Optimization of experimental conditions of thin-window EPMA for light-element analysis of individual environmental particles

Different metallic substrates such as beryllium, aluminium, silicon and sil ver were rigorously tested in all aspects of energy-dispersive electron pro be x-ray microanalysis of single particles, including the semi-quantitative determination of low-Z elements. The effect of the collecting substrate on the capability to locate, to analyse and to classify particles automatical ly was extensively studied by the analysis of particulate standards and aer osol particles collected at the Belgian coast. Beam-sensitive particles suc h as ammonium sulphate and ammonium nitrate were analysed using a liquid ni trogen-cooled sample stage. The dependence of the beam-damage effect on the type of collecting substrate was also studied using standard aerosol parti cles. The results obtained show that the use of beryllium as a collecting s urface offers some advantages: (i) detailed spectral information can be obt ained in a broad elemental range (6 less than or equal to Z less than or eq ual to 92) without overlap with x-ray lines of the substrate and (ii) compl ete chemical classification can be done with one set of analyses. Copyright (C) 2001 John Wiley & Sons, Ltd.