Analytical Intercomparison Exercises and Harmonization within Environmental Laboratories from Developing Countries

Abstract

Since the early 60's, the IAEA implements a Quality Assurance (QA) programme for the Member States. As part of this programme, the IAEA organized more than 150 analytical intercomparison exercises and produced more than 70 Certified Reference Materials for a wide range of determinands, encompassing radionuclides, trace elements, petroleum hydrocarbons, pesticides and PCBs. From the IAEA — Marine Environment Laboratory in Monaco, analytical Quality Assurance services are provided for non-nuclear contaminants in marine materials.

Results of recently organized worldwide intercomparison exercises using the sample materials IAEA-142 (mussel tissue homogenate) and IAEA-140 (seaweed homogenate), show that some progress was achieved worldwide in the analyses of the more common environmental contaminants. However, results also show that difficulties in obtaining accurate data for trace elements and especially for organic contaminants are still widespread, particularly in developing countries. Therefore, the success of international cooperative programmes as well as of many regional environmental monitoring programmes, depends on improved quality and comparability of data which has to be achieved still through reinforced Quality Assurance programmes. To this aim, the IAEA/UNEP/IOC-UNESCO inter-agency programme on marine pollution promotes the adoption of Reference Methods for harmonization of techniques used in developing and developed countries, organizes frequent intercomparison exercises, and produces certified marine Reference Materials which are made available to laboratories worldwide.     

An overview of laboratory performance studies conducted by the IAEA for marine pollution studies of metals and organic contaminants

Aspects of the International Atomic Energy Agency (IAEA) Analytical Quality Control Services (AQCS) for marine environmental studies are discussed, focusing on recent laboratory performance studies (LPS) and the production of reference materials for trace metals and organic compounds in various marine matrices. The IAEA has organized seventeen global interlaboratory studies for a range of organic contaminants. Of note has been the inclusion of numerous polychlorinated biphenyl congeners (PCBs) and some sterols of anthropogenic origin. Concurrently, there have been eleven worldwide intercomparison exercises for trace metals in the marine environment, most of which included methylmercury. Although such interlaboratory studies can help improve performance in individual laboratories and regional laboratory networks, the results reveal that problems remain in the determination of some metals and many organic contaminants.     

IAEA reference materials for quality assurance of marine radioactivity measurements

The IAEA's Marine Environment Laboratory has been assisting laboratories in Analytical Quality Control Services (AQCS) for the analysis of radionuclides in the marine environment since the early seventies. AQCS through world-wide and regional intercomparison exercises and the provision of reference methods and reference materials (RM) have been recognized as an important component of quality assurance/quality control. A total of 43 intercomparison exercises were organized and 37 RM were produced for marine radioactivity studies. All important marine matrices were covered, e.g., seawater, marine sediments of different chemical compositions, fish, shellfish and seaplants. RM were prepared from samples collected at contaminated sites (e.g., the Irish Sea, the Baltic Sea, the Arabian Sea, Mururoa and Bikini Atolls, etc.) as well as from sites affected only by global fallout (e.g., the Pacific Ocean). Available RM are listed in the IAEA biennial catalogue and can be purchased at a minimal price. An overview of prepared RM for radionuclides in marine matrices is presented and discussed in more detail.     

Inter-laboratory comparisons: Determination of actinides in excreta

Inter-laboratory tests are a means of assessing the analytical coherence of medical laboratories. In radiotoxicology, this kind of exercise makes it possible to keep up with laboratory know-how and with the evolution and relative performances of analytical techniques (precision and reproducibility). However, the goal of the laboratories taking part in these annual exercises is not only to check the accuracy of their results. The analytical discussions and the chance to compare experiences enrich the group's general competence.French biologists have been organizing annual radiotoxicology intercomparison exercises since 1978. The exercises are carried out within the framework of a working group (GT1) operating under the aegis of the French Atomic Energy Commission's (CEA) Medical Coordinator. Using reports and diagrams which present the results obtained by the participants in the form of syntheses, the authors describe how the exercises for determining actinides in excreta (urine and faeces) are organized, how the results are evaluated in terms of the analytical methods used, and the improvements made in analytical and metrological performance.Up until 1985, these exercises were limited to French laboratories. Since then, the exercises have acquired an international dimension, opening up to include interested foreign radiochemists, initially from European laboratories, and now from laboratories worldwide. At the present time, 35 laboratories representing 9 countries take part regularly in these intercomparison exercises.     

