| Abstract: | Identification and detection limits for scanning and non-scanning mass spectrometers are discussed. It is theoretically deduced and experimentally confirmed that these limits are on the low pico-and femtogram levels, respectively, when using conventional secondary electron multiplier-amplifier systems. The sensitivity can be increased at least tenfold by pulse-counting techniques, instead of current amplification, provided the chemical noise is sufficiently low. The potential advantages of a detection system for simultaneous ion detection in a significant mass range, for obtaining complete mass spectra in fast GC/MS analyses, are demonstrated. A double focusing mass spectrometer was constructed, using the well-proven Mattauch-Herzog principles. By application of an “electronic photoplate”, substance identification in the low femtogram range on a millisecond time scale, so far only accessible for single ion monitoring techniques, is feasible. |
