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 94Zr16OH+, 94Mo16OH+ and 95Mo16O+ on 111Cd+ were oxidized to higher oxides 94ZrO2H+/94ZrO3H+, 94MoO2H+/94MoO3H+, and 95MoO2+/95MoO3+ by O2 as the reaction gas in DRC. Under the optimized O2 flow rate (2.0 mL min−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 ng g−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.