Applied environmental metrology for studying health-pollution interactions

Nuclear and isotopic techniques are valuable tools in assessing the levels of environmental pollution by toxic elements and for studying how these contaminants affect human health. More than 90 counterparts from 55 countries around the world have participated in projects on these topics, supported by the International Atomic Energy Agency (IAEA), during last ten years. With the support of the IAEA, for example, an appropriate metrology for compositional characterization of size fractionated airborne particulate matter was developed, verified and implemented in more than 40 countries. This paper reviews the development and application of environmental metrology tools involving nuclear analytical and isotopic techniques, as seen from the particular perspective of IAEA programmes.     

Certifying the chemical composition of a biological material — a case study

A worldwide laboratory intercomparison was organized by the International Atomic Energy Agency's Analytical Quality Control Services (AQCS) involving the determination of trace elements in plant materials used for human consumption. The National Institute of Standard and Technology (NIST) Standard Reference Materials Program donated 5 kg of spinach designated for the production of the future Standard Reference Material SRM 1570a to this intercomparison; the AQCS provided a similar amount of cabbage. For the study, 150 units of each material were distributed and 114 laboratories reported results on both materials to AQCS. The results for the spinach, encompassing more than forty elements, have been compiled and evaluated; estimates of the elemental concentrations were made based on statistical evaluations, principles of analytical procedures and the laboratory performance indicated by the results on the cabbage material. Satisfactory estimates were obtained for 27 elements. Comparison with IAEA laboratory and NIST reference data did not reveal any significant bias that might have been introduced by the intercomparison approach or its evaluation.     

Certification of trace and major elements and methylmercury concentrations in a macroalgae (Fucus sp.) reference material, IAEA-140

A marine reference material, IAEA-140, prepared with a macroalgae (Fucus sp.) was recently produced by the International Atomic Energy Agency and certified for trace and major elements and for methylmercury (MeHg). Certification of this material was achieved as an outcome of an international analytical intercomparison study which resulted in 116 independent sets of results reported by participants from 54 countries. The statistical evaluation of the collected data and the criteria used for assignment of the mean and uncertainty values are described. The analysis of data allowed to certify concentration values for 24 elements and MeHg, and to provide information values for another 10 elements. Regarding the elements which could be given certified values, between two and eight different instrumental methods were used to measure metal concentrations, and four independent analytical procedures were used to measure MeHg concentrations. In order to assess the results of the certification procedure, a comparison was made between the certified values obtained from the world-wide intercomparison results and the values obtained from a small subgroup of well-qualified laboratories. The means and 95% confidence intervals for reference values obtained by the two methods are similar for most elements showing that the usual method of certification used by the IAEA, based on large groups of participants, is indeed pertinent.     

Problems of chromium analysis in biological materials: An international perspective with special reference to results for analytical quality control samples

Detailed results are presented in this paper for all analytical quality control samples distributed by the IAEA including a new animal muscle intercomparison material of very low chromium content, and an attempt is made to draw some conclusions regarding likely sources of analytical error.     

Investigation of air pollution in Chile using biomonitors

A project has been undertaken to carry out a long term study on atmospheric air pollution in Chile using biomonitors. Samples of different species of lichens were collected in clean areas (native forest), analyzed and transplanted to the Santiago Metropolitan Area. In addition, samples of Tillandsia recurvata were collected in the Metropolitan Area for comparison purposes. The preparation of the samples was done under controlled, cryogenic conditions and analyzed by neutron activation analysis and solid sampling atomic absorption spectrometry. As part of the routine QA/QC procedures, the analytical laboratories, have participated in intercomparison runs organized by the IAEA for the determination of trace and minor elements in two lichens samples. The present paper describes the activities carried out within the framework of this project. This revised version was published online in July 2006 with corrections to the Cover Date.     

