Advances in Instrumentation and Data Analysis Techniques for Increasing Peak Capacity and Peak Capacity Production in One and Two-Dimensional Gas Chromatography

Abstract

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.