title: Method to determine the true modulation ratio for comprehensive two-dimensional gas chromatography.
abstract: A new method is presented to determine the true modulation ratio, MR, from the measurable effective modulation ratio, MR*, in comprehensive two-dimensional gas chromatography, GC×GC, without the requirement for a detector at the end of the primary column. The method was developed through the investigation of modulator induced band broadening, as a function of1Wband the selected modulation period, PM, for simulated GC×GC data, by first defining primary column1D peak(s) and simulating the modulation process. Gaussian curve fitting is used to model each modulated secondary column separation peaklet,2D, in the unfolded GC×GC data to accurately determine the maxima of the peaklet distribution, followed by Gaussian curve fitting to the maxima to determine the effective1D peak profile and width,1Wb*. The relationship between1Wband1Wb* is studied as a function of the effective modulation ratio, MR*, which is1Wb* divided by PM, in order to determine the true modulation ratio, MR, which is1Wbdivided by PM. We explore how peak sampling phase (in-phase and out-of-phase) plays a role in the relationship between MRand MR*. Experimental validation of the simulated results is also provided, to span a range of commonly implemented conditions with typical1Wb(2-4.5s) and PM(0.25-8s). Use of MR<2 significantly broadens the1D peak (MR*≥1.2MR) corresponding to a loss in1D peak capacity,1nc≥20%. The new method relies upon mapping from MR* to MR, which is discussed in relation to peak capacity theories for GC×GC. It is found that optimizing1ncin GC×GC requires that1Wbis minimized and must be sampled with a sufficiently short PM(1-2s) to minimize modulator induced band broadening and a subsequent reduction in the effective1D peak capacity.
authors.affiliation: Department of Chemistry, Box 351700, University of Washington, Seattle, WA, 98195, USA.
authors.forename: David K
authors.initials: DK
authors.lastname: Pinkerton
authors.affiliation: Department of Chemistry, Box 351700, University of Washington, Seattle, WA, 98195, USA.
authors.forename: Brendon A
authors.initials: BA
authors.lastname: Parsons
authors.affiliation: Department of Chemistry, Box 351700, University of Washington, Seattle, WA, 98195, USA. Electronic address: synovec@chem.washington.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Synovec
mesh_terms: D002849:Chromatography, Gas / Q000379:methods*; D008956:Models, Chemical
keywords: Effective peak width; GC×GC; Modulation ratio; Peak capacity; Undersampling