Analytical Sciences

The Effect of Plasma Reactions on Arsenic Measurement by ICP Spectrometry

Koichi CHIBA and Tomohiro NARUKAWA

National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan

Inductively coupled plasma mass spectrometry (ICP-MS) is of great value to researchers concerned with inorganic analytical chemistry as well as to engineers performing elemental analysis. However, the effects of the plasma reactions on ICP spectrometry are still incompletely understood and they sometimes introduce severe problems for measurements, such as spectral interferences. When we determine arsenic (As) by ICP-MS or ICP-AES, we observe two interesting plasma phenomena; one is the incoherent molecular formation (IMF) effect in the plasma, and the other the selective and partial oxygenation of ions with O₂ gas in a dynamic reaction cell. The mechanisms of the IMF effect and selective oxygenation of As with a reaction gas were investigated and the techniques to remove their influence on As determination are discussed.

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