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Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.5, #8)
Legislative limits below detection capability1 by S. L. R. Ellison; V. J. Barwick; A. Williams (pp. 308-313).
A study of contaminant emission data collected for paper and pulp mills in the United Kingdom over a 1-year period is presented. For most sites and analytes, the data could not demonstrate positive compliance with absolute emission limits to water in the 1 g range in large (million tonne) effluent streams, even though some sites were apparently removing contaminants from their water supply. The implications are discussed, with particular reference to the implications of results quoted at 'detection limits' or 'reporting limits'.
Keywords: Key words Detection limit; Compliance; Regulation; Paper and pulp mills
Producing SI-traceable reference values for Cd, Cr and Pb amount contents in polyethylene samples from the Polymer Elemental Reference Material (PERM) project using isotope dilution mass spectrometry by J. Vogl; D. Liesegang; M. Ostermann; J. Diemer; M. Berglund; C. R. Quétel; P. D. P. Taylor; K. G. Heumann (pp. 314-324).
The present paper describes the certification of the amount content of Cd, Cr and Pb in two different polyethylene materials within the third phase of the Polyethylene Elemental Reference Material (PERM) project. The analytical procedure to establish the reference values for Cd, Cr and Pb amount contents in these materials is based on isotope dilution mass spectrometry used as a primary method of measurement. Cd and Pb were measured with inductively coupled plasma-mass spectrometry and Cr with positive thermal ionization-mass spectrometry. The decomposition of the polymer matrix was carried out using a high pressure asher. Reference values for amount content, traceable to the SI-system, have been obtained for these three elements in both of the polyethylene samples of PERM. For each of the certified amount content values an uncertainty budget was calculated using the method of propagation of uncertainties according to ISO and EURACHEM guidelines. The measurement procedures, as well as the uncertainty calculations, are described for all three elements. In order to keep the whole certification process as transparent as possible, the preparations of various reagents and materials as well as the sample treatment and blending are described in detail. The mass spectrometry measurements and the data treatment are also explained carefully. The various sources of uncertainty present in the procedure are displayed in the uncertainty budgets. The obtained combined uncertainties for the amount content values were less than 2% relative (k=1) for all investigated elements. The amount contents were in the μmol/kg range, corresponding to mg/kg levels.
Keywords: Key words PERM; ICP-MS; PTI-MS; IDMS; Uncertainty budget; Certification; Polyethylene
Assessment of the ICP-MS method using the interlaboratory QA study of two Polish soil RMs by V. Balaram (pp. 325-330).
Under an international collaborative certification programme, two new Polish soil reference materials, PL-1 (loess) and BPGM-1 (sandy loam soil), were analysed for 34 trace elements including all the rare earth elements using the acid decomposition method and inductively coupled plasma - mass spectrometry (ICP-MS). After the certification by the organisers, the analytical data obtained at our institute were compared with the certified data. 'Z-score' values calculated for individual trace elements helped in the assessment of the quality of the data. While the majority of the data obtained on ICP-MS was very precise and accurate, some of the data especially for elements such as Zr, Hf and Nb suffered from incomplete dissolution of the sample and spectroscopic interferences. For some trace elements, certified data are not available for comparison. These features together with the usefulness of interlaboratory collaborative programmes and ICP-MS for the certification of soil reference materials are discussed.
Keywords: Key words ICP-MS; Collaborative certification programme; Polish soil reference materials; Z-score; Acid dissolution; Trace elements
Establishment of SI-traceable reference ranges for the content of various elements in the IMEP-9 water sample by I. Papadakis; P. D. P. Taylor (pp. 331-338).
The International Measurement Evaluation Programme (IMEP) attempts to shed light on the current state of the practice in chemical measurements. The main tool, which assists this attempt and also differentiates IMEP from similar projects, is the establishment of SI-traceable reference ranges (where possible) for the elements offered for measurement to the participants for every IMEP round. The Institute for Reference Materials and Measurements (IRMM), as the founder and co-ordinator of IMEP has the responsibility of establishing the SI-traceable reference ranges. This is a large task that requires knowledge, skill and resources. IRMM collaborates with a network of reference laboratories in order to achieve the establishment of SI-traceable reference ranges in a transparent and reliable way. The IMEP reference laboratories must have demonstrated experience and have a proven and successful record in the use of primary methods of measurements (mainly isotope dilution mass spectrometry) and the application of uncertainty evaluation according to ISO/BIPM guidelines. In IMEP-9 "trace elements in water", results from 7 reference laboratories (including IRMM) were combined by IRMM to establish SI-traceable ranges for the 15 elements, which were then offered for measurement to the 200 participants worldwide. This paper does not discuss the individual contribution of the reference laboratories (this could be the subject of individual papers) but describes the procedures and criteria used in order to establish the reference ranges for the IMEP-9 samples by combining the individual contributions. All results submitted to IRMM are included, so as to make this publication as realistic as possible.
Keywords: Key words IMEP; Certification; Uncertainty calculation; Metals in water; Interlaboratory comparison
The role of certified reference materials in ensuring the quality of spectrochemical measurements – the present status in Romania by S. Duta (pp. 339-345).
The objective of quality assurance programme for spectrochemical measurements is to reduce the measurement errors to accepted limits. Reference materials are being widely used as measurement standards in the fields of industrial production, environmental protection and clinical chemistry, and are playing an important role in ensuring the quality of measurement results. This paper presents some aspects, practices and examples of the activity of the Reference Materials Laboratory of the National Institute of Metrology, Bucharest, in the field of spectrochemical measurements. An attempt to describe the role and use of reliable certified reference materials to ensure the quality of spectrochemical measurements is presented. A short review of the locally available certified reference materials used in spectrochemical measurements is given. The use of reference materials data in estimating the measurement uncertainty is discussed. An interlaboratory comparison, recently organized in Romania, is also presented as a useful response to the need for quality assurance of spectrochemical results.
Keywords: Key words Reference materials; Quality assurance; Spectrometric system; Measurement uncertainty
Uncertainties in qualitative testing and analysis by S. L. R. Ellison (pp. 346-348).
Members of the working group at the time of publication are as follows: A Williams (Chairman), S Ellison (Secretary), M Berglund, W Haesselbarth, K Hedegaard, R Kaarls, M Mansson, M Rosslein, R Stephany, A van der Veen, W Wegscheider, H van de Wiel, R Wood. The group includes representatives from other bodies as follows: CITAC: Pan Xiu Rong, M Salit, A Squirrell, K Yasuda., AOAC International: R Johnson, Jung-Keun Lee, D Mowrey. IAEA: P De Regge, A Fajgelj. EA: D Galsworthy. It is presented with a view to developing policy and promoting work on the topic. Comments on the content and the issues raised are invited, and should be addressed to the working group secretary (above).
The status of traceability in chemical measurements – A EURACHEM Workshop
by J. Garaj (pp. 349-351).