Reduction of molecular ion interferences with hexapole collision cell in direct injection nebulization–inductively coupled plasma mass spectrometry

Abstract

A hexapole collision cell was investigated for significant reductions of interferences by molecular ions in inductively coupled plasma mass spectrometry (ICPMS) using a direct injection high efficiency nebulizer (DIHEN). Collision induced reactions with hydrogen reduced isobaric interferences while the addition of helium as a collision gas enhanced analyte ion transmission through collisional focusing. Improved figures of merit were obtained for elements (Ca, Fe, Cr, As, Se) that are typically difficult to analyze with conventional quadrupole instruments. Sensitivities achieved with the DIHEN were higher (by factors ranging from 2 to 9) than those observed with a micronebulizer-spray chamber arrangement. Precision and detection limits were similar to or slightly improved over values obtained using the micronebulizer-spray chamber arrangement. The technique was successfully applied to the determination of Fe, Cr, Co, Cu, Pb, Al, Mn, Zn, Ag, and Sr on silicon wafer surfaces at a concentration range of (0.49–6.5) × 10⁹ atoms cm⁻², sampled by a 100 µL drop of H₂O–H₂O₂–HF, as well as for the determination of Cr in DNA.