The effect of plasma reactions on arsenic measurement by ICP spectrometry.

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.