Comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry detection with a 50 ms modulation period

Abstract

An ultrafast flow modulation period, PM of 50 ms, for comprehensive two-dimensional (2D) gas chromatography (GC × GC) with time-of-flight mass spectrometry (TOFMS) detection is demonstrated, producing narrow peak widths, 2W (4σ width-at-base on the 2D dimension), demonstrating the potential for ultrafast (2D) separations with high peak capacity. The modulator is a pulse flow valve that injects a narrow pulse of carrier gas at a user defined PM, at the union between the 1D and 2D columns. The raw data produced combines the properties of vacancy chromatography and frontal analysis. Deconvolution of the raw data using unconstrained multivariate curve resolution alternating least squares (MCR-ALS) analysis facilitates identification and quantification for overlapped analyte peaks. The peak profile loadings obtained from MCR-ALS are converted into traditional appearing GC × GC data through a process commonly used with frontal analysis. An 18-component test mixture at seven different injected mass levels was studied. The 2D peaks generated ranged from an 2W of 16 to 36 ms with an average of 26 ms. At an on-column injected mass of 14 ng per analyte, an average mass spectral match value, MV, of 822 was achieved using in-house collected spectra for comparison, with an average match value RSD of 7.1%. Calibration of overlapped test analytes was evaluated using the areas of the MCR-ALS loadings, with excellent quantification demonstrated. The advancement demonstrated in modulation performance for GC × GC represents a significant decrease in PM as most commercial modulators have a minimum PM of 1 s, while maintaining the benefits of a duty cycle of essentially 1.0, which promises to enable new chemical analyzer designs, compatible with the vacuum requirements of the TOFMS detector.