Abstract
Four proficiency tests of environmentally significant elements in soil and water are described. The effects of sample matrix, analyte, sample preparation procedure, extraction method efficiency and instrumental technique on laboratory performance were assessed. Participants’ performance was evaluated using z scores and E n scores. One study included dried sediment and sediment digest as test samples. By testing both dried sediment and sediment digest in the same study, differences in laboratories’ results due to the extraction method or instrumental technique were evaluated. Cadmium and nickel were the elements with the most unsatisfactory z scores for dried sediment compared to sediment digest. The second study had as test samples river water and river water fortified with biosolid. For an evaluation of the efficiency of participants’ extraction method, the results reported for the analysis of river water were compared to the results for analysis of the same river water fortified with biosolid. No consensus could be found between participants’ results for Cr and Ni in this study as the extraction method employed by them produced results that were too variable. The last two studies included saline and fresh water samples. The analysis of fresh and saline water samples with similar analyte concentrations assisted laboratories in developing their methods for trace elements in saline water. For Cr, Pb and Se, the assigned values were reference values traceable to SI, measured using isotope dilution inductively coupled plasma mass spectrometry. Saline water containing low concentrations of analytes presented difficulties to some laboratories. Arsenic and selenium were the analytes most difficult to analyse in all types of environmental samples.
References
Australian and New Zealand Environmental Conservation Council (2000) ANZECC water quality guidelines for fresh and marine waters, October 2000
ILAC-G13:2007, Guidelines for the requirements for the competence of providers of proficiency testing schemes
Thompson M, Ellison SLR, Wood R (2006) The international harmonized protocol for proficiency testing of (chemical) analytical laboratories. Pure Appl Chem 78:145–196
ISO 13528:2005 Statistical methods for use in proficiency testing by interlaboratory comparisons
Thompson M (2000) Recent trends in inter-laboratory precision at ppb and sub-ppb concentrations in relation to fitness for purpose criteria in proficiency testing. Analyst 125, 385–386
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Antin, L., Armishaw, P. Aspects of proficiency testing studies of trace elements in environmental samples with a focus on laboratory performance. Accred Qual Assur 15, 467–471 (2010). https://doi.org/10.1007/s00769-010-0672-y
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DOI: https://doi.org/10.1007/s00769-010-0672-y