World‐wide intercomparison runs has made possible the certification of two new Polish geological‐environmental reference materials for multi‐element trace analysis: Apatite Concentrate (CTA‐AC‐1) and Fine Fly Ash (CTA‐FFA‐1). “Recommended values’ are established for 25 (CTA‐AC‐1) and 40 (CTA‐FFA‐1) elements respectively. In addition, “information values’ are assigned for 12 elements in CTA‐AC‐1 and 10 elements in CTA‐FFA‐1. Our method of data evaluation has been further improved and a modified version of criteria for assigning recommended and information values is proposed.
About 60 kg of fine fly ash was collected from the third zone of electrofilters from the "Kozienice" power station. The material has a density of 2.53 gþcm-3 at a very fine mesh size (93% passed through the 0.06 mm sieve). The material was rotated for 16 h in
a 110 L polyethylene (PE) drum placed in a specially constructed mixing device. Preliminary homogeneity checking was done by taking the samples from the drum at certain time intervals and analyzing them by XRF for their Y and Fe contents. After apportioning the material into PE containers, final
homogeneity checking was performed by instrumental neutron activation analysis. Determination of Fe, Co, Cr, Cs, Sc, and Th in subsamples from six containers chosen at random, with analogous results for subsamples taken from a single container, revealed that the material can be considered
homogeneous, at least for a sample size greater than or equal to 200 mg. An international intercomparison brought together nearly 60 laboratories from 19 countries employing a variety of analytical techniques as: neutron activation analysis (NAA), atomic absorption spectrometry (AAS), atomic
emission spectrometry (AES), X-ray fluorescence (XRF), mass spectrometry (MS), and others, with or without sample pretreatment and preconcentration or separation procedures. In total, about 3900 pieces of chemical data (over 950 laboratory means) on 65 elements were provided by participating
laboratories. Evaluation of results was done by the method previously proposed by one of us with some recent refinements. The procedure included the calculation of laboratory means, the use of four concurrent tests for outlier rejection (Dixon's, Grubbs's coefficient of skewness and coefficient of
kurtosis), calculation of the overall mean and its confidence interval etc. Using a set of appropriate criteria formulated earlier with some recent modifications it was found that it will be possible to certify at least 30 elements and provide "information values" for at least a further ten.
Observations on the performance of various analytical techniques and their contribution to the certification process are also presented.
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