English Abstract At the end of 1991 the interface part of the VG Plasma
Quad 2 plus ICP-MS was modified. This report describes the performance and
the level of molecular interferences of the modified ICP-MS apparatus. The
apparatus was optimized for maximal sensitivity, maximal stability and
minimal contribution of molucular interferences. Detection limits were four
to ten times better than with the standard ICP-MS apparatus and ranged from
6 ng/l for Cd to 1,3 mug/l for B. Using indium as an internal standard, the
short term stability was <2% RSD and the long term stability was <4% RSD for
elements in the mass range m/z = 51-208. Li, Be, B, Bi and Th had higher
RSD values due to unsuitability of the internal standard and to memory
effects. The precision ranged from 33% RSD at the detection limit to
0.2-0.7% RSD at 1000x higher concentrations (m/z=51-208). Calibration
curves were linear up to at least 200 mug/l. Spectral interferences due to
compounds of Na, Cl, S, Ca or Mg prevented the analysis of V, Cr, Ni, Cu,
Zn, As and Se at low concentration levels (<20 mug/l.)
