Institute For Reference Materials And Measurements Research Articles

Cadmium and lead distribution in pyrite ores

The pyrite ores are strategic industrial resources which generally serve as raw material for producing sulfuric acid. However, during the mining and industrial processing activities, associated toxic elements of cadmium (Cd) and lead (Pb) could be released into the surroundings, posing a significant threat to local environment and human health. In this study, the Institute for Reference Materials and Measurement (IRMM) sequential extraction scheme was used to investigate the geochemical fractionation of Cd and Pb in pyrite ores from a mining area located in Yunfu, western Guangdong, China. The results showed that most of Cd and Pb (>90%) were predominantly found in the geochemically mobile fractions, indicating that Cd and Pb were readily bioaccessible thus easily assimilated and accumulated by organisms. FESEM-EDS results showed that the studied pyrite ores were mainly composed of O, S, and Fe, while the XRD characterizations suggested that FeS2 and SiO2 were the major minerals. The high-resolution transmission electron microscope and element mapping characterization further confirmed that FeS2 was the main mineral of pyrite ores which contained relatively enriched toxic heavy metals (e.g., Pb and Cd). The findings highlight that an extremely large amount of geochemically mobile heavy metals can be released into the environmental media during the mining and utilization processes of pyrite ores based on IRMM sequential extraction protocol. Therefore, proper countermeasures against environmental risks of utilizing pyrite ores should be taken to mitigate the impacts on local ecosystem and human health.

Geochemical fractionation of thallium in contaminated soils near a large-scale Hg-Tl mineralised area

Enriched levels of thallium (Tl) in the environment are not only derived from anthropogenic sources but also have potential natural origins owing to Tl-rich sulphide mineralization. However, little is known regarding the geochemical fractionations of Tl in contaminated soils from geogenic sources. This study aims to reveal the Tl geochemical fractionations in different types of soils from a large-scale independent Tl mine in southwestern China, via a modified Institute for Reference Materials and Measurement (IRMM) sequential extraction (four-step) scheme. The results revealed that a large percentage of Tl was related to the labile portions (including reducible, weak-acid-exchangeable, and oxidizable fraction) of the soils (68.8–367 mg kg−1). Further analyses by Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectrometer (STEM-EDS) found that Tl mainly existed in the Fe-containing minerals (such as jarosite and hematite) with fine particles (∼1 μm). These results highlight that, apart from the anthropogenically induced Tl pollution, the naturally occurring Tl contamination in soils may also pose significant risks to human health and ecological safety. Owing to the relatively high mobility and bioavailability of Tl in the labile fractions, it is important to understand geochemical fractionations of this element for alleviating Tl pollution and effective management of naturally occurring Tl contaminated soils.

The mobility of thallium in sediments and source apportionment by lead isotopes

Thallium (Tl) is a very toxic heavy metal. As a part of ongoing investigations, the mobility, sources and fate of Tl were investigated for sediments from a watershed in the northern part of the Pearl River, South China, whose catchment has been seriously impacted by large-scale PbZn smelting activities onshore. A wide dispersion of severe Tl contamination was observed throughout the depth profiles. A modified IRMM (Institute for Reference Materials and Measurements, Europe) sequential extraction procedure of a selected depth profile uncovered an exceptionally high enrichment of Tl in geochemically-mobile fractions (i.e., weak-acid-exchangeable, reducible and oxidizable fractions), on average 5.94 ± 2.19 mg/kg (74.6% ± 5.1% of the total Tl content) not only in the surface sediments but also in deep sediments. The proximal quantitative source apportionment using Pb isotopic fingerprinting technique indicated that a majority (80%–90%) of Tl contamination along the depth profiles is anthropogenically derived from the PbZn smelting wastes. The results highlight the pivotal role of smelting activities in discharging huge amounts of geochemically-mobile Tl to the sediments down to approximately 1 m in length, which is quantitatively evidenced by Pb isotopic tracing technique. Lead isotopes combined with distribution of Tl and Pb contents identified a potential marker for a point source from the PbZn smelter in the river catchment, which also provides a theoretical framework for source apportionment of metal contamination in a larger river/marine system and in other sulfide mining/smelting areas likewise.

