Application of a handheld X-ray fluorescence analyzer for the quantification of air particulate matter on Teflon filters

Abstract

Elemental characterization of air particulate matter samples through the application of X-ray fluorescence (XRF) spectrometry is a widespread analytical technique. This work presents the optimization and calibration methodology of a handheld XRF spectrometer and its subsequent application in elemental quantification of unknown particulate matter samples. The optimization of the handheld spectrometer was conducted through investigation of the elemental sensitivities and Limits of Detection (LoD) at variable excitation conditions (voltage, filter). Accordingly, five optimum operating conditions were obtained each one targeted in different elemental range: 1) Z = 11–12, 2) 12 < Z < 17, 3) 16 < Z < 23, 4) 22 < Z < 31 and 5) 30 < Z < 92. Subsequently, a number of reference (5 multi-element and 42 compound/single-element) materials were used to obtain calibration curves for 24 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Pb). Weighted least-square regression analysis was implemented to best fit the experimentally measured intensities with mass loadings resulting for most of the elements to high correlations (Pearson r > 0.98) and low statistical error. In addition, intercomparison of the elemental concentrations from 28 unknown particulate matter samples between the handheld and a benchtop XRF spectrometer showed good agreement.