Second dimension column ensemble pressure tuning in comprehensive two-dimensional gas chromatography

A pressure tunable (PT) coupled column ensemble has been implemented for the second dimension (D-2) separation in comprehensive two dimensional gas chromatography (GCxPTGC). This process requires two columns to be connected by a pressure junction, as a replacement for a single narrow bore, short column in D-2. Various D-2(1) and D-2(2) columns may be selected to provide complementary selectivity (polarity) compared to the D-1 column. The tunable residence time arising from differential pressure drop in each D-2 column results in a tunable fractional contribution of each column in the D-2 separation. A sample mixture comprising different chemical classes, including alkanes and alcohols, is used to identify the feasibility and extent of selectivity tuning possible in GCxPTGC. The column length is also varied due to the imposed challenge of wraparound in the PT coupled column system as pressures are adjusted in the D-2 separation. Different experimental parameters, stationary phase materials and column lengths have been applied to investigate and understand the separation behaviour of the D-2 PT coupled column GCx GC system. Results are discussed considering analyte retention time, peak width, linear velocity and the contribution of each D-2 column. A specific and unexpected example of GCx GC separation was demonstrated where the peak positions of polar and apolar compounds could almost swap their D-2 retention position by application of PT. Kerosene was analysed as an example of complex sample analysis by GCxPTGC system. This process is shown to be a practical approach for altering different stationary phase selectivities in a single D-2 arrangement in GCx GC. (C) 2017 Elsevier B.V. All rights reserved.