Conclusions of the workshop

The development of analytical techniques for the determination of chemical species has been one of the fastest growing features of the 90's in analytical chemistry. The need for good quality control of these determinations has led the Measurements and Testing Programme (BCR) to organize several series of interlaboratory studies in the field of speciation analysis over the last five years. The state of the art of speciation analysis was discussed at a first workshop in 1990 (Arcachon, F) and, at this stage, it was deemed necessary to discuss the progress achieved and the trends which should be developed in the near future. A workshop on Trends in Speciation Analysis was therefore held in Rome in February 1994, which allowed recommendations to be made based on round-table discussions. This paper gives a summary of these recommendations in the field of inorganic speciation. Projects currently undertaken in the field of inorganic speciation within the Measurements and Testing Programme are also described. An outline of the programme along with the panel of experts participating in this workshop is given in the appendix.     

Conclusions of the workshop

The development of analytical techniques for the determination of chemical species has been one of the fastest growing features of the 90's in analytical chemistry. The need for good quality control of these determinations has led the Measurements and Testing Programme (BCR) to organize several series of interlaboratory studies in the field of speciation analysis over the last five years. The state of the art of speciation analysis was discussed at a first workshop in 1990 (Arcachon, F) and, at this stage, it was deemed necessary to discuss the progress achieved and the trends which should be developed in the near future. A workshop on Trends in Speciation Analysis was therefore held in Rome in February 1994, which allowed recommendations to be made based on round-table discussions. This paper gives a summary of these recommendations in the field of inorganic speciation. Projects currently undertaken in the field of inorganic speciation within the Measurements and Testing Programme are also described. An outline of the programme along with the panel of experts participating in this workshop is given in the appendix.     

Single and Sequential Extraction in Sediments and Soils

Abstract

The determination of extractable trace metal contents in soils and sediments is currently performed in many laboratories to assess the bioavailable metal fraction (and related potential phyto-toxic effects) and the importance and possibility of mobilization of trace metals from polluted soil, sludge and sediment upon landfill application. Single and sequential extraction schemes are used for the assessment of the different “forms” of trace metals (e.g. “mobile/bioavailable”, “carbonate-bound” etc.). The lack of uniformity in the different extraction procedures used throughout the world does not allow the results to be compared or the procedures to be validated which has led to many criticisms in the past few years. Moreover, the lack of suitable reference materials for this type of operationally defined determinations did not enable the quality of the measurements to be controlled. Owing to the need for establishing common schemes for single and sequential extractions as well as for the improvement of the quality of extractable trace metal determinations in soil and sediments, the Community Bureau of Reference (BCR) has organised a project which results along with the state of the art of extractable trace metal determinations, use and applicability of extraction schemes and analytical limitations were decided to be thoroughly discussed in a workshop. This paper presents its main conclusions.     

Analytical quality control program used by the trace elements in foods and diets sub-network of the FAO European cooperative network on trace elements

Summary The analytical quality control program employed by the ongoing FAO study on 14 trace elements in nationally representative staple foods of European countries is presented. The analytical quality control used is based on: 1) precautions taken to avoid trace element contaminations or losses during sampling and sample handling; and, 2) on methods used to guarantee that the actual determinations yield correct results. The precautions are presented. A number of certified biological reference materials (RMs) were used to validate the analytical methods employed. The following staple food RMs were also prepared: wheat flour, potato powder, animal muscle (pork) and milk powder. They were tested for homogeneity and subjected to an interlaboratory comparison study on the basis of which recommended values for trace element concentrations were defined. Further, the mean relative standard deviation for the 95% confidence limits of the medians in all RMs was below 5% for Ca, Mg and Zn; below 10% for Mn; below 15% for Fe, Cu and Se; and below 25% for Mo and Ni. These RMs were used to control the analytical quality of the trace element determinations in the actual samples. It is concluded that important contaminations were avoided in sampling and sample handling and that use of the RMs described was necessary to guarantee the analytical quality of the results.     

Characterization (certification) of Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials for essential and toxic major, minor and trace elemental constituents

Summary Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods by analysts in cooperating laboratories yielded 10–29 best estimate and 1–16 informational concentration values for each of these materials. Two materials, Corn Starch and Microcrystalline Cellulose, contain particularly low levels of trace elements. These reference materials are intended for analytical quality control of elemental determinations in corn and plant products as well as other agricultural/food materials with related matrices.Contribution No. 92–146 from Centre for Land and Biological Resources Research     

Characterization (certification) of Bovine Muscle Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415) and Whole Milk powder (NIST RM 8435) Reference Materials for essential and toxic major, minor and trace element constituents

