ICP-MS has been used for determination of metallic impurities in pure water used in semiconductor industry and showed excellent detection capabilities for most metallic elements in the periodic table. However, some elements still have difficulty to analyze lower than 1 pg/ml (ppt) due to higher background on ICP-MS instrument. There are two sources of background: isobaric or polyatomic ion interferences due to plasma Ar and sample matrices, and contamination from sample introduction devices. Several techniques have been used for elimination of the isobaric and polyatomic ion interferences. High resolution ICP-MS can separate analytes from interferences, but some elements require extremely higher resolution, which sacrifices sensitivity of analytes. The cool plasma technique can eliminate interferences that have higher ionization potential, but elements having higher ionization potential or strong bond energy with oxygen cannot be analyzed. The dynamic reaction cell (DRC) technology can effectively reduce the interferences that the cool plasma technique cannot reduce by chemical resolution. In addition, non-extraction lens design allows very low level of B determination. In this paper, several introduction devices and operating conditions with the DRC-ICP-MS were evaluated to reduce background. The results of Si and B in pure waters clearly showed the difference between the multiple water collection sites at less than ng/ml (ppb) level.
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