Determination of organochlorine compounds, petroleum hydrocarbons, and sterols in a sediment sample, IAEA-383. Results of an intercomparison exercise

A worldwide interlaboratory analytical comparison exercise was organised us ing a lagoon sediment as sample material (IAEA-383). A total of 54 laborato ries from 41 countries reported results for organochlorine pesticides, PCB congeners, aliphatic and aromatic petroleum hydrocarbons, and sterols. The statistical treatment of the data indicates that the accurate determination of these organic contaminants in sediments is still a delicate task for en vironmental laboratories and, for many compounds, the relative standard dev iations of the mean concentration values are relatively large. The difficul ties with analytical accuracy and precision are nearly the same in several regional programmes and they do not seem geographically biased. Thus, furth er progress is needed and may be achieved with analytical training and rein forced participation of the laboratories in proficiency testing schemes. Ne vertheless, the statistical treatment of the data reported by the laborator ies participating in this exercise allowed the assignment of reference valu es for many analytes. Based on the experience of previous exercises, the as signed reference values are likely a very good estimate of the true concent rations of analytes, although the confidence limits of those Values are rel atively broad. This sediment sample can now be used as a Reference Material in Quality Control and assist laboratories with assigning concentration va lues in environmental samples of similar matrix. In particular for sterols this is the first sediment material available with information on analyte c oncentrations.