Abstract

Three reference materials for As, Cd, Co, Cu, Hg, Ni, Pb and Sb – 8 inorganic elements in leather powder were developed with relatively low, middle and high concentrations. The reference materials were prepared by adding an appropriate concentration using industrial process. The concentration range of the three levels is within the ± 200% of the limited value in the China statute Safety Technical Specifications for Childrenʼs Footwear (GB 30585-2014).1 By using 16 units with duplicate analysis, it was shown that the samples were enough to demonstrate the homogeneity of these candidate reference materials. The statistical results from the stability test, also showed no significant trends in both short-term stability test for one week at 40°C and long-term stability test for 23 months. This set of reference materials, were used for more than two certification methods – including isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS), inductively coupled plasma mass spectroscopy (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The combined relatively standard uncertainties of the reference values were estimated by considering the uncertainties of the analytical methods, homogeneity and stability. The range of the expanded uncertainties of all the elements is from 3% to 5%. The certified reference materials (CRMs) are primarily intended for use in the calibration and validation of procedures for the determination of inorganic elements in in leather or similar leather samples.