Pulsed flow modulation comprehensive two-dimensional gas chromatography

Pulsed flow modulation (PFM) is based on higher flow rate time compression of the first GC column effluent, which prior to the injection into the second column is stored for a few seconds in a standard fused silica wide bore transfer line. We constructed the PFM device with two standard 1/16 in. brass compression fittings with the insertion of the two columns inside the wide bore 0.53 mm W. fused silica storage transfer line for the elimination of dead volumes. This simple arrangement provides a combination of flexibility in the length of the sample storage transfer line hence comprehensive two-dimensional gas chromatography (GC x GC) cycle time, inert sample path and full elimination of cooling gas consumption. A record short second column injection time of 20 ms is demonstrated. Practical injection times are the sample collection time (such as 4 s) divided by the second to first column flow rate ratio (such as 20/0.7), which is typically around 150 ms. Due to the low cost of the device it can also be considered for use with non comprehensive time segmented GC x GC to remove a few accidental coelutions. PFM-GC x GC excels with high second column capacity due to the use of 0.32 mm i.d. columns with high flow rates as the second dimension GC x GC column. As a result, PFM-GC x GC can have up to two orders of magnitude higher second column sample capacity and linear dynamic range for improved reduction of adverse matrix interference effects due to column overloading. (C) 2007 Elsevier B.V. All rights reserved.