Summary Bovine Muscle Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415) and Whole Milk Powder (NIST RM 8435) Reference Materials were characterized for essential and toxic major, minor and trace element composition in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods yielded best estimate concentration values for 27, 23 and 21 elements, and informational concentration values for 5, 4 and 9 elements, respectively, in RM's 8414, 8415 and 8435. These Reference Materials are intended for analytical quality control of element determinations on meat, egg and milk-based products as well as agricultural/food materials with related matrices.Contribution no. 92–147 from Centre for Land and Biological Resources Research     

Advances in organic–inorganic hybrid sorbents for the extraction of organic and inorganic pollutants in different types of food and environmental samples

The efficiency of the extraction and removal of pollutants from food and the environment has been an important issue in analytical science. By incorporating inorganic species into an organic matrix, a new material known as an organic–inorganic hybrid material is formed. As it possesses high selectivity, permeability, and mechanical and chemical stabilities, organic–inorganic hybrid materials constitute an emerging research field and have become popular to serve as sorbents in various separaton science methods. Here, we review recent significant advances in analytical solid‐phase extraction employing organic–inorganic composite/nanocomposite sorbents for the extraction of organic and inorganic pollutants from various types of food and environmental matrices. The physicochemical characteristics, extraction properties, and analytical performances of sorbents are discussed; including morphology and surface characteristics, types of functional groups, interaction mechanism, selectivity and sensitivity, accuracy, and regeneration abilities. Organic–inorganic hybrid sorbents combined with extraction techniques are highly promising for sample preparation of various food and environmental matrixes with analytes at trace levels.     

Recent advances in the determination of the platinum group elements and gold

Accurate determinations of the platinum group elements (PGEs) and gold, known as the precious metals, have always been difficult tasks. The metals are often present at trace levels in sample types of complex composition. This situation has improved recently due to developments of instrumental methods and their applications to analyses of the precious metals in a variety of matrices. Attention has been given to determinations of traces of precious metals in biological, clinical and environmental samples. Foremost in importance is inductively coupled plasma mass spectrometry (ICP-MS) which has provided a sensitive means of simultaneous determination of traces of PGEs and gold. Important extensions and improvements in atomic absorption spectrometry (AAS), nuclear and electrochemical methods have been reported also. More research on sample treatments, especially fire assays, applied to PGEs has been carried out. Chlorination has proven to be a viable alternative to fire assays for preconcentration of PGEs and gold in analyses of geological materials. In addition, the recent availability of some additional reference materials will be of great assistance in research work on precious metals.     

Characterization (certification) of three wheat flours and a wheat gluten reference material (NIST RM 8436, 8437, 8438 and 8418) for essential and toxic major, minor and trace element constituents

Summary Three wheat flours, Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437), Soft Winter Wheat Flour (NIST RM 8438) and Wheat Gluten (NIST RM 8418) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition by analysts in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods yielded 16–27 best estimate and 3–8 informational concentration values for each of these materials. These reference materials are intended for analytical quality control of element determinations in flour and flour products as well as other agricultural/food materials with related matrices.Contribution No. 92–145 from Centre for Land and Biological Resources Research     

Certified reference materials of soils and sewage sludges for the quality control of trace element environmental monitoring

For the wide variety of soil/sludge matrices encountered in analytical practice, a range of CRMs should be available to verify the analytical quality control of any determination carried out, using samples which should be as similar as possible to real soil and sludge samples so that the method's performance may be tested under real analytical conditions. This paper presents basic requirements for the preparation of soil and sludge CRMs for the quality control of trace element determinations (total and extractable contents, following strict extraction protocols), and gives recent examples of new certifications successfully concluded by the SM&T programme of the European Commission.     

Rapid Methods in Analytical Chemistry

This article presents the most recent research in analytical chemistry concerning the development of rapid methodologies covering the period from 2009 up until today. In this context, different useful analytical methods have been developed based mainly on typical techniques such as gas chromatography, liquid chromatography, mass spectrometry, electrophoresis, electroanalytical chemistry, and biosensors. The analytical features of these methods have allowed the analysis of samples of different natures, such as environmental, food, pharmaceutical, and biological type, in which wide classes of analytes are promptly determined. The main advantages of these methods are included and discussed in this review regarding novelty, rapidity, sensitivity, selectivity, and costs. It is concluded that the development of rapid methods is still a growing trend in analytical chemistry and that gas- and liquid-chromatography mainly coupled to different modes of mass spectrometry are the most common analytical techniques applied today. Regarding the matrices analyzed, most of the methods have been developed for food analysis, followed by biological and environmental matrices.     

