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A simple and inexpensive modification of a finnigan 3300 quadrupole mass spectrometer for negative ion detection
Author(s) -
Bruins A. P.
Publication year - 1983
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200100109
Subject(s) - dynode , electron multiplier , ion , quadrupole mass analyzer , mass spectrometry , quadrupole , multiplier (economics) , analytical chemistry (journal) , chemistry , atomic physics , physics , optics , chromatography , detector , photomultiplier , organic chemistry , economics , macroeconomics
The incorporation of a conversion dynode, positioned in the available space between the ion exit hole of the quadrupole and the entrance of the electron multiplier permits the detection of negative ions when this dynode is held at a high positive potential (4 kV). The system makes use of the original electron multiplier and does not require additional electrical feedthroughs into the vacuum system. The conversion dynode is also used for positive ion detection. It is then kept at −4 kV and helps to increase the gain for high mass ions, to reduce mass discrimination and to improve the signal to noise ratio.