Radiant energy – Ionic separation or analysis – Cyclically varying ion selecting field means
Patent
1984-02-23
1985-08-13
Smith, Alfred E.
Radiant energy
Ionic separation or analysis
Cyclically varying ion selecting field means
250282, H01J 4942
Patent
active
045352364
ABSTRACT:
This invention relates to a method of operating quadrupole mass spectrometers with only an RF potential applied to the filter rods so that the spectrometer operates to pass all ions above a particular value of m/e. In practice, spectrometers operated in this way usually show a marked loss in transmission efficiency for ions of high m/e when operated with an RF potential low enough to pass ions of m/e<10, and the invention overcomes this defect by providing a method of switching the RF potential between two or more values at which ions of different ranges of m/e values are efficiently transmitted, and combining the output signals at each value to give a resultant signal more accurately proportional to the number of ions formed in the source of the spectrometer, irrespective of their m/e values. The invention can be used to improve the accuracy of total pressure measurement using a conventional residual gas analyzing mass spectrometer, eliminating the need for additional pressure gauges.
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Donald J. Jenden et al., "A Multiple Specific Ion Detector and Analog Data Processor for a Gas Chromatograph/Quadrupole Mass Spectrometer System", J. Chrom. Sci., 1973, II, pp. 601-606.
Berman Jack I.
Smith Alfred E.
VG Instruments Group Limited
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