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Fast, high peak capacity separations in comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry

► Peak capacity and peak capacity production are significantly improved for GC×GC–TOFMS. ► A peak capacity of ∼6000 was obtained in ∼6min in a GC×GC–TOFMS separation. ► Primary column peaks were ∼600ms FWHM and secondary column peaks were ∼20ms FWHM. ► Cryo-focusing thermal injection was utilized fo...

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Bibliographic Details
Published in:Journal of Chromatography A 2012-11, Vol.1266, p.116-123
Main Authors: Fitz, Brian D., Wilson, Ryan B., Parsons, Brendon A., Hoggard, Jamin C., Synovec, Robert E.
Format: Article
Language:English
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Summary:► Peak capacity and peak capacity production are significantly improved for GC×GC–TOFMS. ► A peak capacity of ∼6000 was obtained in ∼6min in a GC×GC–TOFMS separation. ► Primary column peaks were ∼600ms FWHM and secondary column peaks were ∼20ms FWHM. ► Cryo-focusing thermal injection was utilized for a narrow injection onto the primary column. ► The instrument was applied to the separation of the headspace of warm, ground coffee beans. Peak capacity production is substantially improved for two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) and applied to the fast separation of a 28 component liquid test mixture, and two complex vapor samples (a 65 component volatile organic compound test mixture, and the headspace of warm ground coffee beans). A high peak capacity is achieved in a short separation time by selecting appropriate experimental conditions based on theoretical modeling of on-column band broadening, and by reducing the off-column band broadening by applying a narrow, concentrated injection pulse onto the primary column using high-speed cryo-focusing injection (HSCFI), referred to as thermal injection. A long, relatively narrow open tubular capillary column (20m, 100μm inner diameter (i.d.) with a 0.4μm film thickness to benefit column capacity) was used as the primary column. The initial flow rate was 2ml/min (60cm/s average linear flow velocity) which is slightly below the optimal average linear gas velocity of 83cm/s, due to the flow rate constraint of the TOFMS vacuum system. The oven temperature programming rate was 30°C/min. The secondary column (1.8m, 100μm i.d. with a 0.1μm film thickness) provided a relatively high peak capacity separation, concurrent with a significantly shorter modulation period, PM, than commonly applied with the commercial instrument. With this GC×GC–TOFMS instrumental platform, compounds in the 28 component liquid test mixture provided a ∼7min separation (with a ∼6.5min separation time window), producing average peak widths of ∼600ms full width half maximum (FWHM), resulting in a peak capacity on the primary column of ∼400peaks (at unit resolution). Using a secondary column with a 500ms PM, average peak widths of ∼20ms FWHM were achieved, thus providing a peak capacity of 15peaks on the second dimension. Overall, an ideal orthogonal GC×GC peak capacity of ∼6000peaks (at unit resolution) was achieved (or a β-corrected orthogonal peak capacity of ∼4400, at an average modulati
ISSN:0021-9673
DOI:10.1016/j.chroma.2012.09.096