Rare earth elements profile in a cultivated and non-cultivated soil determined by laser ablation-inductively coupled plasma mass spectrometry

Rare earth elements (REEs) have several applications but the effects on environment are not well known. Therefore, the aim of this work is to establish a method for direct solid sample analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to evaluate the concentration and distribution of REEs in cultivated and non-cultivated soil. Samples were collected in two areas to 40 cm of depth. The LA-ICP-MS method is easy to be implemented and the sample treatment is very fast comprising only its drying, grounding and pressing as a pellet. The accuracy of the method was evaluated by using a certified reference material (BCR 667 – Estuarine Sediment, Institute for Reference Materials and Measurements (IRMM)) where good agreement with the certified values was obtained. Analyte recovery at two levels of concentration (2.5 and 15.0 μg g−1) was also performed and recoveries in the range of 85%–120% were achieved, values that are acceptable for LA-ICP-MS analysis. In general, the concentration of the REEs is higher in the cultivated soil and increased from the surface to deeper layers, which can be a consequence of fertilizer application.

A temperature-tolerant multiplex elements and genes screening system for genetically modified organisms based on dual priming oligonucleotide primers and capillary electrophoresis.

High throughput screening systems are the preferred solution to meet the urgent requirement of increasing number of genetically modified organisms (GMOs). In this study, we have successfully developed a multiplex GMO element screening system with dual priming oligonucleotide (DPO) primers. This system can detect the cauliflower mosaic virus 35S (CaMV 35S), terminator of nopaline synthase gene (NOS), figwort mosaic virus 35S (FMV 35S) promoter, neomycin phosphotransferaseII (NPTII), Bt Cry 1Ab, phosphinothricin acetyltransferase genes (bar) and Streptomyces viridochromogenes (pat) simultaneously, which covers more than 90% of all authorized GMO species worldwide. This system exhibits a high tolerance to annealing temperatures, high specificity and a limit of detection equal to conventional PCR. A total of 214 samples from markets, national entry-exit agencies, the Institute for Reference Materials and Measurement (IRMM) and the American Oil Chemists' Society (AOCS) were also tested for applicability. This screening system is therefore suitable for GMO screening.

Nuclear microprobe performance in high-current proton beam mode for micro-PIXE

The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I>100pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57μg/cm2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3MeV proton beam is presented.

Development of a Certified Reference Material for myeloperoxidase-anti-neutrophil cytoplasmic autoantibodies (MPO-ANCA)

A serum Certified Reference Material (CRM) for supporting reliable autoimmune diagnostics was recently released by the Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre of the European Commission. It was produced in collaboration with a Working Group on the Harmonisation of Autoimmune Tests of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC WG-HAT). This material is aimed at facilitating the standardisation of measurements of anti-myeloperoxidase immunoglobulin G antibodies. The CRM could be used as a common calibrant by clinicians and manufacturers thereby significantly improving the comparability of results from commercial immunoassays used for IgG anti-MPO measurements. This paper provides information on the new CRM and its intended use.

