Time-Programmed Mass Spectrometry

A 90°-sector mass spectrometer (Hitachi Perkin-Elmer Model RMU-6E) has been modified for continuous repeated scanning of the mass spectrum in up to seven separate steps of different duration. The detector sensitivity settings and scanning rates can be selected individually for each step so that precise scans of mass peaks in different parts of the spectrum can be obtained repetitively and with minimum supervision. The peak heights can be conveniently referenced to the mass peaks arising from suitable standard peaks, and a variety of kinetic measurements can thus be performed using this device. The programmer described here is very inexpensive, compared to certain other data acquisition systems, and it is probably useful in many other instrumental applications as well.