Report on the IUPAC/ISO REMCO/ BAM/EUROLAB-D Workshop on Proper Use of Environmental Matrix Reference Materials, Berlin, Germany, 22–23 April 1999

Report on the IUPAC/ISO REMCO/ BAM/EUROLAB-D Workshop on Proper Use of Environmental Matrix Reference Materials, Berlin, Germany, 22–23 April 1999

Dr. A. Fajgelj (Quality Assurance Supervisor, International Atomic Energy Agency Laboratories, A-2444 Seibersdorf, Austria; E-mail: A.Fajgelj@iaea.org), Chairman of the IUPAC Interdivisional Working Party on Harmonization of Quality Assurance Schemes for Analytical Laboratories, has submitted the following report:

IUPAC's Interdivisional Working Party on Harmonization of Quality Assurance Schemes for Analytical Laboratories, ISO's Committee on Reference Materials (ISO/REMCO), the German Federal Institute of Materials Research and Testing (BAM), and EUROLAB-D of Germany, have cooperated in organizing a workshop on "Proper Use of Environmental Matrix Reference Materials". The workshop was sponsored by the Institute for Reference Materials and Measurements (IRMM), European Commission, Belgium; the Laboratory of the Government Chemists (LGC), UK; and Promochem, Germany. It was supported by EURACHEM and hosted by BAM in Berlin, Germany on 22 and 23 April 1999.

In principle, the aim of the workshop was to increase awareness of how various types of reference materials (RMs) should be utilized. For this purpose, experts from different RM-producing organizations selected some of their existing RMs and focussed on the following topics: a) how the materials were characterized; b) how the materials were certified (absolute method, laboratory intercomparison, selected laboratories, certification criteria etc.); c) information about the assigned property values of traceability and uncertainty; and d) how the materials should be utilized properly by analysts in view of points a, b and c. Some lectures also included information about new strategies and plans in RM production. Information about ISO REMCO and COMAR (a reference materials database) was also given.

The following RM producers were represented at the workshop: Canada Center for Mineral and Energy Technology (CANMET)-Canadian Certified Reference Materials Project (CCRMP); Chinese National Research Center for Certified Reference Materials (GWB); Faculty of Agronomy and Institute of Chemical Technology, Czech Republic; Federal Institute of Materials Research and Testing (BAM), Germany; Laboratory of the Government Chemists (LGC), UK; Institute for Reference Materials and Measurements (IRMM), European Commission; International Atomic Energy Agency (IAEA); National Institute of Materials and

Chemical Research (NIMC), Japan; National Institute of Standards and Technology (NIST), United States; National Office of Measures (OMH), Hungary; and National Metrological Institute (NMI), Netherlands. In addition, some posters were presented and an exhibition of RMs was organized during the workshop.

From the general discussion, the following points can be summarized:

• Matrix reference materials are a specific type of reference materials. Within matrix reference materials, sub-groups also exist, i.e., gaseous RMs, environmental and biological matrix RMs, alloys, coal RMs, etc. To a large extent, differences in types of RMs are reflected in possible methods of characterization and certification of RMs and, consequently, in utilization of RMs in the analytical process.

• A large majority of matrix RMs is characterized through interlaboratory comparisons. Such materials do not always fulfill the criteria for the established traceability of the assigned property values. Most often, the uncertainty associated with the assigned property values is not quantified as required by the ISO Guide on Expression of Uncertainty in Measurement (GUM), Geneva, 1993.

• There is an urgent need for an up-to-date guidance on certification principles that would cover the above points (traceability and uncertainty). The new version of ISO Guide 35, Certification of Reference Materials: General and Statistical Principles, which is currently under revision by ISO/REMCO, will close this gap. Its first draft is expected to be available next year.

• Matrix RMs are frequently prepared for different purposes, i.e., calibration (gaseous RMs, stable isotope ratio RMs, alloys, etc.). The majority of matrix RMs available currently and in the future is and will be suitable for method validation, quality assurance, and quality control purposes, but not for calibration. Thus, the intended use of matrix RMs needs to be specified clearly by the producer.

• The instructions on proper use of reference materials given in ISO Guide 33 are of a general nature, because they are intended to cover all types of certified reference materials. Because ISO Guide 33, Uses of Certified Reference Materials, is also not in accordance with the GUM, it urgently needs to be revised. Additional guidance has to be prepared by the producers for each RM separately to reflect the intended use of the RM.

• It is the responsibility of an RM user to obtain the necessary information on the quality of an RM before selecting and using it for a specific purpose in the laboratory.

According to responses to a questionnaire distributed during the workshop, urgent and future needs for the following types of RMs were identified:

The workshop was attended by more than 100 participants from 34 countries. Full text of the lectures given by 17 presenters can be found in a special series proceedings book entitled The Use of Matrix Reference Materials in Environmental Analytical Processes(ISBN 0 85404 739 5) published by The Royal Society of Chemistry (see previous announcement in Chemistry International, 1999, Vol. 21, No. 3, p. 87).