On retentivity tuning by flow in the second column of different comprehensive two dimensional gas chromatographic...

Retentivity tuning in comprehensive two dimensional GC separations of aliphatics (linear and cyclic hydrocarbons) and aromatics in gasoline by changing the carrier gas flows in the column series at constant working temperature parameters of both columns is discussed. Comprehensive 2D techniques studied include GC×GC with cryogenic and differential flow modulation and non-modulated transfer (NMT). In all configurations, the first dimension was a non-polar column and the second dimension a polar column. Using three different flows (0.6, 1.0 and 1.4mL/min) of helium carrier gas in cryogenic modulated GC×GC illustrated that, as expected, retention of the solutes on the (1)D and (2)D columns increased but the separation quality was nearly constant. A change of carrier gas pressure (p(m)=175-125kPa) on the (1)D and (2)D columns joint point at constant inlet pressure (p(i)=525kPa) in NMT, induces an increase of the carrier gas flow rate on the (1)D and a decrease on the (2)D column, respectively. The higher retentivity of the (2)D column improved the group type separation of aliphatic/cyclic hydrocarbons and aromatics and a higher distribution of aromatics on the 2D retention plane was noted. Retentivity tuning was also performed in flow modulated GC×GC by operating the (1)D column at 0.8mL/min and the (2)D column at 20 and 26mL/min. The higher retentivity at 20mL/min improved the group type separation of aliphatic/cyclic hydrocarbons and aromatics in the 2D retention plane.