The importance of laboratory performance evaluation in qualitative and interpretative proficiency testing (PT) and external quality assessments (EQA) has increased significantly over recent years. Unfortunately, the relevant ISO standards provide limited guidance on how these assessments could be harmonised. In 2014, the Eurachem PT Working Group performed an initial survey on current practices applied by PT/EQA providers in these areas. This paper presents the results of this survey along with the findings of an extensive literature review on the subject extended to 2020. Both the survey results and the literature search show that, even though a majority of scoring systems are based on simple yes/no or absence/presence responses, multiple types of performance evaluation criteria are in use for qualitative and interpretative PT/EQA schemes. This represents a clear disadvantage compared to the more aligned approach in quantitative PT/EQA schemes since laboratory proficiency between schemes is not as easily comparable. The paper presents current practices and scoring systems grouped by categories with defined criteria and may serve as a basis for further discussion and investigation towards the harmonisation of performance evaluation in qualitative and interpretative PT/EQA schemes.

Quality and reliability of analytical results are, in general, key issues for all laboratories but become a top priority for laboratories accredited according to ISO/IEC 17025:2005. In this international standard the proficiency testing (PT) is regarded as a means to assure the validity of results. Nowadays, the proved competence of laboratories is an essential requirement especially for that structures that are involved in the official controls aimed at ensuring the safety of EU food products and the public health. To guarantee the EU consumers, the Council and the Commission have designated 28 European Union Reference Laboratories (EURLs) for food and feed, whose main role is to contribute to the standardization of analytical methods and to the harmonization of performance among the EU National Reference Laboratories (NRLs) to reach a comparable level of quality in the analytical data among all Member States. With this aim, the organization of PTs is a task that each EURL has to accomplish. Over the last 15 years, the EURL for chemical elements in food of animal origin (EURL-CEFAO) have organized 32 PTs on determination of total As, Cd, Pb and total Hg in meat, milk, fish and offal for the benefit of its network of NRLs. Some specific aspects of this activity will be discussed (e.g. preparation and characterization of PT materials, statistical evaluation of data, follow-up actions). Finally, based on the EURL-CEFAO experience, it will be demonstrated that the participation into PTs on a regular basis can result in an improvement of the laboratory's performance as well as in the harmonization of the results submitted by participants.

A pilot study was carried out to evaluate the transfer of As, Cd, Pb, Ni, Cr and Hg from milk to dairy products and to correlate their behavior with that of some components and macro-elements of milk. Due to the low level of these chemical elements in most common commercial products, hard cheese was produced starting from cow's milk spiked with the analytes of interest. Several intermediate and final products coming from cheese making were sampled and analysed for content of fat, dry matter, proteins, macro and oligo-elements. The relationship between spiked elements and milk components was evaluated through both the study of concentration factors and the statistical analysis (Principal Component Analysis and correlation matrix). Except for As and Hg, a clear correlation between spiked elements and milk components was found so a likely bond with proteins, fat and dry matter was demonstrated. As for Pb, for which a legal limit (Maximum Level, ML) is set in the pertinent European regulations, it was found that the link with proteins could lead to an increase of this element concentration different from the mere concentration factor from milk to cheese. Furthermore, it was proven that the stage of ripening affected the variation of Pb concentration so this aspect should be deeply considered in case of setting a ML in cheese or extrapolating a ML from milk to cheese.

A summary of the working group discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Berlin, Germany, 6–9 October 2014 is provided. The working groups covered a range of issues concerned with current practice and future directions: review of ISO/IEC 17043; user perspective of PT/EQA; sampling PT/EQA; the revised ISO 13528; PT/EQA in developing countries; and harmonisation of performance assessment in qualitative PT/EQA. Delegates from 64 countries attended the workshop, and this diversity of different backgrounds was represented on each of the working groups in order to capture a range of views and experience from a number of different measurement sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes, end-users of PT/EQA results such as accreditation bodies and regulatory authorities, national measurement institutes, laboratory associations, universities and independent consultants from countries around the world.

One of the emerging issues regarding the analysis of inorganic contaminants in food is the determination of Cadmium (Cd) and Lead (Pb) in honey. In fact, this kind of analysis is foreseen in most of the National Residue Control Plans (NRCPs) that European Union Member States (EU MSs) have to perform according to Directive 96/23. With the aim to provide technical support to the EU National Reference Laboratories (NRLs), an easy-to-use method on direct determination (DD) of Cd and Pb in honey by graphite furnace atomic absorption spectrometry (GF-AAS) after dissolution in an aqueous mixture of 2.5 % HNO3 (v/v) and 12.5 % H2O2 (v/v) was in-house validated and distributed to the NRLs network. Analyses were carried out on a batch prepared for the feasibility study of the EURL-CEFAO 19th PT on honey. The validation levels (20 and 100 µg/kg for Cd and Pb, respectively) were chosen similar to those that would have been proposed for the PT. The method proved its efficacy in terms of analytical performance; it appears to be low cost and time saving compared to a microwave sample preparation. In addition, it also decreases the environmental impact, being the amount of acid and reagents considerably reduced.

