Preparation and Certification of River Sediment Reference Material for Polycyclic Aromatic Hydrocarbons

Matrix-type certified reference materials (CRMs) prepared from real environmental samples are used to ensure the reliability of environmental analyses and the comparability of results from different laboratories. Internationally, the National Institute of Standards and Technology (NIST) in the USA, the Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) in the European Union, and the UK Laboratory of the Government Chemist (LGC) have developed sediment CRMs for Polycyclic Aromatic Hydrocarbons (PAHs). Although some matrix-type CRMs are available for the quantification of PAHs in sediment and soils, their PAH contamination is mostly at the mg/kg level. Thus, they are not suitable for the QA of analyses of PAHs at the μg/kg level. In China, by restricting preparative techniques and value-assignment techniques of natural matrix CRMs, no CRMs of PAHs in sediment have been developed. Therefore, based on the foreign research experience, CRMs of PAHs in river sediment have been developed for Chinese environmental monitoring and scientific research. A method for developing CRMs of PAHs in sediment is described in this paper. Sediment sample was collected from Songhua River, and air-dried, ground, homogenized and sterilized. A good homogeneity was obtained by the testing for 16 kinds of PAHs from 15 units selected by a random stratified scheme covering the whole batch, and 3 sub-samples were analyzed in each unit. At 30℃ without direct sunlight, the concentrations of 16 PAHs were not changed during monitoring period of 16 months. Based on the results from difference analytical techniques including Gas Chromatography/Mass Spectrometry and Reversed-phase Liquid Chromatography by 11 collaborating laboratories, reference values for 14 PAHs are given, and reference values for 2 PAHs are in the range of 6.9-158 μg/kg. Expanded uncertainty of each PAH is 1.5-25 μg/kg. Since the values of PAHs in the CRM are much lower than those in other CRMs and are comparable to the actual PAHs content in sediment or soil, the CRMs are suitable for PAH monitoring in sediment and soil samples and method validation.