A colleague to remember

I realized that I have forgotten when I met Paul de Bievre for the first time. But I remember well how enthusiastically he was talking during one of my visits to the European Commission’s Institute for Reference Materials and Measurements (IRMM) more than 20 years ago. It was about interlaboratory comparisons based on independently established reference values and concepts for a very precise and commonly to be used terminology on measurements in chemistry. Since then I had very regular contacts with Paul. Not primarily at IRMM, despite his appointments there as Head of the Isotope Measurement Unit until 1998 and as Advisor to the Director until 2002 as well as his visits on IRMM’s Open Days and anniversary celebrations. I have rather discussed with him at conferences and meetings all over the world or at his home in Kasterlee (relatively close to the IRMM). For me Paul was one of the most prominent ambassadors for metrology in chemistry. He devoted his professional life, which definitely did not stop after his official retirement from the European Commission (did he retire at all?) to promote the comparability of measurement results and the common understanding of metrology among scientists. For that purpose he was a global traveler, missing only very few countries of the world, and an invited speaker at many conferences and seminars. Paul was always keen to stipulate what he called ‘clear thinking.’ This gained him in my eyes the label ‘Mister Terminology,’ in the combination of creating and promoting terms as well as underlying concepts. His contributions to the development of the International Vocabulary of Metrology (VIM) are certainly the most visible, but not the only signs of these efforts. When I joined committees or organizations such as CCQM, ISO/REMCO, Eurachem or CITAC, Paul had been already there. He had truly a ‘founding mentality’! Indeed, Paul has been recognized as one of the founding fathers of CIPM’s Committee on Metrology in Chemistry (CCQM), as co-founder of Eurachem and CITAC, and he was one of the founding editors of this journal Accreditation and Quality Assurance (ACQUAL). Many of his ACQUAL editorials, later published as ‘Paul’s Columns,’ were taken up by colleagues as education material or as stimulus for advancing metrological concepts and approaches further. They initiated also controversial debates and the & Hendrik Emons JRC-IRMM-ACQUAL@ec.europa.eu

Thallium dispersal and contamination in surface sediments from South China and its source identification

Thallium (Tl) is a non-essential element in humans and it is considered to be highly toxic. In this study, the contents, sources, and dispersal of Tl were investigated in surface sediments from a riverine system (the western Pearl River Basin, China), whose catchment has been contaminated by mining and roasting of Tl-bearing pyrite ores. The isotopic composition of Pb and total contents of Tl and other relevant metals (Pb, Zn, Cd, Co, and Ni) were measured in the pyrite ores, mining and roasting wastes, and the river sediments. Widespread contamination of Tl was observed in the sediments across the river, with the highest concentration of Tl (17.3 mg/kg) measured 4 km downstream from the pyrite industrial site. Application of a modified Institute for Reference Materials and Measurement (IRMM) sequential extraction scheme in representative sediments unveiled that 60–90% of Tl and Pb were present in the residual fraction of the sediments. The sediments contained generally lower 206Pb/207Pb and higher 208Pb/206Pb ratios compared with the natural Pb isotope signature (1.2008 and 2.0766 for 206Pb/207Pb and 208Pb/206Pb, respectively). These results suggested that a significant fraction of non-indigenous Pb could be attributed to the mining and roasting activities of pyrite ores, with low 206Pb/207Pb (1.1539) and high 208Pb/206Pb (2.1263). Results also showed that approximately 6–88% of Tl contamination in the sediments originated from the pyrite mining and roasting activities. This study highlights that Pb isotopic compositions could be used for quantitatively fingerprinting the sources of Tl contamination in sediments.

Thallium transformation and partitioning during Pb–Zn smelting and environmental implications

Thallium (Tl) is a toxic and non-essential heavy metal. Raw Pb–Zn ores and solid smelting wastes from a large Pb–Zn smelting plant – a typical thallium (Tl) pollution source in South China, were investigated in terms of Tl distribution and fractionation. A modified IRMM (Institute for Reference Materials and Measurement, Europe) sequential extraction scheme was applied on the samples, in order to uncover the geochemical behavior and transformation of Tl during Pb–Zn smelting and to assess the potential environmental risk of Tl arising from this plant. Results showed that the Pb–Zn ore materials were relatively enriched with Tl (15.1–87.7 mg kg−1), while even higher accumulation existed in the electrostatic dust (3280–4050 mg kg−1) and acidic waste (13,300 mg kg−1). A comparison of Tl concentration and fraction distribution in different samples clearly demonstrated the significant role of the ore roasting in Tl transformation and mobilization, probably as a result of alteration/decomposition of related minerals followed by Tl release and subsequent deposition/co-precipitation on fine surface particles of the electrostatic dust and acidic waste. While only 10–30% of total Tl amounts was associated with the exchangeable/acid-extractable fraction of the Pb–Zn ore materials, up to 90% of total Tl was found in this fraction of the electrostatic dust and acidic waste. Taking into account the mobility and bioavailability of this fraction, these waste forms may pose significant environmental risk.

Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

Establishment of detection methods for approved LMO in Korea

AbstractLiving modified organisms (LMO) are one of the most widespread products of modern biotechnology after DNA discovery. Due to the decline of grain self-sufficiency rate and the increase of reliance on LMO imports in Korea, a series of concerns with regard to safety of living modified(LM) crops has been raised. The aim of this study is to establish the detection methods for unintentional release or growing of LMO plants in environmental conditions. To detect LM crop events, general concepts of specific primer design and PCR conditions were provided by the Joint Research Centre (JRC). The certified reference materials of seven LM events (4 soybean, 2 cotton and 1 corn) were obtained from the Institute for Reference Materials and Measurements (IRMM) and the American Oil Chemists' Society (AOCS). Genomic DNA from seven LM events were purified and PCR amplifications were carried out by using individual event-specific primer sets. LM-specific PCR products of all seven events were efficiently amplified by our methods. The results indicate that the established detection method for LMOs is suitable as a scientific tool to monitor whether the crops found in natural environments are LMOs.

Neutron-induced fission cross section ofPu240from 0.5 MeV to 3 MeV

$^{240}\mathrm{Pu}$ has recently been pointed out by a sensitivity study of the Organization for Economic Cooperation and Development (OECD) Nuclear Energy Agency (NEA) to be one of the isotopes whose fission cross section lacks accuracy to meet the upcoming needs for the future generation of nuclear power plants (GEN-IV). In the High Priority Request List (HPRL) of the OECD, it is suggested that the knowledge of the $^{240}\mathrm{Pu}(n,f)$ cross section should be improved to an accuracy within 1--3 %, compared to the present 5%. A measurement of the $^{240}\mathrm{Pu}$ cross section has been performed at the Van de Graaff accelerator of the Joint Research Center (JRC) Institute for Reference Materials and Measurements (IRMM) using quasi-monoenergetic neutrons in the energy range from 0.5 MeV to 3 MeV. A twin Frisch-grid ionization chamber (TFGIC) has been used in a back-to-back configuration as fission fragment detector. The $^{240}\mathrm{Pu}(n,f)$ cross section has been normalized to three different isotopes: $^{237}\mathrm{Np}(n,f)$, ${}^{235}\mathrm{U}(n,f)$, and ${}^{238}\mathrm{U}(n,f)$. Additionally, the secondary standard reactions were benchmarked through measurements against the primary standard reaction ${}^{235}\mathrm{U}(n,f)$ in the same geometry. A comprehensive study of the corrections applied to the data and the associated uncertainties is given. The results obtained are in agreement with previous experimental data at the threshold region. For neutron energies higher than 1 MeV, the results of this experiment are slightly lower than the ENDF/B-VII.1 evaluation, but in agreement with the experiments of Laptev et al. (2004) as well as Staples and Morley (1998).

γ-ray production cross sections of inelastic neutron scattering on natural molybdenum

γ-ray production cross sections of inelastic neutron scattering have been measured for molybdenum using the (n,n’γ)-technique. The experiment was performed at the GELINA facility at the Institute for Reference Materials and Measurements (IRMM) with the Gamma Array for Inelastic Neutron Scattering (GAINS) setup. GAINS consisted of eight high purity germanium detectors at the time of this experiment. The sample was made of natural molybdenum, which includes seven isotopes (A = 92, 94, 95, 96, 97, 98, 100). The presence of so many isotopes in the sample leads to overlapping peaks in the spectra, which limits the amount of data that can be extracted from the analysis. Nevertheless, a total of 31 γ rays from the seven isotopes were analysed and γ-ray production cross sections were determined. Comparisons to other experimental results were made when such data was available. Also comparisons with model calculations were made with the Talys 1.6 code.

