Feasibility studies on the suppression of HfO+ mass interferences on platinum determination by inductively coupled plasma mass spectrometry (ICP-MS) by modification of the sample introduction system

A novel approach for the elimination of isobaric interferences in quadrupole-ICP-MS is described. In this work the removal of HfO+, the main interference, from platinum determination using a new method is proposed. Selective retention of hafnium on activated silica capillaries during the sample introduction step with a direct injection nebulizer (DIN) has been obtained. The influence of the activation of the fused silica surface of the sample capillary of the DIN has been investigated. While the hafnium has shown an interaction with the negatively charged surface, resulting in retention inside the capillary, the interaction with platinum was negligible. The retained hafnium could be removed after platinum detection by flushing the capillary with 2.5 mu L of 1.7 mol L-1 hydrochloric acid several times. The effects of the flow rate and the acid concentration of the sample on the elution step for removal of the interferences and capillary regeneration have been investigated. The analytical performance of this method has been demonstrated by comparative calibrations of platinum in the presence and absence of a highly concentrated Hf matrix. The method has been successfully applied to the determination of platinum in car exhaust fumes.