CHAPTER 1
Introduction
Sound, accurate and reliable measurements, be they physical, chemical or biological in nature, are essential to the functioning of modern society. Without them, industries, particularly high technology ones, cannot operate, trade is impaired by disputes, healthcare becomes empirical and legislation, ranging from environmental and worker protection to the operation of the Common Agricultural Policy and the Single Market, cannot be successfully implemented. For these reasons, advanced nations spend up to 6% of their GNP on measurements and measurement related operations.
Measurements hence affect the daily lives of every European citizen. Often the results of measurements or chemical analyses are taken for granted, e.g. in our direct contact with measuring devices when we buy food or consume gas and electricity at home. The importance of accurate measurements creates particular concern in specific cases, e.g. when food is tested to check whether it has been contaminated by poisonous substances or when blood is analysed as part of a hospital check-up.
It is precisely because measurements affect everyone that regulations (either national or European) are established in order to ensure that the measurements and chemical analyses are performed in a reliable way and therefore that consumer interests are properly protected. The need for harmonization of measurement systems has been recognized – some of them centuries ago – e.g. the verification of weights and measures to ensure fair trades and the adoption of the metric system now known as "Système International" (SI).
A considerable number of measurements are, of course, not directly evident to the general public. These concern the quality of products which determine, for example, the prices of food and/or feedstuffs; this quality is not open to bargaining but must be measured with the same accuracy and reliability in every country so that arguments about a product's acceptability are avoided and hence that a proper functioning of the Single Market may be ensured.
1.1 Need for Method Performance Evaluation
The harmonization of measurements and technical specifications is a continuous process, and is achieved either by means of Community Directives or the establishment of European Norms. However, this does not solve all the problems. Indeed, the measurements and analyses required for the implementation of these Norms and Directives are sometimes so difficult that, even when applying the same method, laboratories may still find very different results. It is obvious that such a disagreement between laboratories does not allow the Norms and Directives to be respected and therefore these have no harmonization effects. As a consequence, measures to evaluate and guarantee the quality of a laboratory's performance were established involving quality assurance rules and guidelines (e.g. Good Laboratory Practice, ISO 9000 and EN 45000 standard series), accreditation systems and the production of certified reference materials (CRMs).
Quality issues related to analytical measurements have been described in full detail in several books [1–3] and highlighted several principles, e.g. validation of methods, quality assurance protocols incorporating the use of CRMs, independent assessment of method performance by participation in proficiency testing schemes, and accreditation. Method performance studies also represent a very important aspect to evaluate the state-of-the-art of a particular type of analysis at the development stage (e.g. for testing the applicability of a standard method) or to improve the quality of measurements, e.g. prior to the certification of reference materials.
1.2 EC Initiatives Related to Measurement Quality
In order to eliminate disputes arising from doubtful measurements, the Commission of the European Communities established the Community Bureau of Reference (BCR) about 25 years ago to encourage and support technical collaboration between the laboratories of EC Member States. In this way, the Community helped laboratories in the Member States to provide accurate and reliable measurements in those sectors which are vital to the Community as a whole: trade, agriculture, food, industrial products, environment, health and consumer protection [4].
This collaborative effort on measurements was substantially increased within the second Framework Programme (Applied Metrology and Chemical Analysis, 1987–1992). It was likely to expand since the Community had embarked on an ambitious programme to unify its internal market. Major efforts were indeed required to harmonize a wider range of technical standards and measurements throughout the Community so that companies could be sure they were competing on equal terms in each Member State. In this context, it became essential that the accuracy of results be proven wherever the measurements or analyses were performed. The establishment of laboratory networks was a successful tool for the improvement of the quality of a wide variety of measurements performed in Europe. In turn, these collaborative efforts facilitated European cohesion.
To pursue this action within the Third Framework Programme (1990–1994), the European Community has implemented the Measurements and Testing programme which, by addressing the issues highlighted above, aimed to contribute to the harmonization and improvement of methods of measurement and analysis when these methods were not sufficiently accurate and laboratories obtained differing results. Through this harmonization, the programme aimed to contribute to the ease of circulation of agricultural and industrial products in the Community, to improvements in the means of monitoring environment and health and to the resolution of the new challenges faced by industry. The aims of the Measurements and Testing programme were also to improve the competitive position of European industry by promoting industrial innovation, to support pre-normative research and other technical support necessary for the development and application policies (Internal Market, environment, agriculture, health, etc., and support to activities of CEN, CENELEC, ETSI, etc.) and to support the further development of the measurement infrastructure of Europe (coordination of national activities, promotion of good measurement practices throughout Europe, etc.) [5].
