Cadmium suffers from significant Zr and Mo based oxide/hydroxide interferences during Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) analysis of environmental samples, which can result in a significant deviation of the results. Direct determination method of Cd in environmental geological samples by ICP-MS with membrane desolvation has been developed in this study. This method can effectively eliminate the interference of Zr, Mo oxides and hydroxides, and ensure the results are accurate and reliable. Compared with the conventional method of ICP-MS, the interference of Zr and Mo oxides and hydroxides can be reduced to 0.001% when membrane desolvation is used. Meanwhile, the sensitivity of Cd can be increased 3.5 times. Under the given conditions, the detection limit of Cd was 0.28 ng/L, the lower limit of determination was 2.2 ng/L, and the precision (RSD,
n=12) was 2.2%. The method was applied to analyze 20 Chinese environmental geological reference materials. The analytical results are consistent with the certificated values. It indicates that the proposed method has a great potential for the direct determination of trace or ultra-trace levels of cadmium in environmental geological samples. At the same time, the method was used to determine Cd in two comparison samples between two laboratories in 2016. This comparison was organized by the China National Nuclear Corporation. The
Z-scores were 0.500 and -0.964, respectively for the two laboratories, and the absolute values of
Z were less than 2.
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