Absorption spectra polycyclic aromatic hydrocarbon

The limit of detection (LOD) for an acceptable GC-IR response for most compotmds is between about 1 and 20 ng (injected) per component, the actual value depending on the chemical nature of the analyte. The LOD is often defined with respect to the strongest band in the spectrum. Most bands in the infrared spectrum of nonpolar compounds are fairly weak and so these compounds tend to have the highest LODs, but even these compounds usually have at least one band in the spectrum with a high absorptivity. Examples include the C-H stretching bands of alkanes and the aromatic C-H out-of-plane deformation bands of polycyclic aromatic hydrocarbons. Detection limits also depend on the width of the GC peak the wider the peak, the more dilute the analyte and the higher the LOD. 

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