The Measurements and Testing Programme has developed into a wider programme called Standards, Measurements and Testing (SM&T) within the Fourth Framework Programme (1994–1998). This programme aims, through research and technological developments, to improve the competitiveness of all sectors of European industry, to support the implementation of Community policy and to meet the needs of society [6]. The main targets are:
• To improve the competitive position of all sectors of European industry (including SMEs) by promoting better measurements at the research and development levels, better definition and control of the quality of products, more efficient in-process measurements and technical assistance to the mutual recognition of certificates in accordance with the Global Approach to Conformity Assessment
• To promote research and other technical support necessary for the development and implementation of other Community policies (Single Market, environment, agriculture, health, transport and protection of the Community's external frontiers)
• To promote research in support of the activities of CEN, CENELEC, ETSI and other European bodies which seek to maintain or establish quality standards via either new and existing written standards or codes of practice
• To support the further development of the European measurement infrastructure by facilitating the coordination of national activities, the development of measurement standards, of advanced methods and systems and the mutual recognition of results and accreditation systems
• To promote the dissemination and application of good measurement practice throughout Europe, particularly in the less favoured regions, for example, by the organization of training courses and by the establishment of networks.
From this description, it is obvious that the SM&T programme is mainly oriented towards support to European industry and Community legislation. The selection of projects is carried out through a system of time-limited calls for proposals which are regularly published in the Official Journal of the European Communities. The types of projects generally funded are of four types:
• Interlaboratory studies carried out by consortia of European laboratories, of which the aim is improve the state-of-the-art of different types of measurements [7]. These projects are useful to detect possible sources of errors related to particular techniques, to create networks of laboratories within the European Union and to prepare groups of expert laboratories for the certification of reference materials
• The certification of reference materials is the traditional BCR activity [8] which is still continuing within the SM&T programme [9]. These collaborative projects enable the production of reference materials certified in a reliable manner, which are necessary for the verification of the accuracy of analytical methodologies in various sectors (e.g. environment, food and agriculture, biomedical)
• Development of new methods and instrumentation became one of the core activities of the SM&T programme. These developments concern innovative instruments necessary to improve the quality of measurements in particular sectors (e.g. on-line measurement techniques, field -measurement methods etc.) [10]
• Pre-normative research is undertaken to test the feasibility of standards (e.g. through interlaboratory studies or method development) prior to their implementation by official normalization bodies (e.g. CEN, CENELEC, ISO). The same type of projects may be performed to test the requirements of draft EC Directives prior to their establishment [10].
1.3 Improving the Quality of Speciation Analysis
As illustrated by Chapter 2, speciation is one of the growing features of analytical chemistry of the 1990s. It is known that the determination of total trace element contents in environmental monitoring, toxicity studies, etc., is no longer sufficient for the understanding of biogeochemical pathways of trace elements which depend on specific chemical forms (e.g. different oxidation states, organometallic compounds, etc.). Owing to the number of analyses performed by a wide range of EC laboratories, the SM&T programme has recognized the need to launch collaborative projects to establish and improve the state-of-the-art of speciation analysis in Europe. This book presents an overview of these projects which were undertaken over the past 10 years to improve the quality control of speciation analysis in various environmental matrices. The different chapters illustrate the aims of the programme and the above-mentioned activities. In particular, the results of all the interlaboratory studies which were carried out prior to certification campaigns of a series of chemical species (e.g. tributyltin, methylmercury) are described; the chapters also include a full description of the preparation of candidate reference materials (RMs) and of the certification results, as well as the development of new analytical techniques which were necessary in the course of certification (e.g. supercritical fluid extraction, isotope dilution mass spectrometry).
Chapter 2 discusses several aspects of speciation analysis, e.g. definitions, existing regulations and sources of errors likely to occur at various steps of the analytical procedures. It is followed by Chapter 3 describing general principles of improvement schemes (organizational aspects) and basic requirements to be followed for the certification of reference materials.
Specific chapters then focus on different projects on speciation analysis. Chapter 4 deals with interlaboratory studies on methylmercury in fish and sediment; Chapter 5 describes the collaborative projects to certify organotins in sediment RMs and mussel tissues; Chapter 6 gives an overview of the certification project on trimethyllead in simulated rainwater and urban dust; Chapter 7 describes the certification project on arsenic species in fish tissues; Chapter 8 focuses on the intercomparison and tentative certification of Se(IV) and Se(VI) in simulated freshwater; Chapter 9 deals with a feasibility study to stabilize Cr species in solution followed by the certification of Cr(III) and Cr(VI) in lyophilized solutions and welding dust; Chapter 10 gives a review of methods used for A1 speciation; Chapter 11 develops the overall collaborative project to standardize single and sequential extraction procedures for soil and sediment analysis, followed by interlaboratory studies and certification of soil and sediment reference materials.
