Homogeneity study of candidate reference material (contaminated soil) based on determination of selected metals, PCBs and PAHs

Reference materials (RMs) are an indispensable part of QA/QC system and have played a critical role in the continual expansion of analytical capabilities of the analytical laboratories. The homogeneity study of the candidate for reference material is essential for the quality of reference material (certified reference material) used in quality assurance activities. The homogeneity study of candidate for reference materials of contaminated soil collected from a plot situated near the chemical factory "Rokita" in Brzeg Dolny (Silesian Region of Poland) for total metal content of Mg, Fe, Zn, Hg and analytes from a group of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) was carried out. The experimental design and study by using one way ANOVA showed no significant difference within and between bottle homogeneity and the material was found homogeneous. Total expanded uncertainty (k = 2) due to heterogeneity for all four metals and analytes from a group of PCBs and PAHs was determined within the range of 5-15%. The candidate for reference material of fortified soil was found to be homogeneous up to the minimum sample size of 100 mg for total Hg, 500 mg for Mg, Fe, Zn and 1 g from a group of PCBs and PAHs, and thus is suitable for certification.