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

An ultrafast flow modulation period, P_M 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 P_M, 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 P_M as most commercial modulators have a minimum P_M 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.