The effect of adventitious water in hexapole collision cell inductively coupled plasma mass spectrometry

This paper considers several aspects of the role of water in collision cell inductively coupled plasma mass spectrometry. Studies with water and deuterium oxide, employed both as samples and as impurities in the cell gas, were used to investigate the origins of the polyatomic ions. It was found that no new species were formed in the cell as water from the plasma provides the basic reactive components; however, some were greatly enhanced when the cell gas was deliberately wetted. The reactivity of the water/deuterium oxide dominated the cell chemistry when an unreactive gas such as He was used, indicating a need for careful control of water content, but the effects were greatly reduced when a reactive gas such as hydrogen was also employed. It is concluded that water could be a useful reagent molecule, if its partial pressure can be adequately controlled. Seeking complete removal of water from the reagent gas is unnecessary as there is a baseline contribution from the plasma and, in any case, when reactive reagent gases are used its effect is minimal.