International Atomic Energy Agency's contributions to advances in nutritional and environmental metrology

For more than three decades the International Atomic Energy Agency (IAEA) has supported projects on food, nutrition and environment for strengthening the analytical capabilities in developing countries (DCs). Over time, such efforts have led to the development of proper study designs, harmonization of sampling protocols, adequate contamination control and evaluation of the suitability of competing analytical techniques for the determination of specific analytes. Collectively, these consistent IAEA initiatives have promoted harmonization of chemical measurements thus facilitating comparability of results of filed investigations. Importantly, the Agency's efforts have infused a measure of metrological awareness in measurements carried out in field studies, including physiological measurements. Nuclear and isotopic techniques have played an important role in reaching these goals by establishing reliable measurement processes for application in health care studies.     

Environmental pollution study by multielemental neutron activation analysis of garden soil samples from Nagpur City, India

A multielemental instrumental neutron activation analysis (INAA) method has been employed for the determination of 30 elements in seven garden soil samples from Nagpur City and two intercomparison soil standards from IAEA, Vienna and Institute of Radioecology and Applied Nuclear Techniques (IRANT), Slovak Republic. Environmental implications of elemental concentrations in different soils have been discussed.     

The International Atomic Energy Agency's program on analytical quality control

For more than thirty years the International Atomic Energy Agency has been assisting laboratories in Member States in maintaining and improving the reliability, i.e. the quality of analyses of nuclear, industrial, environmental and biological materials, and materials of marine origin. Through the Analytical Quality Control Services (AQCS) the Agency initiates and supports improvements in the accuracy of analytical chemical and radiometric measurements and their traceability to basic standards. This is achieved by organizing worldwide and regional intercomparison exercises and by distributing reference materials. The latest biological and environmental reference and intercomparison materials are presented and general information is given on the preparation of materials, intercomparison runs, and the evaluation of reference data. Means to improve the quality of intercomparison results are presented and discussed.     

An intercomparison exercise on the determination of neptunium-237 in an environmental material

An intercomparison exercise has been carried out on the measurement of²³⁷Np in a sample of sea-born sediment taken from the estuary of the River Esk in Cumbria, United Kingdom. The sediment had been contaminated by radioactive liquid discharges from the nuclear fuels reprocessing plant at Sellafield. The measure of agreement between the submitted values was such that one would accept with confidence²³⁷Np analyses reported by the participating laboratories. The exercise was arranged by the Analysts' Informal Working Group (AIWG). The AIWG is a small group of chemists from several Government laboratories in the United Kingdom having an interest in radionuclides in the environment. From time-to-time the Group arranges intercomparison exercises; these exercises are in addition to the members' normal quality assurance schemes, and in addition to intercomparison exercises arranged by other organizations. So far as the authors are aware, there has been no report of such an exercise involving²³⁷Np, and there appear to be no natural matrix reference materials available for environmental²³⁷Np.     

Elemental characterisation through instrumental neutron activation

Neutron activation has been used to characterise the elemental composition of geological and biological materials. Both reactor neutrons and 14 MeV neutrons have been used. Instrumental approach has been followed incorporating coincidence measurements. The system and the methodology have been discussed. The results for the 3 Canadian rock standards (SY-2, SY-3, MRG-1), a trachyte, 2 NBS SRMS (1571 Orchard leaves, 1577 Bovine liver) and an IAEA intercomparison sample, Animal Muscle H.4 have been given for 15–25 elements.     

Determination of silver in SOIL-7 standard reference material by NAA

IAEA standard reference material SOIL-7 has been analyzed by both instrumental NAA and radiochemical NAA using epithermal neutron activation. These analyses confirm the NAA value of Ag in the intercomparison SOIL-7 which disagrees with some AAS values. Further geostandards were included and compared with literature data.     

