کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5135752 | 1493450 | 2016 | 10 صفحه PDF | دانلود رایگان |
- Modulation induced band broadening for GCÂ ÃÂ GC is studied.
- True modulation ratio is determined from the measurable effective modulation ratio.
- Effective primary separation peak widths are measured with Gaussian curve fitting.
- Modulation induced loss of primary separation peak capacity is calculated.
- Modulation periods of â¼1 to 2Â s minimize broadening of primary separation peaks.
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 Ã 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 of 1Wb and the selected modulation period, PM, for simulated GC Ã GC data, by first defining primary column 1D 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 Ã GC data to accurately determine the maxima of the peaklet distribution, followed by Gaussian curve fitting to the maxima to determine the effective 1D peak profile and width, 1Wb*. The relationship between 1Wb and 1Wb* is studied as a function of the effective modulation ratio, MR*, which is 1Wb* divided by PM, in order to determine the true modulation ratio, MR, which is 1Wb divided by PM. We explore how peak sampling phase (in-phase and out-of-phase) plays a role in the relationship between MR and MR*. Experimental validation of the simulated results is also provided, to span a range of commonly implemented conditions with typical 1Wb (2-4.5 s) and PM (0.25-8 s). Use of MR < 2 significantly broadens the 1D peak (MR* â¥Â 1.2 MR) corresponding to a loss in 1D peak capacity, 1nc â¥Â 20%. The new method relies upon mapping from MR* to MR, which is discussed in relation to peak capacity theories for GC Ã GC. It is found that optimizing 1nc in GC Ã GC requires that 1Wb is minimized and must be sampled with a sufficiently short PM (1-2 s) to minimize modulator induced band broadening and a subsequent reduction in the effective 1D peak capacity.
Journal: Journal of Chromatography A - Volume 1476, 9 December 2016, Pages 114-123