CRMs for quality control of determinations of chemical forms of elements in support to EU legislation

The concern for the control of toxic chemical forms of elements in the environment is reflected by an increasing number of analyses performed by research and routine laboratories. The European Commission has recognised the need to include some of these species in the list of dangerous substances to be monitored, e.g. in the marine environment or in groundwater. However, in most cases, the specifications are far from being sufficient in respect to the chemical forms of the element to be determined. Furthermore, these determinations are in most cases based on multi-step analytical techniques which are often prone to errors (e.g. at the extraction, derivatization or separation steps). Certified reference materials (CRMs) certified for their content in chemical forms of elements are, therefore, necessary to ensure the accuracy of these measurements and hence the respect of the regulations. However, the lack of CRMs for speciation analysis hampers the quality control of determinations which in turn leads to an incomparability of data produced; so far the number of CRMs produced by international organisations, e.g. NIST (USA), NIES (Japan), NRCC (Canada) and BCR (Belgium), is very limited and concerns mainly compounds such as e.g. methyl-mercury and butyltin compounds in biological matrices or sediments. The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a series of projects for the improvement of speciation analysis in environmental matrices, the final aim of which being the production of a variety of environmental CRMs. The existing EU legislation involving chemical forms of elements is presented, the requirements for the preparation of CRMs for speciation analysis are discussed and an update of the most recent CRMs produced within the Standards, Measurements and Testing Programme (SM&T) is given.     

CRMs for quality control of determinations of chemical forms of elements in support to EU legislation

The concern for the control of toxic chemical forms of elements in the environment is reflected by an increasing number of analyses performed by research and routine laboratories. The European Commission has recognised the need to include some of these species in the list of dangerous substances to be monitored, e.g. in the marine environment or in groundwater. However, in most cases, the specifications are far from being sufficient in respect to the chemical forms of the element to be determined. Furthermore, these determinations are in most cases based on multi-step analytical techniques which are often prone to errors (e.g. at the extraction, derivatization or separation steps). Certified reference materials (CRMs) certified for their content in chemical forms of elements are, therefore, necessary to ensure the accuracy of these measurements and hence the respect of the regulations. However, the lack of CRMs for speciation analysis hampers the quality control of determinations which in turn leads to an incomparability of data produced; so far the number of CRMs produced by international organisations, e.g. NIST (USA), NIES (Japan), NRCC (Canada) and BCR (Belgium), is very limited and concerns mainly compounds such as e.g. methyl-mercury and butyltin compounds in biological matrices or sediments. The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a series of projects for the improvement of speciation analysis in environmental matrices, the final aim of which being the production of a variety of environmental CRMs. The existing EU legislation involving chemical forms of elements is presented, the requirements for the preparation of CRMs for speciation analysis are discussed and an update of the most recent CRMs produced within the Standards, Measurements and Testing Programme (SM&T) is given.     

Development and applications of single-drop microextraction for pesticide residue analysis: A review

Single-drop microextraction (SDME) has become more popular than other microextraction techniques because it is simple, cost-effective, easy to operate and nearly solvent-free. The technique has been employed successfully for trace analysis in environmental, biomedical and food applications. In view of the increasingly stringent regulatory limits for many pesticides, which are below the LOD of the existing instruments, SDME may provide a cost-effective solution for reducing the LOD of pesticides. The present review focuses on recent development in SDME technique, and its application coupled with various analytical techniques, such as GC-MS, GC and HPLC for pesticide residue analysis in different matrices. The advantages, limitations and outlook on the future of SDME technique for its wider applications are also discussed.     

Projects for the improvement of the quality of chemical speciation analyses in environmental matrices

Summary The release of organometallic compounds and other chemical forms of elements in the environment has caused great concern because of their possible high toxicity. To validate the analytical techniques, the Community Bureau of Reference (BCR) has undertaken a series of projects for the improvement of the quality of determinations of chemical species in environmental matrices. The implementation of these projects follows a stepwise approach involving intercomparisons to detect and remove sources of errors in different phases of the analytical methods and the certification of the compounds in various matrices. The current projects deal with the determination of the extractable content of trace metals in soils (single extraction) and sediment (sequential extraction), forms of aluminium in water, elements with different oxidation states (e.g. As, Cr and Se) and organic forms (e.g. methylated forms of As in solution, methyl-mercury in fish, arseno-betaine and -choline in solutions, triethyl- and trimethyl-Pb compounds in solution, and butyltin compounds in sediment).Abbreviations AAS atomic absorption spectrometry - CVAAS cold vapour AAS - DPP differential pulse polarography - ECD electron capture detector - ETAAS electrothermal AAS - FIA flow injection analysis - FID flame ionisation detector - FLUOR spectrofluorimetry - FPD flame photometric detector - GC gas chromatography - HG hydride generation - HPLC high performance liquid chromatography - HPLC-AES HPLC atomic emission spectrometry - INAA instrumental neutron activation analysis - ICPAES Inductively coupled plasma AES - MS mass spectrometry - QFAAS quartz furnace AAS - RNAA neutron activation analysis with radiochemical separation     

Analysis of enantiomers in biological matrices by charged cyclodextrin-mediated capillary zone electrophoresis in column-coupling arrangement with capillary isotachophoresis

