Direct determination of trace cadmium in environmental samples by dynamic reaction cell inductively coupled plasma mass spectrometry

Cadmium is subject to significant Zr and Mo based oxide/hydroxide interferences in ICP-MS analysis of environmental samples. In this work, a dynamic reaction cell (DRC) technology was used to eliminate these metal oxide/hydroxide interferences. The potentially interfering ions (94)Zr(16)OH(+), (94)Mo(16)OH(+) and (95)Mo(16)O(+) on (111)Cd(+) were oxidized to higher oxides (94)ZrO(2)H(+)/(94)ZrO(3)H(+), (94)MoO(2)H(+)/(94)MoO(3)H(+), and (95)MoO(2)(+)/(95)MoO(3)(+) by O(2) as the reaction gas in DRC. Under the optimized O(2) flow rate (2.0 mLmin(-1)) and DRC rejection parameter q (Rpq, 0.75), the background signal was reduced by up to 100-fold at m/z 111 and the limit of quantitation (LOQ, 10σ) of 0.1 ngg(-1) was obtained. The proposed method was applied to direct analysis of trace Cd in a series of soil and sediment standard reference materials and the satisfactory results showed that it has great potential for the direct determination of trace or ultra-trace levels of cadmium in environmental samples.