The European Union Reference Laboratory for Chemical Elements in Food of Animal Origin (EURL-CEFAO) is a proficiency testing (PT) provider accredited according to ISO Guide 43-1 and later to ISO/IEC 17043:2010. It organizes exercises devoted to expert laboratories of the EU Member States. PTs are proposed taking into account matrices, analytes, maximum levels (MLs) ruled in Commission Regulation (EC) 1881/2006 (and following amendments) and discussions about new or modified MLs. Following this approach, an exercise was organized in 2012 on the measurement of the cadmium (Cd) and lead (Pb) mass fraction in powdered infant formula based on animal proteins (17th PT). One of the goals was to prepare a material containing Cd around the probable new ML so as to allow participants to test their performance at such a level. The procedure to produce the PT material was set on the basis of the EURL long experience in preparing freeze-dried samples and was tested on a preliminary batch. Homogeneity and stability of the PT material were evaluated through procedures based on international standards. For all tests, a standard deviation for proficiency assessment (σ pt), more restrictive than that from the Horwitz equation (σ H), was used. The mass fraction of Cd and Pb in the material was proven to be homogeneous and stable for 15 months. These results are extremely satisfactory taking into account the low mass fraction proposed and the restrictive standard deviation for proficiency assessment used to perform the tests. Furthermore, the PT was particularly useful considering that Commission Regulation (EC) 1881/2006 has been recently amended [CR (EU) 488/2014] with the introduction of the new ML for Cd in infant formulas consistent with the mass fraction value proposed in the 17th PT.

Honey is widely analysed by many European Union control laboratories for heavy metals in foodstuffs. No maximum levels are set for cadmium and lead in this matrix, but most of the member states include this analytes–matrix combination in their National Residue Monitoring Plans setting specific action levels. The need to harmonize these values is under consideration within the European Commission. The lack of suitable certified reference materials as well as the scarcity of appropriate proficiency testings imply a difficulty for the official and National Reference Laboratories in the assessment of their method performance. The European Union Reference Laboratory for Chemical Elements in Food of Animal Origin organized the 19th PT on the determination of cadmium and lead in honey giving its network the possibility of checking the performances of the analytical methods used. An adequate procedure for the preparation of honey material spiked with cadmium and lead at values of mass fraction of interest (roughly 20 and 100 µg kg−1 for cadmium and lead, respectively) was developed. A commercial wildflower honey was spiked at proper concentration levels, achieving suitable fluidity and homogeneity by mild heating and stirring. Homogeneity and stability were investigated using an ad hoc validated analytical method and the PT material was found homogeneous and stable, covering the time span of the interlaboratory comparison. These outcomes as well as the good agreement between the assigned values and the values obtained from the homogeneity test confirmed the effectiveness of the procedure for the production of the material and the fitness of the material for the purpose of this PT.

One of the tasks of European Union Reference Laboratories (EURLs) for feed and food is the organization of proficiency testing (PTs) for the network of National Reference Laboratories (NRLs) of EU member states according to the area of competence. This crucial assignment leads the EURL for Chemical Elements in Food of Animal Origin (EURL-CEFAO) to plan PTs that include various chemical element/matrix/concentration combinations in order to organize a profitable exercise for its network. The purpose of this paper was to describe the "step-by-step" preparation of a PT material and the efforts of an EURL to provide proper test items to national laboratories (NRLs). The exercise was tailored to train participants and give them the opportunity to practice around the maximum levels (MLs) set in EU legislation, values at which sample acceptance is the critical issue. The EURL strategy has been chosen considering the role of the NRLs that could be summoned as third party in legal controversies. A PT on the determination of cadmium and lead in freeze-dried liver was then scheduled. The goal was to achieve a sample with a mass fraction (w) of the elements around the ML (0.50 mg/kg for both). Preliminary studies allowed the EURL to calculate the amount of spike to reach the target mass fractions. The target Cd and Pb mass fractions were in good agreement with the contents found in the frame of the homogeneity test as well as with the consensus values derived from the results reported by the PT participants. This proved the suitability of the production procedures and the quality of the delivered PT test items.

