STUDIES ON SPECTROSCOPIC AND NONSPECTROSCOPIC INTERFERENCES IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

In the present thesis, the mechanisms of spectroscopic interference (s pectral overlap caused by interfering ion species) and non-spectroscop ic interference (matrix effect) in inductively coupled plasma-mass spe ctrometry (ICP-MS) were clarified, and analytical methods to reduce su ch interference described. Interfering ion species were classified int o two group: refractory oxide (MO+) and Ar polyatomic ions (ArX+ X =: H,C,O,N). The MO+ resulted from the ionization of undissociated neutra l oxides in the ICP. A higher plasma temperature and/or the lower part ial pressure of oxygen in the ICP would he required to reduce the form ation of oxide ion species. The formation of ArX+ was related to a col lision-induced reaction of Ar with X+ occurring at the interface regio n, and the use of shielded ICP suppressed the collision. While, in ICP -MS coupled with the electrothermal vaporization (ETV) technique, inde pendent matrix effects were observed. One was ''signal enhancement cau sed by hydrogen mixed with argon carrier gas''; the other was ''signal enhancement caused by a halogen matrix''. Both signal-enhancement eff ects resulted from the promotion of ionization of analytes through a c harge-transfer reaction and/or electron impact. In order to reduce suc h matrix effects, the separation of trace elements from the matrix con stituents would be required.