Untitled

Abstract

An in-house reference material for trace metals in rice flour was produced. Certification of concentrations of fifteen elements based on at least two independent methods was carried out. The analytical techniques included ICP-AES, ICP-MS, ETAAS, FAAS and voltammetry. Out of the 15 elements, 13 elements, namely Na, K, Mg, Ca, Ba, Cu, Zn, Fe Mn, Co, Ni, Pb and Cd, could be certified whereas only reference values were given to Cr and V because the concentrations of these two elements were so low that only one analysis method could successfully detect them. Statistical tests for the study of homogeneity at 95 % confidence level did not reveal significant differences between the within-bottle and between-bottle variation. The rice flour material is considered to be homogeneous at 250-650 mg sample sizes. No significant change was observed in a long-term stability study of the material over a period of 5 months and a short-term stability study at an elevated temperature of 50 °C for a period of 5 weeks. A comparison of results obtained from independent methods was made before certified values were calculated using both means and weighted means. The reference materials have been distributed for use in laboratory quality assurance.