Removal of spectral interferences and accuracy monitoring of trace cadmium in feeds by dynamic reaction cell inductively coupled plasma mass spectrometry

In the direct ICP-MS determination of Cd in feed samples, significant spectral interferences caused by high concentrations of Mo can play an important role. In the present study, Mo based oxide or hydroxide polyatomic interferences were eliminated by dynamic reaction cell (DRC) with O2 as reaction gas. Some other oxide or hydroxide interferences (i.e. Zr and Ru) were simultaneously reduced by this technology. These potentially interfering polyatomic ions 95Mo16O+, 94Mo16OH+, 94Zr16OH+, 98Mo16O+, 98Ru16O+ and 97Mo16OH+ on 111Cd+ and 114Cd+ were oxidized to higher oxides MoO2+, MoO3+, MoO4+, RuO3+, RuO4+, MoO2H+, MoO3H+, ZrO2H+ and ZrO3H+. The rejection parameter q (RPq) of DRC and the flow rate of O2 were optimized and set at 0.75 and 2.0 ml min− 1, respectively. In addition, the residual isobaric interference of 114Sn on 114Cd was corrected using a mathematical correction equation. The limit of quantitation (LOQ) for 111Cd or 114Cd was 0.8 or 1.0 ng g− 1 and the analysis results of NIST 1567a wheat flour and 1568a rice flour standard reference materials were in good agreement with the certified values. As the routine cadmium monitoring method in our laboratory, the proposed method was applied to the accuracy determination of 562 pig feed samples for the Monitoring of Central Meat Reserves (CMR) of China.