Renaissance of gas chromatography-time-of-flight mass spectrometry. Meeting the challenge of capillary columns with a beam deflection instrument and time array detection

This report describes the use of a unique beam deflection time-of-flight mass spectrometer to address some of the demands made on mass spectrometry by new developments in high-resolution capillary column gas chromatography. An integrating transient recorder is used in combination with this beam deflection time-of-flight instrument to apply the concept of time array detection in capturing all of the mass spectral information available from the ion source, thereby greatly enhancing the signal-to-noise ratio quality of the mass spectral data. The applicability of the time array detection approach to gas chromatography-mass spectrometry is demonstrated in the context of an analysis of the standard Grob mixture for assessing performance of capillary column chromatography. During analysis of the Grob mixture by gas chromatography-mass spectrometry, mass spectra were recorded at a rate of 20 scan files per second. The data indicate that this rate of mass spectral scan file generation is adequate to provide a suitable data base for reconstruction of the chromatographic profile. In addition, the effective scan rate is high enough that there is no distortion in the relative peak intensities throughout the individual mass spectra of components regardless of the relatively high dynamic changes in partial pressure of the analyte as reflected by the sharp peaks in the chromatographic profile. The experimental results indicate that the beam deflection time-of-flight mass spectrometer can provide mass spectra at a scan file generation rate much higher than that possible with the conventional quadrupole or magnetic sector mass spectrometer, but at comparable detection limits.