A QUANTITATIVE COMPETITOR PCR ASSAY TO DETECT GENETICALLY MODIFIED ROUNDUP-READY SOYBEANS IN COMMERCIALLY SOLD FOODS IN IRAN

Due to ever-increasing global diffusion and related socio-economic implications, the detection of genetically modified organisms (GMOs) is very important. In this study, we design a plasmid containing two genes in mutated form as construct-specific (cp4 epsps) and event-specific (pd35S). It is applied for quantitative-competitor (QC) PCR as a simple and reliable method for the detection of GM food. This plasmid is calibrated with the external standard of the IRMM (The Institute for Reference Materials and Measurements), and then used to detect the presence of cp4 epsps and pd35S sequences in five foods derived from GM round-ready (RR) soya sold commercially in Iran. The results indicate the presence of GM RR soya in these products, quantitatively. In order to detect whether they contain more or less than 1% RR soya DNA, QCPCR with various amounts of DNA plasmids as a standard was performed. The results show that this plasmid can be used as a calibrator for 1% cp4 epsps and pd35S, and that it can also be applied instead of 1% IRMM genomics.

Determination of total cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms: outcome of IMEP-116 and IMEP-39

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the International Measurement Evaluation Program (IMEP). IMEP organises inter-laboratory comparisons in support of European Union policies. This paper presents the results of two proficiency tests (PTs): IMEP-116 and IMEP-39, organised for the determination of total Cd, Pb, As, Hg and inorganic As (iAs) in mushrooms. Participation in IMEP-116 was restricted to National Reference Laboratories (NRLs) officially appointed by national authorities in European Union member states. IMEP-39 was open to all other laboratories wishing to participate. Thirty-seven participants from 25 countries reported results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study. Both PTs were organised in support to Regulation (EC) No. 1881/2006, which sets the maximum levels for certain contaminants in food. The test item used in both PTs was a blend of mushrooms of the variety shiitake (Lentinula edodes). Five laboratories, with demonstrated measurement capability in the field, provided results to establish the assigned values (Xref). The standard uncertainties associated to the assigned values (uref) were calculated by combining the uncertainty of the characterisation (uchar) with a contribution for homogeneity (ubb) and for stability (ust), whilst uchar was calculated following ISO 13528. Laboratory results were rated with z- and zeta (ζ)-scores in accordance with ISO 13528. The standard deviation for proficiency assessment, σp, ranged from 10% to 20% depending on the analyte. The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39.

Characterization of 235U Targets for the Development of a Secondary Neutron Fluence Standard

The MetroFission project, a Joint Research Project within the European Metrology Research Program (EMRP), aims at addressing a number of metrological problems involved in the design of proposed Generation IV nuclear reactors. As part of this project a secondary neutron fluence standard is being developed and tested at the neutron time-of-flight facility GELINA of the JRC Institute for Reference Materials and Measurements (IRMM). This secondary standard will help to reach the neutron cross section measurement uncertainties required for the design of new generation power plants and fuel cycles. Such a neutron fluence device contains targets for which the neutron induced cross section is considered to be a standard. A careful preparation and characterization of these samples is an essential part of its development. In this framework a set of 235U targets has been produced by vacuum deposition of UF4 on aluminum backings by the target preparation laboratory at IRMM. These targets have been characterized for both their total mass and mass distribution over the sample area.

238U Neutron Capture Cross Section Measurements at the GELINA Facility

A set of neutron capture experiments based on the time-of-flight technique were performed in order to determine the 238U capture cross section in the unresolved resonance region. The GELINA facility of the Institute for Reference Materials and Measurements (IRMM) served as the neutron source. A pair of C6D6 liquid scintillators was used to register the prompt gamma rays emerging from the uranium sample. The analysis of the experimental data is based on the total energy principle applied in combination with the pulse height weighting technique. The experimental details along with the analysis process are described. The first results in the resolved resonance region are presented and their validity provide a solid base to extend the analysis and extract the average cross section in the keV region.

