Advances in Instrumentation and Data Analysis Techniques for Increasing Peak Capacity and Peak Capacity Production in One and Two-Dimensional Gas Chromatography
Fitz, Brian David
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Techniques to substantially increase peak capacity (number of peaks per separation window) and peak capacity production (number of peaks produced per unit time) for one and two-dimensional gas chromatography are demonstrated. First, instrumental advances related to sample introduction and column heating rate are discussed. Rapid sample introduction to the chromatographic system was achieved with a thermal injection device to deliver ultra-narrow peaks onto the GC column. When compared to standard sample introduction, thermal injection can provide peaks that are ~10 times narrower which gives rise to peak capacities an order of magnitude larger when compared to traditional GC practice. To further increase peak capacity and peak capacity production, a low thermal mass (LTM) GC system operated at a heating rate of 250 °C/min was applied with thermal injection to produce a separation with a peak capacity of ~300 in 1 minute. Additionally, thermal injection was applied to a comprehensive two-dimensional gas chromatographic system coupled to time-of-flight mass spectrometry (GC × GC – TOFMS) to produce a separation with a peak capacity of ~6,000 in 6 minutes, affording a peak capacity production rate of ~1,000 peaks/minute. Second, a novel algorithmic approach for processing GC-TOFMS data is presented which can increase the peak capacity and peak capacity production values even further. The algorithm relies on GC-TOFMS data that is sampled with sufficient data density (> 100 points/peak) to accurately measure analyte peak widths, W, and retention times, tR. Separation visualization is made possible by transforming the data from a signal versus time format to a peak width versus retention time format. This is achieved by measuring the W and tR of each m/z for each analyte in the separation, followed by plotting of the data (W vs. tR) in a two-dimensional format. Plotting the data in this fashion allows for the visualization of pure and interfered m/z of analytes. Coupled with chemometric analysis allows for the deconvolution of poorly-resolved analytes down to a resolution, Rs = 0.03. The peak capacity of a 7 minute GC-TOFMS separation was increased from ~400 to ~10,000 using this technique.
- Chemistry