CHAPTER 2
Speciation Analysis of Environmental Samples
The number of determinations of chemical species in environmental matrices carried out in routine and research laboratories has increased considerably in the last few years. However, the quality of the results has often been neglected in environmental, food and biomedical analyses. Good reproducibility of an analysis is not sufficient. It helps, of course, to make results comparable over a limited area or a limited period ("trend" monitoring), but for a full comparability of results over time and location, and thus for a solid and universal interpretation of the findings, accuracy is a must; this has been widely demonstrated in the literature (e.g. [8,13,14]). Too many scientists have stated that good reproducibility in time was sufficient to follow trends and demonstrate the effects of actions taken by authorities to improve the quality of the environment or food. Such statements overlook modelling applications, theory development, etc., and ignore improvements in equipment and methodology.
To achieve not only good reproducibility but also good accuracy, various measures are necessary. It is clear that good Quality Control (QC) of speciation analyses has not yet been achieved. Typical examples illustrate the lack of accuracy that may occur in the determination of inorganic [14] and organic traces [15] in environmental matrices. These examples are by no means selected but occur quite commonly in many fields of analysis, including the determination of species in environmental matrices. When results differ so much, they are not trustworthy. Moreover, in the past, too many wrong but highly reproducible results have lead to misinterpretation of environmental processes.
In the past few years, the determination of chemical species of elements (e.g. As, Hg, Sn species) has become of increasing concern due to their high toxic impact (see a review from Craig [16]). Some of these compounds (e.g. methylmercury, tributyltin) are now included in the black list of compounds to be monitored in the marine environment according to an EEC Directive (amendment of the Directive 76/464/EEC). Consequently, a wide variety of analytical techniques have been developed recently and are described in the literature, e.g. for Sn speciation [17,18], As speciation [19], Hg speciation [20], Pb speciation [21] and Se speciation [22].
Analytical techniques used for the determination of chemical species are generally based on a succession of steps (e.g. extraction, separation, detection) which enhance the risks of errors. This chapter gives an overview of the different types of errors that may occur in speciation analyses.
2.1 Definitions
The term "speciation" is used for a wide variety of analyses, ranging from the determination of well defined "species", e.g. oxidation states of elements or organometallic compounds, to forms of elements which are operationally defined (i.e. related to an extraction procedure) and which are quoted as "bioavailable", "mobile", etc., forms of elements. A recent definition has been given by Hetland et al. who described speciation as "a specific form (monoatomic or molecular) or configuration in which an element can occur, or a distinct group of atoms consistently present in different matrices" [23]; the official definition is presently in discussion within IUPAC. This definition tends to restrict the term "speciation" to well-identified chemical forms of elements. However, the use of this term is much wider, which creates some confusion among scientists. The confusion is even greater when legislation is approached since, at a certain level, nobody can explain what is the difference between "bioavailability", "bioaccumulation", "essentiality", "lethal effect", etc. It should now be time for the scientific community to use clearer terminology in relation to speciation to avoid any misunderstanding; this has been well understood by scientists working in the field of organic analysis who defined specific terms in relation to different compounds or families of compounds, e.g. in the case of chlorinated biphenyls or poly aromatic hydrocarbons. Therefore, a trend that should be adopted in speciation analysis would be to specify clearly the actual forms which are determined, i.e. not speaking any more about the speciation of a given element (unless referring to a particular type of analysis in general terms as used in organic analysis, e.g. mercury speciation and polychloroaromatic hydrocarbon or chlorinated biphenyl determinations, respectively). With reference to elements with different oxidation states, an example can be the determination of inorganic selenite and selenate. With regard to organometallic species, the compounds may be referred to as cations or with their counter-ions: an example is tributyltin which could be referred to as TBT+ or with its respective anion (e.g. TBTC1, TBTAc), depending on the actual determination technique used. Concerning "extractable trace metals", the term speciation should not be applied since these operationally defined determinations (obtained from single and/or sequential extractions) define "groups" of trace elements without clear identification; these procedures represent a useful approach for environmental studies (in particular for soil and sediment) [24], but the comparability of the measurements is only possible provided that standardized protocols are used [25]. As soon as procedures have been accepted as a standardized method, the determinations should clearly refer to the actual measurements, e.g. EDTA-extractable or acetic acid-extractable trace elements, and not to unclear terms such as "bioavailable", "mobile", etc., which is rather an interpretation of the measurements than the exact terminology of what is measured [26].
