Direct Determination of Dissolved Silicon in Atmospheric Precipitation by CH.sub.4-Ar Mixed Plasma DRC-ICP-MS

Author(s): Jiangyi Zhang [sup.1] [sup.2] , Zhifang Xu [sup.1] [sup.2] Author Affiliations: (1) grid.458476.c, 0000 0004 0605 1722, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, [...]
Direct determination of dissolved silicon (DSi) in atmospheric precipitation by ICP-MS is still a challenge because of the presence of serious mass interferences. In this work, a reliable method based on CH.sub.4-Ar mixed gas plasma DRC-ICP-MS was successfully used for the direct determination of DSi in atmospheric precipitation samples. The interfering ions (.sup.14N.sup.14N.sup.+, .sup.12C.sup.16O.sup.+) were directly removed by the reaction with carbon dioxide gas and could be reduced by up to 99% at m/z 28. In addition, the sensitivity of .sup.28Si.sup.+ was 2-fold improved by CH.sub.4 modifier that was introduced to the ICP plasma at 2 mL/min, and the background signal was decreased to 60%. Under the optimized conditions, the limit of quantification was 5 [mu]g/L, and the reproducibility (RSD) was generally less than 3%. The proposed method was assessed using surface water standard reference materials, and the measured values agreed well with the certified values.