ED-XRF set-up for size-segregated aerosol samples analysis

The knowledge of size-segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi-stage cascade impactors. In this work, samples were collected using a low-pressure 12-stage Small Deposit Impactor and a 13-stage rotating Micro Orifice Uniform Deposit Impactor™. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set-up for X-ray analysis. This work aims at setting up an energy dispersive X-ray fluorescence (ED-XRF) spectrometer to analyse quantitatively size-segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED-XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle-induced X-ray emission (PIXE), which is more frequently applied to size-segregated samples characterised by small PM quantities. A very good agreement between ED-XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter-comparability proves that our methodology is reliable for analysing size-segregated samples by ED-XRF technique. The advantage of this approach is that ED-XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi-stage impactors.