The efficacy of neutron activation analysis for homogeneity testing of CRMs candidates of soil matrices

Abstract

ABSTRACT Certified reference materials (CRMs) are the cornerstone of the quality of analytical measurements. Homogeneity is a critical process in CRMs development. This study reports the use of instrumental neutron activation analysis (INAA) for the assessment of between-bottle homogeneity of four CRMs candidates of soil matrices, namely, soil from an agricultural area, soil from an industrial area, urban street dust, and surface marine sediment. The study also reports informative findings on the precision of INAA, besides uncertainty and detection limits (DLs). Eleven elements including nine toxic heavy metals (Cr, Fe, Mn, Co, Ni, Cu, Zn, As, and Cd) and two reference elements (Al and Si) were examined. Reference elements are used for the assessment of source contribution, i.e. crustal and anthropogenic, of elements. The uncertainty values of Al, Cr, Fe, Mn, Co, and As were < 5%, suggesting excellent accuracy of the INAA procedure, while the uncertainty ranges of Si and Zn contents were 10–40% and 1–16%, suggesting less accuracy than other examined elements. The uncertainty of Cd and Ni contents was not reported as they were below the DLs. Co recorded the lowest DL (0.15–0.27 µg/g) followed by As (0.27–0.56 µg/g), Mn (0.68–1.26 µg/g), and Cr (0.88–1.67 µg/g). The homogeneity was assessed based on the relative standard deviation (RSD) of seven bottles out of seventy bottles produced for a feasibility study purpose. For the CRM candidate of soil from an agricultural area, five elements (Cr, Mn, Fe, Co, and Zn), out of eight elements, recorded RSD less than 5%, indicating good homogeneity. For the CRM candidate of soil from an industrial area, seven elements recorded RSD% less than 2%, indicating excellent homogeneity. For the dust CRM candidate, six elements recorded RSD < 2%, indicating excellent homogeneity as well. Good homogeneity of the sediment CRM candidate was also obtained since six elements recorded RSD < 5%.