Comparison of a priori and interlaboratory-measurement-consensus approaches for value assignment of multi-element reference materials on PTFE filters

Multi-element reference materials (ME-RM) were prepared with 28 elements on polytetrafluoroethylene (PTFE) filters utilizing a custom aerosol deposition system and certified multi-element solutions designed to mimic atmospheric particulate composition. ME-RM were then distributed to eight participating laboratories who provided measurement results via X-ray fluorescence (XRF), particle induced X-ray emission (PIXE), and inductively coupled plasma mass spectrometry (ICP-MS). Lab-consensus loadings computed following an international methodology agreed well with a priori ones for Na, Al, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, As, Se, Rb, Sr, Cd, and Pb. The lab results were in good agreement with a priori reference loadings for S, K, Ca, V, Mn, Fe, Co, As, Se, Rb, Sr, Cd, and Pb. This work demonstrates the ability of the custom aerosol chamber to generate consistent reference filters that can be used for instrument calibration and quality control, interlaboratory comparison, and proficiency testing purposes, filling a much-needed gap hitherto lacking because of unavailability of suitable reference materials.