Comprehensive Three-Dimensional Gas Chromatography with Time-of-Flight Mass Spectrometry

Development of comprehensive, three-dimensional (3D) gas chromatography with time-of-flight mass spectrometric detection (GC³/TOFMS) is described. This instrument provides four dimensions (4D) of chemical selectivity and includes significant improvements to total selectivity (mass spectrometric and chromatographic), peak identification, and operational temperature range relative to previous models of the GC³ reported. The new instrumental design and data output are evaluated and illustrated via two samples, a 115-component test mixture and a diesel fuel spiked with several compounds, for the purpose of illustrating the chemical selectivity benefits of this instrumental platform. Useful approaches to visualize the 4D data are presented. The GC³/TOFMS instrument experimentally achieved total peak capacity, n_c,3D, ranging from 5000 to 9600 (x̅ = 7000, s = 1700) for 10 representative analytes for 50 min separations with component dimensional peak capacities averaging 406, 3.6, and 4.9 for ¹D, ²D, and ³D, respectively. Particularly, GC³/TOFMS achieved a combined ²D × ³D peak capacity ranging from 10 to 26 (x̅ = 17.6, s = 5.0), which is similar to what is achieved by ²D alone in a GC × GC operating at equivalent modulation period conditions. The analytical benefits of employing three varied chemical selectivities in the 3D separation coupled with TOFMS are illustrated through the separation and detection of 1,6-dichlorohexane and cyclohexyl isothiocyanate as part of the diesel fuel analysis.