Simultaneous ultratrace determination of Zr and Nb in chromium matrixes with ICP-dynamic reaction cell MS

A dynamic reaction cell (DRC) has been used to minimize the formation of me tal-argide ions in inductively coupled plasma mass spectrometry and applied to the determination of Zr and Nb in Cr-rich samples. The formation of ArC r+ species from the plasma gas and the sample matrix was reduced by ion mol ecule reactions inside a DRC of the ICPMS used. Hydrogen was used as reacti on gas, and the efficiency in the reduction of ArCr+ was similar to that of other plasma-based polyatomic ions as reported in an earlier study. The fo rmation of CrOx+ ions is enhanced when the DRC is operated in pressurized m ode. Adjustment of the transmission properties of the band-pass quadrupole to reject precursor ions can be achieved without dramatic decrease of sensi tivity but with a significant improvement in the signal/background ratio. M easurements in solutions containing concentrations of up to 2 g/L Cr showed that the determination of Nb and Zr is possible in the nanogram per liter range in such a matrix. The limits of detection for Nb and Zr in pure Cr me tal have been estimated at 2 ng/g for Nb and 5 ng/g for Zr. Analysis of bas altic reference samples resulted in very good agreement with previously pub lished data.