Observation of non-linear chromatographic peaks in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) often incorporat es a conventional capillary gas chromatography column in combination with a fast elution column. If this latter column has a thin stationary phase fil m, it may be supposed that the analyst risks loss of peak resolution due to the onset of non-linear conditions. This will normally be evidenced by ove rloading - or fronting - peak shapes. GC x GC methods which result from zon e compression will be even more likely to exhibit overloading on the second column since the instantaneous peak concentration (CM and Cs), will be sig nificantly greater than that of the band which enters the modulation region . Two cases of overloading may be considered - that on the first column, an d that on the second column. Each of these cases will lead to different two -dimensional peak shapes when the GC x GC result is converted to a two-dime nsional separation space. In each instance, however, resolution of componen ts will be degraded, although the GC x GC experiment will still not be as b adly affected as a single dimensional GC analysis. When overloading conditi ons are obtained, the GC x GC peak pulsing phenomenon will result in the ex tremities of the chromatographic band showing linear conditions even though the centre of the band is non-linear.