Direct rapid quality assurance analysis of complex matrix materials: A chemometrics enabled energy dispersive X-ray fluorescence and scattering spectrometry application

Abstract

Compared to energy dispersive X-ray fluorescence (EDXRF) that is limited to analysis of elements (Z ≥ 13) via fluorescence and which is hardly direct, energy dispersive X-ray fluorescence and scattering (EDXRFS) spectrometry exploits additionally, scatter radiation to quantify both low- and heavy-Z elements as well as predict various material properties. The goal of this work was to demonstrate proof-of-concept for chemometrics-enabled EDXRFS spectrometry utilizing a weak sample excitation source towards rapid quality assurance (QA) analysis of complex matrix materials. A109Cd source was used to analyse three types of polymer powders - polypropylene (PP), low density polyethene (LDPE) and high density polyethene (HDPE) moulded as ∼ 2.5 g (∅ = 2.5 cm) pellets; and both actual as well as simulate lubricating oils spiked with trace additive metals B, Na, Ca, Mg, Fe and Zn and subjected to thermal degradation between 100 °C and 400 °C for 24 h. EDXRFS combined with principal components analysis (PCA) and soft independent modelling of class analogy (SIMCA) accurately identified polypropylene as well as differentiated it from both low density polyethene (LDPE) and high density polyethene (HDPE). LDPE and HDPE were fairly discriminated on the basis of density. In the second application partial least squares (PLS) modelling successfully determined the viscosity of lubricating oils utilizing the combination of the scatter peak and the Zn fluorescence signature, as well as correlated the lubricating oils viscosity to their thermal degradation. The reported method is applicable in industrial quality assurance due to its non-destructivity and speed.