Prediction of quadrupole mass filter performance for hyperbolic and circular cross section electrodes

A computer model has been developed that is able to predict the performance of a quadrupole mass spectrometer (QMS) for any constant cross section electrode geometry. It has been used to predict the performance of QMS systems with both hyperbolic and circular cross section electrodes. The predictions confirm the limited previous work that indicates QMS performance is poorer when circular cross section electrodes are used rather than hyperbolic ones. There is also an indication that use of circular electrodes causes a movement of the peak position from the expected one and produces an extended tail on the low mass side of the peak.