatogram of Gasoline Monitored by IR Absorbance