Choosing a matrix effects correction method to quantify Cu, Zn, As and Pb in industrially contaminated soils by wavelength dispersive X-ray fluorescence spectrometry

Abstract

When quantifying the toxic elements Cu, Zn, As and Pb with X-ray fluorescence analysis in the soils contaminated by arsenic-containing industrial waste, there was a need to find some suitable methods for correcting of matrix effects caused by significant variations in the concentrations of the determined and interfering elements. The authors applied the XRF methods for calculating the elemental contents: external standard, Compton scattering correction, and α-correction with variable influence coefficients. The XRF results were validated with the atomic absorption spectrometry, the inductively coupled plasma mass spectrometry and the total reflection X-ray fluorescence spectrometry. This study showed that the Compton scattering correction is suitable for calculating the low-level contents of Cu, Zn, As and Pb in the contaminated soils, when the chemical compositions of soils are close to those of the calibration CRMs. If the contents of the determined and interfering elements in the contaminated soils varied significantly none of the above XRF methods provides the correct XRF results. The errors characterizing the difference between results of XRF and comparison methods (RSD) reached 20–90% rel. To compensate significant inter-element influences in such soils, the authors proposed the equation containing the Compton scattering component and empirical α_ij- influence coefficients. As a result, the RSD values were significantly reduced, amounting to: Cu 1.1–7, Zn 3–12, As 1.6–9 and Pb 2–9.5% rel. The maximum contents of target elements in highly contaminated soils were as follows, μg/g: Cu 6036, Zn 13,550, As 10,880 and Pb 4976. Thus, the combined correction approach ensured the WDXRF determination of the high contents of target elements in the studied soils.