An intercalibration exercise for trace metals in marine sediments

• Published in: Marine chemistry 1988-05, Vol.24 (1), p.13-28
• Main Authors: Loring, D.H, Rantala, R.T.T
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; Soil and rock geochemistry
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/0304-4203(88)90003-5

This paper describes the results of a recent ICES (International Council for the Exploration of the Sea) intercalibration exercise. (1/TM/MS) designed to compare various dissolution/extraction procedures used in the determination of major and trace metals in marine sediments and to examine and improve the reliability and comparability of such metal analyses within ICES member countries. Forty participants determined some, or all, of the Al, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Ti and Zn concentrations in replicate digests of three sediment samples using HF + aqua regia, aqua regia, 1 M HCl and 25% v/v acetic acid (HOAc) dissolution/extraction procedures and a separate procedure for Hg. HF+aqua regia dissolution proved to be the most effective method for removing the total trace metal concentrations from the samples, and 25% v/v HOAc was shown to be a weaker acid attack than 1 M HCl. Data analyses show that the intra-laboratory variations were acceptable for most replicate metal determinations except for Hg. The overall inter-laboratory agreements were, however, unacceptable for total Cd, Cr, Hg and Ni concentrations in all three samples. Acceptable agreements were obtained only for Al, Fe, Mn and Zn in all samples, Cu in only two samples and Pb in only one sample. Most inter-laboratory agreements were also unacceptable for most of the metals determined after dissolution/extraction by aqua regia, 1 M HCl, or 25% v/v HOAc. The use of inappropriate atomic absorption spectrophotometry procedures and the non-use, or misuse, of reference materials appear to be the main reasons for some poor individual laboratory performances and for the poor inter-laboratory comparability for many metals.