REDUCTION OF SOME SELECTED SPECTRAL INTERFERENCES IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

The reduction of spectral interferences has been investigated and both aerosol desolvation and the utilization of high mass resolution have been applied in order to improve detection limits for V, Cr, Ga, Ge and As, which are subject to interferences by polyatomic ions in solutions containing Cl. Experiments with a laboratory-made quadrupole ICP-MS have been performed in order to optimize the desolvation parameters. Ion signals corresponding to ClO+ and ClOH+ are reduced by more than one order of magnitude if appropriate heating and cooling temperatures are chosen. A reduction in polyatomic ions like ClO2+, Cl2+ and ArCl+ by using desolvation was also observed. With the prototype of a new double-focusing ICP-MS system from Finnigan MAT, Bremen, Germany, operated in the low resolution mode, the detection limits with desolvation have been determined and were found to be up to 2 orders of magnitude lower compared with measurements without desolvation. The detection limit (3s) for V in 0.4 mol l-1 HCl was reduced from 25 to 1 ng ml-1. High mass resolution improved the detection limits for V, Cr and Ga in HCl by up to 4 orders of magnitude compared with measurements in the low resolution mode (2 pg ml-1 for V in 0.4 mol 1(-1) HCl), and lowest detection limits have been obtained with the combination of desolvation and high mass resolution (0.6 pg ml-1 for V in 0.4 mol l-1 HCl).