Mass spectral interferences in the determination of trace levels of precious metals in human blood using quadrupole magnetic sector field and inductively coupled plasma mass spectrometry

The results of the determination of physiological levels of precious metals in blood with a new type of magnetic sector field high resolution (HR)-ICP-MS instrument are presented. Palladium levels, for example, ranged between 32 and 102.5 ng l(-1), HR-ICP-MS operating in the low resolution mode is advantageous for such ultratrace analyses as it is about 100 times more sensitive than in the HR mode or conventional quadrupole (Q)-ICP-MS. It is also shown that the determination of Rh and Pd in the ng l(-1) range is impaired by spectral interferences originating from Cd+, Pb2+, SrO+, RbO+ CuAr+ and ZnAr+. Using standard instrumental operating conditions on a Q-ICP-MS instrument, Pb2+:Pb+ and SrO+:Sr+ ratios were found to be about 0.1%, which results in a severe impairment of the determination of physiological Rh and Pd concentrations in body fluids. The resolution of the HR instrument used (m/Delta m = 7500) was not sufficient to separate Rh and Pd from all spectral overlaps. These remaining spectral interferences can only be overcome by an appropriate sample preparation step.