Automated analysis of submicron particles by computer‐controlled scanning electron microscopy

Abstract

Summary: Automated analysis of submicron particles by computer-controlled scanning electron microscopy is generally possible. The minimum diameter of the detectable particles is dependent on the mean atomic number of the particles and the operating parameters of the scanning microscope. The main limitation with regard to particle size is set by the quality of the particle detection system, which generally is the backscatter electron detector. The accuracy of the results of the x-ray analyses is very often strongly affected by specimen damage, omnipresent especially for environmental particles even at low electron energies and probe currents. With the exception for light elements, the detection limit is approximately 1 wt%. Device-related limitations to automated analysis may be specimen drift and an unreliable autofocus function.

A method for sizing submicrometer particles in air collected on Formvar films and imaged by scanning electron microscope

“…Particle size and morphological parameters can be a resolved down to 2-5 nm diameters while chemical elements can be mapped down to 50-100 nm diameters, but at a higher accelerating voltage. Microscopic methods, however, are tedious and time consuming and great progress has been made to develop automated scanning methods in the submicron size range (Poelt et al, 2002;Ocker et al, 1995). But these automated methods require a highly plain substrate and sufficiently good contrast between the aerosol particles and their background (Poelt et al, 2002).…”

“…Microscopic methods, however, are tedious and time consuming and great progress has been made to develop automated scanning methods in the submicron size range (Poelt et al, 2002;Ocker et al, 1995). But these automated methods require a highly plain substrate and sufficiently good contrast between the aerosol particles and their background (Poelt et al, 2002). To ensure that the collected ambient aerosol particles are imaged over all size ranges, without any disturbances by stigmatism or defocusing, the aerosol samples must be scanned manually.…”

Chemical Composition of Aerosols and Its Relation to the Gas-Phase Precursors in Mexico City During the 2003 Cold Dry Season

“…Therefore, to achieve semi-quantitative analysis on micro particles is usually not straightforward. Numerous previous works intended to do that by several methods including no correction, that is to say simply normalised relative net intensities (Laskin & Cowin, 2001), correction of matrix effects by the so-called ZAF correction without any correction for the geometric effects (Poelt et al, 2002), correction for matrix and geometry for ideally-shaped particles (Armstrong & Buseck, 1985) by a reverse Monte Carlo quantification program (Ro et al, 2003). Using these different quantification methods, this study aims at defining the most appropriate substrate for automated single particle analysis.…”

Evaluation of quantitative procedures for X‐ray microanalysis of environmental particles

“…Among the possible microanalytical techniques, scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDX) is a powerful technique allowing individual particle imaging and elemental analysis (Fletcher et al, 2001). Moreover, single-particle analysis can be performed on a representative number of particles in a fully automated way by using image analysis and stage control (Mulders and Endert, 1992;Poelt et al, 2002;Watt, 1990). Besides, atmospheric thin-window X-ray detectors offer extended capabilities for low-Z element analysis.…”