INDUCTIVELY-COUPLED PLASMA OPTICAL-EMISSION SPECTROMETRY USING NEBULIZERS WITH WIDELY DIFFERENT SAMPLE CONSUMPTION RATES

A pneumatic, high-efficiency nebulizer (HEN), consuming only 50 mu L of sample per minute, produced detection limits for most lines that were within a factor of 3 of those exhibited by commonly used pneumatic nebulizers that use 1.0 mL of sample per minute. Detection limits were within a factor of 8 for all lines observed, despite the 20 times smaller sample consumption rate for the HEN compared to commonly used nebulizers. The aerosol properties were measured and related to the observed vertical emission profiles, Ar emission intensities, and ion to atom emission intensity ratios. The aerosol properties and plasma excitation conditions were used to understand the origins of the nebulizer-dependent sensitivities, background, and background fluctuations that control detection limits. More than 90% of the primary aerosol volume produced by the HEN had drop diameters less than 10 mu m. The analyte transport efficiency was 20% for the HEN compared to 1.5-2% far the commonly used nebulizers. More emission intensity was produced per microgram of analyte entering the plasma when the HEN was used in place of the other nebulizers.