9 Data Analysis
GC Image Basic Information
2D-LC User Guide 272
5 Compare the separations resulting from using the same second dimension
gradient (from 5 – 95 % and also from 25 – 75 % B) repeating during the
whole run to the separation obtained using continuously shifted second
dimension gradients in the checkout run.
Notice how the peaks are slightly further separated in the second dimension
compared to using repeating gradients from 5 – 95 % B. Also notice that the last
peaks eluting from the first dimension column are not eluted in one modulation
cycle from the second dimension column (wrap-around; see marked area).
To be able to use even shallower gradients in the second dimension to further
improve the separation and to also avoid the occurrence of wrap-around,
continuously shifted gradients can be used in the second dimension (as was
done during the checkout runs).
Notice how the peaks are spread more widely across the two-dimensional
separation space (the accessible two-dimensional separation space is enlarged)
when shifted gradients are used. Also, notice the effect that using continuously
shifted second dimension gradients has on the second dimension retention
times of consecutive fractions of the same first dimension peak.
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