CALCULATION OF INTENSITIES OF MOLECULAR INTERFERENCES IN GD-MS - APPLICATION TO ANALYSIS OF ALUMINUM-ALLOYS

A method for calculating the concentration of molecular ions in GD-MS is reported. The method is based on measurements of effective stabilit y factors (ESF) of molecular ions. ESPs have been measured for various types of molecular ions: combination of Ar with gases and components of the sample; components with each other and gases. An investigation was carried out, by using a cryo-cooled pin-cell, on 5 aluminium stand ard materials. It is shown that ESFs for different types of molecular ions lie in the small range 1 x 10(-9)-10(-8) ppm(-1), except for ArH, hydrides, oxides and nitrides of metals. Comparison with reaction ra te constants show that polarization grip of an atom by an ion is mainl y responsible for more or less uniform values of ESFs. With use of thi s method a program for mathematical simulation of mass-spectra was dev eloped. The relative errors of calculated intensities of interferences do not exceed the 15% level. The method provides a way for more accur ate estimations of unresolved interferences and gives a comprehensive idea of the spectrum in a given region.