A simple and precise method for direct determination of molar ratio of 206Pb/ 204Pb, 207Pb/ 204Pb and 208Pb/ 204Pb by ICP-MS was developed. The data acquirement parameters of MS for Quadrupole setting time(QST), Dwell time(DT), Integrated time and number of sweeps were investigated in detail. The relative standard deviation(RSD) of different Pb isotope ratios were less than 0.32%[n=5, ρ(Pb)=20 ng/mL]. The mass discrimination and dead time of detector was calibrated by using NIST981 solution. The mass bias factor(α) of 206Pb/ 204Pb, 207Pb/ 204Pb and 208Pb/ 204Pb were 0 002 5, 0 002 9 and 0 002 0, respectively. The dead time of detector was 7 ns. The proposed method has been applied to the analysis of geological standard reference materials containing AGV-1, BCR-2 and BHVO-2 .The relative error between this work and the recommend values or reported values was better than 0.73% and the relative standard deviation was better than 0.93%(n=5).
The influence of different concentrations of acetic acid matrix on elemental ICP-MS signal was investigated.The analyte signal intensities were suppressed with higher concentration of acetic acid.However,signal enhancements occur under certain conditions.The matrix inducedchanges are highly dependent on the nebulizer gas flow rate and power.Higher concentration of acetic acid is thought to contribute to local cooling in the central channel of the plasma.As the concentration of acetic acid increases from 2% to 5%,analyte signal intensities decrease and oxide ratio increase,especial in the high nebulizer gas flow rate.Higher incident power and low nebulizer gas flow rate can allow the plasma to accept a change in the concentration(2% to 5%)of acetic acid without significant change analyte signal.