Eurachem’s 25th anniversary: two members’ perspective

Eurachem was founded 25 years ago. Its prime aim, as wasset out in the Memorandum of Understanding (MoU)signed by its members, was to help establish a system ofinternational traceability for chemical analysis. At thattime, there was little international activity in this topic or inthe broader field that could be classified as Metrology inChemistry (MiC); in fact, the concept ‘‘Metrology inChemistry’’ was hardly in use. The ‘‘Guide to the Expres-sion of Uncertainty in Measurement’’ (GUM) [1] had not yetbeen published, but there had been a lot of activities on theevaluation of uncertainty in the higher echelons of physicalmeasurements following the publication of recommenda-tions of the International Bureau of Weights and Measures(BIPM) working party on ‘‘Expression of MeasurementUncertainties’’ in 1980. This way of evaluating andreporting uncertainty had also percolated to other areas ofphysical measurement but had attracted little or no attentionfrom analytical chemists. As a matter of fact, the Interna-tional Committee for Weights and Measures (CIPM) onlystarted to take interest in chemical measurement in the lateeighties.The GUM was published in 1993 based on these BIPMrecommendations, and it is such an important landmark inthe development of metrology that it is worth repeating itsbasic principles and the changes these engendered. Previ-ously, most of the discussion and reporting of accuracy hadbeen based on the concept of a ‘‘true value’’ and randomand systematic errors. Since the true value is unknown andunknowable, and systematic errors are difficult if notimpossible to evaluate, accuracy statements were mainlybased on measurement repeatability or in some casesreproducibility. GUM changed all that, as is stated in theintroduction to Annex D, ‘‘the concept of uncertaintyadopted in this guide is based on the measurement resultand its evaluated uncertainty rather than the unknowablequantities ‘‘true’’ value and error.’’GUM found fairly rapid adoption for physical mea-surements. However, it had received very little attention inchemical measurements before the publication in 1995 ofthe guide ‘‘Quantifying uncertainty in analytical measure-ment’’ by Eurachem and CITAC (Cooperation onInternational Traceability in Analytical Chemistry), afterwhich, together with pressure from the accreditation bod-ies, uncertainty evaluation became common practice as isexemplified by its use in a large number of articles in thisjournal.It is strange that uncertainty evaluation was the first stepin applying MiC principles, rather than establishment oftraceability of measurement results, particularly since it isthe latter that was a primary aim of Eurachem. A workshopon ‘‘Traceability and Comparability’’ was held at theCentral Bureau for Nuclear Measurements (CBNM, laterthe Institute for Reference Materials and Measurements(IRMM)) in November 1992, but it was a number of years,with much discussion and many papers [2] before the firstreal concepts started to be developed on how to establishtraceability, and the Eurachem/CITAC Guide ‘‘Traceabilityin chemical measurement’’ was not published until 2003.The solution turned out to be very similar to that forphysical measurements, i.e. establishment of traceabilityfor all of the measured values of quantities that are in the

Setting maximum limits for trace elements in baby food in European legislation: the outcome of International Measurement Evaluation Programme®–33

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate-General of the European Commission, operates the International Measurement Evaluation Programme® (IMEP). It organises various types of inter-laboratory comparisons in support of European Union policies. This paper presents the results of a proficiency testing exercise (PT) focusing on the determination of total cadmium (Cd) and total lead (Pb) mass fractions in baby food in support to Commission Regulation (EC) 1881/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs. The test material used in this exercise was soya-based baby food formula purchased in a local pharmacy and prepared by the Reference Materials Unit of the IRMM for this exercise. Sixty-six laboratories from 23 countries registered to the exercise and 61 of them reported results. Each participant received one bottle containing approximately 15 g of test material. Participants were asked to quantify the measurands in the powder and in the reconstituted formula. Reference values independent from the participants’ results were established using isotope dilution inductively coupled plasma mass spectrometry. The total Cd mass fraction was determined by IRMM and LGC Ltd (UK), while the total Pb was determined by IRMM. The standard deviation for proficiency assessment was set at 22% of the assigned value for all measurands. Laboratories were rated with z- and ζ- (zeta) scores in accordance with ISO 13528. The outcome of this exercise is clearly influenced by the very low level of Cd and Pb content in the test material which triggered: a high number of ‘less than’ values; overestimated values especially for Pb very likely due to contamination; and a visible method influence in the case of Pb (methods based on atomic absorption were not sensitive enough to attain such low limits of detection). The results were also evaluated with regard to the reported limit of detection and some incoherencies were observed.