Assessment of sample preparation methods for the analysis of trace elements in airborne particulate matter

The determination of trace element composition of airborne particles usually requires dissolution in acidic media followed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. Analytical methods are usually validated on NIST SRM 1648 and 1648a, but without any further discussion regarding their application to real atmospheric samples. Here, we present an assessment of 5 digestion methods (over a hot plate and using a microwave system) for SRM 1648a and atmospheric particles based on the analysis of 30 elements by ICP-MS. Recoveries of NIST-certified elements for SRM 1648a confirm that a digestion method using HNO3-HF on a hot-plate yields acceptable recoveries for most of the NIST-certified elements (with the exception of Cr). By conducting the elemental analysis in triplicate samples of particles collected on PTFE filters, we determined that the analytical method is reproducible within 9% for real PM samples. Heterogeneity of the reference material and atmospheric samples, as well as differences in chemical composition and particle size between both, suggests that uncertainties related to the dissolution of trace elements using acidic mixtures are not well characterized.