Aerosol particle size effects on plasma spectrometric analysis
A low-flow cascade impactor was used to evaluate the effects of tertiary aerosol particle size on inductively coupled plasma atomic emission spectrometry (ICP-AES) measurements. The impactor was used either on-line as a size-selective filter during measurements, or off-line for the determination of tertiary analyte mass particle size distributions. A pneumatic nebuliser and various thermospray sample introduction systems were studied. Particle size had little effect on background noise, although a 20% drop at small cut-off diameters was observed for the thermospray and improvements in signal to background noise ratios were observed using a 6-µm cut-off. Particle size also had little effect on measurement precision, however, it was important in determining how much signal was produced per unit mass of analyte transported. Analyte residing in aerosol particles of ⩽2.5 µm was shown to be much more efficiently utilised for signal production than that in larger droplets.