Certified Reference Materials for Research in Antarctica: The Case of Marine Sediment

Abstract

A multielemental certified reference material based on Antarctic marine sediment was prepared in the framework of the Italian Programma Nazionale per la Ricerca in Antartide (PNRA, National Program for Research in Antarctica) and was coordinated by the Istituto Superiore di Sanità (ISS, National Institute of Health). The sediment was collected during the 9th Italian Expedition (1993–1994) in Antarctica in Terra Nova Bay (Ross Sea) at a depth of 80 m, stored at −20°C in polyethylene containers, and shipped to the ISS. The sediment was subjected to preliminary treatment at the Institute for Reference Materials and Measurements (IRMM, Joint Research Centre of the European Commission, Geel Establishment, Geel, Belgium). This treatment consisted of sieving, drying, jet milling, sampling, moisture determination, particle size determination, and microscopic examination. The final product turned out to contain mostly particles smaller than 90 μm (97% of total mass); particles larger than 150 μm were practically absent. The fraction between 90 and 150 μm comprised mainly organic material homogeneously distributed over the sediment. Five hundred two brown glass bottles (polyethylene insert and plastic screw cap; capacity 120 ml) could be thus filled with this material, each bottle containing about 75 g of the sediment. The certification project was accomplished with the active participation of eight internationally reputed laboratories from various countries (Belgium, Denmark, Hungary, Italy, Spain, and United States). The instrumental techniques resorted to in the certification exercise included cold vapor atomic absorption spectrometry, electrothermal atomization atomic absorption spectrometry, flame atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, isotope dilution inductively coupled plasma mass spectrometry, isotope dilution mass spectrometry, neutron activation analysis, solid sampling Zeeman electrothermal atomization atomic absorption spectrometry, and Zeeman electrothermal atomization atomic absorption spectrometry. The certified values established for some trace elements are as follows: Al, 67.1 ± 3.3 mg/g; As, 4.41 ± 1.06 μg/g; Cd, 0.538 ± 0.027 μg/g; Cr, 42.1 ± 3.4 μg/g; Co, 6.87 ± 0.31 μg/g; Fe, 24.4 ± 0.7 mg/g; Mn, 446 ± 19 μg/g; Ni, 9.56 ± 1.05 μg/g; Pb, 21.0 ± 2.9 μg/g; Zn, 53.3 ± 2.7 μg/g. In turn, additional elements were quantified by some participants. Homogeneity of the powdered sediment for the various analytes is such that intakes as low as 100 mg still show no deviation from the nominal values larger than the attached uncertainty. Intakes of 200 mg are, however, recommended to minimize any possible variations in concentration. The product has an average moisture content of 0.30 ± 0.03% on delivery.