Indicative properties measurements by SEM, SEM-EDX and XRD for initial homogeneity tests of new certified reference materials

Abstract

This manuscript reports, for the first time, the use of SEM, EDX and XRD for initial homogeneity test of seven new environmental certified reference materials (CRMs), which are under development at our laboratories. The proposed CRMs, which will be certified for essential and toxic elements, are soil, dust, sediment, leaves, dates and fish. Between-bottles homogeneity test was carried out in terms of indicative properties of CRMs rather than the certified properties. SEM was used to test particle-size distribution. The major particle-size of CRMs of soil, dust, sediment, leaves and fish are 20–60, <20–60, 40–80, 50–100 and 70–100 μm, respectively. The ranges of the mean, standard deviation (SD) and mean deviation (MD) were 0.29–70.3%, 0.09–1.48 and 0.08–1.21, respectively. EDX was used to quantify the percentages of major elements (Si, O, N, S, Ca, Al, K, Fe, Mg, Zn and Cu). The percentage ranges of the mean, SD and MD for all elements were 1.57–48.15%, 0.11–5.84 and 0.09–4.4, respectively. XRD was used to quantify the percentages of the major minerals. The ranges of the mean, SD and MD were 1.57–48.15%, 0.11–5.84 and 0.09–4.40. All SD and MD values showed low level of dispersion indicating satisfactory homogeneity. Additionally, the relative standard deviation values of all dominant indicative properties did not exceed 10% confirming satisfactory homogeneity. SEM, EDX and XRD offered useful, rapid and simple measurements for initial homogeneity test of the CRMs.