title: High temperature diaphragm valve-based comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.
abstract: A high temperature diaphragm valve-based two-dimensional (2D) gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS) instrument, with the valve mounted directly in the GC oven, is demonstrated with separations up to 325°C. Use of the diaphragm valve allowed for the use of uncoupled carrier gas flows for1D (first column dimension) and2D (second column dimension), with a1D flow rate of 1ml/min, and a2D flow rate 3ml/min. The 3ml/min flow rate on2D was selected to ensure compatibility with most TOFMS detectors. For valve-based modulation, a 5µl sample loop coupled with a 60ms pulse width was selected, providing sufficient sensitivity concurrent with an acceptable2D peak capacity. A 44-component mixture of alkanes, alcohols, and polyaromatic hydrocarbons (including n-alkanes of heptane to triacontane) whose boiling points range from 98°C to 450°C was used to initially study instrument performance. For a 120min separation and a modulation period PMof 2s, average peak widths-at-base of 10s and 94ms were achieved for the alkanes on the1D and2D dimensions, respectively. Hence, the1D peak capacity is1nc~700, and the2D peak capacity can in principle be2nc~20. Thus the ideal 2D peak capacity could in principle approach nc,2D~14,000 using the 120min1D run time. The limit of detection (LOD) for docosane, a representative analyte, was determined to be 1.5ppm injected concentration when 2µl of liquid sample was injected with a 20:1 split. A separation of diesel fuel demonstrated the practical utility of the instrument with this complex sample using a relatively fast run time of 20min and a short modulation period PMof 1s. Average peak widths-at-base of 5.4s and 166ms were achieved on the1D and2D dimensions, respectively. This yielded a1nc~220 and a2nc~ 6. Therefore, the 2D peak capacity is nc,2D~1320 with the 20min diesel separation.
authors: Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA.
authors: Chris E
authors: CE
authors: Freye
authors: Department of Chemistry, University of Washington, Box 351700, Seattle, WA, 98195-1700, USA. Electronic address: synovec@chem.washington.edu.
authors: Robert E
authors: RE
authors: Synovec
keywords: Comprehensive; Diaphragm valve; Gas chromatography; High temperature; Time-of-flight mass spectrometry; Two-dimensional