DECREASE OF SOLVENT WATER LOADING IN INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY BY USING A MEMBRANE SEPARATOR

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 degrees 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 x 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.