Design and performance evaluation of a two-stage resistively-heated thermal modulator for GC × GC

Abstract

The design and performance evaluation of a two-stage resistively-heated thermal modulator that does not use any cryogenic consumables is described. A commercially available piece of stainless-steel wall coated capillary column is used as the modulator. Cooling of the modulator is provided by a two-stage refrigeration unit with an external heat exchanger and a closed-loop recirculating air system. The modulator is resistively heated by sending a current pulse through each stage of the modulator tube. Studies evaluating the modulator trapping efficiency, cooling efficiency, desorption efficiency, and resultant peak shape are presented and discussed. Performance evaluation of this modulator is compared to similar single-stage modulators, both qualitatively and quantitatively, and has exceeded the previous data reported for the single stage versions. GC Â GC chromatograms of a C 6 -C 20 n-alkane mixture, a petroleum sample, and a 38-component mixture of aliphatic, aromatic, and halogenated volatile organic compounds are provided. This two-stage modulator proves to be a viable alternative to commercially available modulators which require large amounts of cryogenic fluids.

Opportunities and challenges for the application of post-consumer plastic waste pyrolysis oils as steam cracker feedstocks: To decontaminate or not to decontaminate?

“…Between both columns, there is a modulator which can be a valve modulator ( Sinha et al, 2003 ), thermal modulator ( Libardoni et al, 2010 , Phillips and Xu, 1995 , Beens et al, 1998a , Phillips et al, 1999 , Beens et al, 1998b , Gaines et al, 1999 ) or cryogenic modulator ( Phillips and Beens, 1999 , Kinghorn et al, 1998 , Pursch et al, 2003 ) functioning as an interface. The main purpose of the modulator is to trap adjacent fractions of the effluent, to refocus and rapidly send them to the second dimension column ( Adahchour et al, 2008 , Beens et al, 2001 , Adahchour et al, 2006 ).…”

Comprehensive two-dimensional gas chromatographic separations with a temperature programmed microfabricated thermal modulator

“…Thermal modulation (TM) entails alternately trapping 1 D peak segments by condensation, typically by bathing a short section of the (typically 2 D) capillary column in a fluid at cryogenic temperatures, and then remobilizing them by removing the fluid and/or applying a jet of hot air, which rapidly raises the temperature for passage of the segment to the 2 D column [19][20][21][22][23][24][25]. Values of fwhm as low as 20 ms have been reported by use of TM [25].…”

The Importance of Detector Acquisition Rate in Comprehensive Two-Dimensional Gas Chromatography (GC×GC)

“…Peak widths delivered by GC × GC are on the order of tens to hundreds of milliseconds (6,19). As a result, data acquisition speeds must be sufficient to ensure the proper number of data points across a band (10-20 points).…”

“…Each type of modulator has specific advantages and applications; however, for this study only thermal modulation was used. Thermal modulators use differences in temperature to change the retention factor (k value) of the trapped compound(s) during the modulation process (5,6). Column cooling essentially "traps" components in the modulator prior to a pulse of heat to release the components.…”