Decrease of solvent water loading in inductively coupled plasma mass spectrometry by using a membrane separator

Abstract

A hollow-fibre polyimide membrane separator was used to decrease the water loading on an inductively coupled plasma (ICP). An aerosol generated by a pneumatic nebulizer, after large droplets had been removed in a spray chamber, was passed through the membrane separator heated at 80 °C. Water in the aerosol was evaporated and removed as water vapour from the inside to the outside of the hollow fibres, and consequently only a dry aerosol was introduced into the ICP. The levels of polyatomic ions, such as ArO⁺ and ClO⁺, decreased by one and two orders of magnitude, respectively. The CeO⁺ : Ce⁺ ratio, cerium being one of the strongest oxide-forming elements, could be decreased to 1.1 × 10^–3 under conditions such that the maximum count rate of Ce⁺ was obtained. The Ba²⁺ : Ba⁺ ratio obtained with the membrane separator was relatively lower than that obtained with a cooled spray chamber. Ion kinetic energies were also lowered with decreasing water loading.