Quality system implementation in Member States of the IAEA

The International Atomic Energy Agency (IAEA), through its Technical Co-operation Programme, has supported the establishment of many nuclear analytical and complementary laboratories in Member States. This included the development of capabilities for the use of various nuclear analytical techniques that include alpha, beta, and gamma spectrometry; radiochemical analysis; neutron activation analysis; energy dispersive X-ray fluorescence analysis; and total reflection X-ray fluorescence. As economic, ecological, medical, and legal decisions are frequently based on laboratory results, they need to be based on accepted national and international standards.The IAEA has taken up this important issue to enhance and foster the competitiveness of nuclear analytical laboratories with the consideration that non-nuclear capabilities are equally important. The projects aim at enhanced quality awareness, a concise system for documentation, establishment of standard operating procedures, procedures for validation of methods, surveillance of method performance, systems for sample management, regular qualification of personnel, client liaison and safety. These projects follow the ISO/IEC 17025 standard and promote participating laboratories to maintain a self-sufficient quality system by which they might be able to obtain national accreditation.This contribution describes the general concept of these projects and discusses some of the results achieved.     

Method validation procedures for environmental radiochemical measurements at AECS

The present paper describes the experience of the Atomic Energy Commission of Syria in relation to the application of Eurachem Guide on method validation for environmental radiochemical measurements. Methods validated include gamma and alpha spectrometry for natural and artificial radionuclides determination, and fluorometry determination for total uranium. Documents and records were first set to meet trackability and traceability requirements, where internal quality control mechanisms have been adopted. Methods stability was checked by means of Z-score control charts. Internal method validation parameters including method detection limits, repeatability limits, reproducibility limits, recovery coefficient and relative error were estimated. External method validation has been achieved by participating in international intercomparison exercises and proficiency tests organized by EML, IAEA and WU; some results of these activities are presented. Moreover, the application of both internal and external method validation gave the analysts in our laboratories more confidence in their skills, and it was of great assistance for our customers including regulatory authorities to evaluate the fitness of the method for their applications according to internationally agreed procedure. The steps followed here can be used for method validation in other laboratories with similar applications.     

Certification of trace and major elements and methylmercury concentrations in a macroalgae (Fucus sp.) reference material, IAEA-140

A marine reference material, IAEA-140, prepared with a macroalgae (Fucus sp.) was recently produced by the International Atomic Energy Agency and certified for trace and major elements and for methylmercury (MeHg). Certification of this material was achieved as an outcome of an international analytical intercomparison study which resulted in 116 independent sets of results reported by participants from 54 countries. The statistical evaluation of the collected data and the criteria used for assignment of the mean and uncertainty values are described. The analysis of data allowed to certify concentration values for 24 elements and MeHg, and to provide information values for another 10 elements. Regarding the elements which could be given certified values, between two and eight different instrumental methods were used to measure metal concentrations, and four independent analytical procedures were used to measure MeHg concentrations. In order to assess the results of the certification procedure, a comparison was made between the certified values obtained from the world-wide intercomparison results and the values obtained from a small subgroup of well-qualified laboratories. The means and 95% confidence intervals for reference values obtained by the two methods are similar for most elements showing that the usual method of certification used by the IAEA, based on large groups of participants, is indeed pertinent.     

Freshwater suspended particles: An intercomparison of long-term integrating sampling systems used for environmental radioactivity monitoring

Summary Sampling and sample preparation are known to carry large, but typically unknown uncertainty contributions to the final analytical data and there is a lack of qualitative and quantitative data on the comparability of results achieved by different sampling methods. To this end an intercomparison exercise was carried out to compare different methods for the collection of suspended material used for the monitoring of environmental radioactivity in freshwater bodies.This paper presents the results of this intercomparison exercise in which “in situ”particulate sampling devices were compared in field exercises performed in the Kiev Reservoir (Ukraine) and in the Po River (Italy). The main criterion for this intercomparison was the agreement among the¹³⁷Cs activity concentrations associated with the suspended particles expressed as Bq^. g^-1and among the (C/N) molar ratios measured on the suspended particles. In addition, an estimate of the uncertainties associated with each measuring method has been performed.