Effect of sample aerosol transport rate on inductively coupled plasma atomic emission and fluorescence

Abstract

Spatially dependent changes in the atomic emission and atomic fluorescence intensities in an argon inductively coupled plasma (ICP) as a function of the aerosol transport rate (mass of aqueous aerosol introduced per unit time) have been observed. The ion emission intensity per mass of analyte introduced into the plasma (responsivity) decreases as increasing amounts of aerosol enter the ICP. The decreasing ion emission responsivity was observed at all vertical and radial locations. Fluorescence responsivities either remain constant or increase as the sample aerosol transport rate is increased. Ion emission to fluorescence intensity ratios decrease with increasing aerosol transport rate. The decrease in ion emission responsivity is due mainly to changes in the fraction of ions that are excited and emit light, rather than to a decrease in the number of ions produced in the plasma. In contrast, both the magnitude and direction of changes in atomic emission and fluorescence responsivities with variations in aerosol loading are spatially dependent.