IMPROVEMENTS IN OR RELATING TO GAS CHROMATOGRAPHY-MASS SPECTROMETRY

摘要

1,255,962. Mass spectrometers. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 16 June, 1969 [5 July, 1968], No. 32335/68. Heading H1D. In a combined gas chromatography-mass spectrometry system in which the output from a gas chromatographic column 1, comprising samples mixed with a carrier gas, is fed to the ion source 3, a transverse magnetic field, e.g. from permanent magnet 9, is applied to the ion beam from the ion source 3 to deflect the relatively light carrier gas ions in the beam and prevent them from impinging on a total ion beam monitor electrode 14, whilst leaving the relatively heavy sample ions substantially undeflected. The beam monitor electrode 14 precedes a mass analyser 6 and the magnet 9 is disposed between ion source 3 and the monitor electrode 14. As shown, the magnet 9, disposed adjacent beam-aligning electrodes 17, 18, is located between ion source 3 and an electrostatic analyser 5 which further separates the carrier gas beam 10 and the sample ion beam 11. An apertured electrode 13 intercepts the carrier gas beam 10 but passes sample beam 11 which is partly intercepted by beam monitor electrode 14 which detects the presence of a peak in the sample ions and initiates magnetic scans in the sector 6 to determine the mass spectra of successive corresponding samples from column 1. In an alternative embodiment, Fig. 2 (not shown), at least one pair of beam-aligning electrodes is disposed parallel to the ion beam and the magnetic field is applied before these electrodes so that the carrier gas beam is deflected outside the plates and does not enter the electrostatic sector 5. The magnetic field may also be formed by an electromagnet, and the carrier gas may be helium or hydrogen. The ion source 3 uses a 50 ev. electron beam to ionize the sample and carrier.