Peak amplitude and resolution in comprehensive gas chromatography using valve modulation

Comprehensive two‐dimensional gas chromatography (GC×GC) allows major increases in peak capacity in comparison with separations on a single column. Interfacing the two columns in GC×GC has most often been achieved by thermal modulation. However, analyte transfer by valve modulation, in which fractions from the first column are introduced into the second column by means of a multi‐port valve, is also possible. In this paper we develop a previous model of peak amplitude enhancement to compare the sensitivity and resulting resolution possible in GC×GC with thermal and valve modulation. While the peak amplitude resulting from valve modulation is inevitably much less than in thermal modulation, there is still an enhancement in comparison to single column GC. Resolution ( R ) in GC×GC with the two modulation methods has also been compared and is predicted to be generally improved for the valve modulation of partially resolved ( R = 1) narrow peaks from the first dimension column. A comparison of peak amplitude enhancement and retained resolution using thermal and valve modulation methods is made using the example of GC×GC analysis of gasoline vapour.