Detailed simulation of mass spectra for quadrupole mass spectrometer systems

A method of computation to determine the trajectories of large numbers of i ons in quadrupole mass spectrometers has been developed. The computer progr am produces simulated mass scans with over 10(5) ions injected into the qua drupole model at each point on the mass scale. The computation method has b een combined with an improved representation of an ion source to predict th e behavior of complete quadrupole systems; the results obtained are shown t o reproduce most features of experimentally observed mass scans. The calcul ations show that the shape and height of mass peaks depend strongly on the properties of the ion source. However, ion source properties have a relativ ely small effect on the resolution of the mass spectrometer and an alternat ive to the common method of presenting the resolution of a quadrupole is pr oposed. This alternative better indicates the performance of the instrument as it is less sensitive to effects of the ion source. Results are also pre sented which indicate that peak splitting, closely matching experimental ob servations, can be produced by small changes in the exit aperture of the qu adrupole. (C) 2000 American Vacuum Society. [S0734-2101(00)00801-0].