Modification of an AEI/GEC MS9 High-Resolution Mass Spectrometer for Electron Impact/Chemical Ionization Studies

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Abstract
A double-focusing MS9 mass spectrometer has been modified to permit operation in both chemical ionization (CI) and electron impact (EI) modes. The modifications consist mainly of a closed ion chamber, a high capacity pumping system, a reactant gas inlet system, a new solid sample probe, and a source pressure measuring device. Changes have also been made in the electronic system and a new ion source power supply has been incorporated. The new ion source can be operated in the CI mode at pressures up to 1 Torr while the pressure in the analyzer is better than 10−7 Torr. The new set-up has the ability to analyze solid, liquid, and gas samples in both CI and EI mode. It has also the ability to do GC/MS without a Separator. The sensitivity in the CI mode is comparable to the sensitivity in the EI mode, and the maximum resolution obtained with the CI/EI source is similar to that obtained with the original EI source.