Factors affecting peak shape in comprehensive two-dimensional gas chromatography with non-focusing modulation

In the case of a non-focusing modulator for comprehensive two-dimensional gas chromatography (GC x GC), the systematic distortions introduced when the modulator loads the second-dimension column give rise to a characteristic peak shape. Depending on the operating conditions this systematic distortion can be the dominant component of the second-dimension elution profiles in the GC x GC peak. The present investigation involved a systematic investigation of peak shape in pulsed-flow modulation (PFM)-GC x GC. It is shown that low flow ratio can lead to significant peak skewing and increasing the flow ratio reduces the magnitude of peak skewing. Validation of the peak shape model is made by comparison with experimental data. The residuals from the fitting process (normalised to the maximum detector response) vary between -1.5% and +2.6% for an isothermal model and between -1.0% and +3.0% for a temperature-programmed model.