The possibility to apply charged chiral selector as buffer additive in capillary zone electrophoresis (CZE) on-line coupled with capillary isotachophoresis (CITP) was studied. Enantioseparations and determinations of trace (ng/ml) antihistaminic drugs [pheniramine (PHM), dimethindene (DIM), dioxopromethazine (DIO)] present in samples of complex ionic matrices (urine) served as model examples. A negatively charged carboxyethyl-β-cyclodextrin (CE-β-CD) was used as a chiral selector in analytical CZE stage following upon a sample pretreatment by CITP (preconcentration of the analytes from 5 to 20-times diluted urine samples, partial sample clean up removing macroconstituents from the sample matrices). A high recognition capability of the oppositely charged CE-β-CD was demonstrated by enantioselective retardation of the drugs in presence of micro-and semi-macroconstituents migrating in CZE stage and detectable by UV detector. In this way, enantiomers of the drugs could be easily separated and determined. Due to lack of interferences between the drugs and sample-matrix constituents in presence of charged CE-β-CD, demands on both spacers in CITP step and multiple column-switching were minimized. CITP-CZE method with charged selector appeared to be a useful analytical approach for the trace enantiomers in complex ionic matrices as it combined enhanced separation selectivity and sample loadabitlity with high separation efficiency and provided favorable performance parameters including sensitivity, linearity, precision, accuracy/recovery and robustness with minimal demands on sample preparation. Analysis of urine sample taken from a patient treated by PHM, showing concentration profile of PHM enantiomers and their metabolites, illustrated potentialities of the method in clinical research.     

A programme to improve the quality of butyltin determinations in environmental matrices

One of the major prerequisites for the certification of various analytes in different Certified Reference Materials (CRMs) is that the analytical methods used are of verified performance and, hence, that no systematic errors have been left undetected. In the case of difficult measurements, research and feasibility studies are often necessary to ensure that the methods are operating under good quality control. The EC Standards Measurements and Testing Programme (SMT, formerly BCR) usually follows a step-by-step approach which consists in series of interlaboratory studies to assess and improve the quality of measurements prior to certification by comparing different analytical techniques. A programme following such stepwise approach has started in 1987 with the aim of improving the quality of butyltin determinations in environmental matrices. The project involved ca. 20 laboratories from different Member States of the European Union. The first interlaboratory study dealt with simple solutions containing mixtures of organotin compounds and a second exercise focused on the analysis of a tributyltin-spiked sediment. These exercises were continued by two certifications on butyltins in sediment, the first of which could not be successfully concluded owing to the high spread of results observed between the results of different techniques. The second certification allowed a CRM certified for its contents of di- and tributyltin (CRM 462) to be produced. This programme on Sn speciation is now focusing on the certification of butyltin and phenyltin compounds in candidate CRMs of mussel and sediment. This paper gives an account of the step-by-step approach followed and presents the results of the two certification exercises carried out so far. The preparation of the mussel candidate CRM is also described.     

Trace analysis of per- and polyfluorinated alkyl substances in various matrices-How do current methods perform?

Per- and polyfluorinated alkyl substances (PFAS) are a group of industrial chemicals, some of which have been produced for over 50 years. Scarcely one decade ago, their ubiquity in wildlife, humans and the global environment was discovered. This urged the need for robust and reliable, yet very sensitive analytical methods allowing for their determination in various matrices. This article reviews the state-of-the-art in trace analysis of ionic and neutral PFAS in humans as well as environmental samples such as wildlife, water, solid matrices and air. Analytical protocols for PFAS determination in food and consumer products are also included. The methods are critically discussed in terms of their advantages, shortcomings, possibilities, limitations, and potential for further development.     

Analytical methodologies for the determination of nitroimidazole residues in biological and environmental liquid samples: A review

Nitroimidazoles (NDZs) are antiprotozoal drugs that are typically used in veterinary and human medicine. NDZs and their metabolites are believed to possess genotoxic, carcinogenic and mutagenic properties, and this is (one reason) why their use has been banned within the European Union. Hence, the determination of trace residues of these substances in edible animal tissues has been of growing concern over the past few years. Even, though there has been a need to develop sensitive and reliable analytical methods to study the residues of these compounds in different matrices, available methodologies in environmental samples are rather limited. These and other pharmaceutical compounds have become one of the most important new classes of environmental pollutants that have been detected in wastewater-treatment-plant (WWTP) effluents, receiving waters, drinking water and groundwater. A compilation of the most representative analytical methodologies for the determination of NDZ residues during the last decade is presented in this paper. Its scope is the two main areas which require their determination, namely biological and environmental matrices. A detailed explanation of both areas, including sample treatment and detection systems, and future trends is presented, focusing on the difficulties of confirming analytes at low concentration levels.