Limitations on analysis of small particles with an electron probe: Pollution studies

Recent literature concerning the size and composition of airborne lead particles in automobile exhaust emission determined by electron microprobe analysis reports fourteen distinct lead compounds. Particle sizes reported were from 0·2 μm to 2 μm in diameter. The determination of chemical formulae for compounds requires quantitative elemental data for individual particles. It was also assumed that the lead-bearing particles analysed were solid (specifically non-porous or non-fluffy) compounds which occurred as discrete (non-aggregate) particles. Intensity data obtained in our laboratory from the excited volume in a 1 μm-diameter sphere of solid lead chloride indicate insufficient precision and sensitivity to obtain chemical formulae as reported in the literature for exhaust emission products.