Cadmium (Cd), lead (Pb) and arsenic (As) can enter the food chain through the environment and/or as a consequence of the manufacturing process making foodstuffs the main human exposure route to these chemical elements. The risk associated with this exposure is of such a big concern for human health that the European Food Safety Agency recommends to reduce the exposure to Cd and Pb so as to protect especially vulnerable subgroups of population (e.g., infants). Therefore, the setting of new maximum levels (MLs) for chemical elements in infant formulae (e.g., for Cd) or the reconsideration of the existing ML for Pb is under discussion. On this basis, the availability of analytical methods, precise, accurate and sensitive enough to quantify low concentration values, is a key point especially for official control laboratories that have to state the sample compliance using a fully validated method with an associated uncertainty compliant with the requirements specified in the pertinent regulations. This work describes the development and validation of an analytical method to quantify As, Cd and Pb in powdered infant formulae based on animal protein at values of concentration close to the MLs that are likely to be set. The results obtained make the method suitable for a precise and accurate determination of these chemical elements at these low concentration values. In particular, the results for limit of quantification (LoQ) were respectively (μg kg−1): As 6.2, Cd 1.2 and Pb 4.5. While for the recovery rates the following percentages were obtained: As 105%, Cd 98% and Pb 108%. The expanded uncertainties were found extremely satisfactory (Cd 13% and Pb 19%). The LoQ and the uncertainty for Pb meet the requirements set in Commission Regulation (EC) No. 333/2007 and following amendments being lower than the maximum values allowed. Even for Cd the expanded uncertainty resulted adequate in relation with the low concentration considered.

Laboratories dealing with the analysis of food of animal origin have to face the shortage of both appropriate certified reference materials and pertinent proficiency tests (PTs). Therefore, internal quality control (IQC) materials have to be prepared in-house. The combination matrix/analytes/concentration, as well as the physical state, is a key issue. The European Union Reference Laboratory for Chemical Elements in Food of Animal Origin (EURL-CEFAO), within its activity as PT provider, has set a procedure to prepare test items of liquid milk spiked with arsenic, cadmium and lead at adequate values of concentration. This work describes in detail the steps of this procedure. Homogeneity and stability of the PT test items thus prepared were evaluated by the EURL-CEFAO using a sensitive and accurate method accredited according to ISO/IEC 17025. The analyte concentrations in spiked milk were found stable up to 18 months which is of particular interest for cadmium due to the low value of spiking (roughly 5 μg/kg). The outcome proves that the procedure used to prepare liquid milk spiked with chemical elements is suitable to produce in-house reference materials stable enough for analytical purposes. Furthermore, this procedure is easy to perform and can be applied by routine laboratories to produce samples for their IQC.

As proficiency tests (PTs) provider, the European Union Reference Laboratory for Chemical Elements in Food of Animal Origin (EURL-CEFAO) yearly organizes exercises on the determination of chemical elements within the area of its mandate. The scheme is addressed to the National Reference Laboratories (NRLs) of the European Union Member States. Each PT is planned giving priority to the matrices and elements for which maximum levels are set in Commission Regulation No. 1881/2006 and following amendments as well as to those mainly considered in National Residues Control Plans. Samples to be distributed are prepared in the Laboratory’s facilities using materials purchased on the market and often adjusting the concentration levels of the analytes around their maximum levels. In the 2006–2011 period, PTs were planned as a long-term programme pursuing the general objective of providing the NRLs with a scheme that can give them the opportunity to check and improve the performance of their analytical methods and to verify the effectiveness of any corrective actions through the repetition of the same matrix. Control charts give participants the possibility of a long-term follow-up of their performance promoting the improvement of Quality Control. To this aim, Shewhart and Cusum control charts for z-scores are prepared according to ISO 13528:2005 and updated after each PT for each laboratory. z-scores are assigned using values of σ pEURL-CEFAO that correspond to the level of performance appropriate to the demand. Cusum charts are also evaluated by EURL-CEFAO in order to identify problems that may cause a bias in the measurement method.

The widespread use of herbal drugs, among which those coming from eastern Countries, has created a more compelling need for quality, a pre-requisite that can influence safety.In the present study, 10 Chinese crude herbal drugs marketed in Italy (Radix Ginseng, Radix Astragali, Rhizoma Coptidis, Rhizoma Atractylodis Macrocephalae, Radix Bupleuri, Radix Rehmanniae, Radix Paeoniae Alba, Pericarpium Citri Reticulatae, Radix Polygalae, Radix Salviae Miltiorrhizae) were analysed by the following purity assays: foreign matter, total ash, microbial and heavy metal contamination.Each herbal drug was purchased in Italy from three different sources: two Chinese firms and one Chinese herbal shop. Except for the heavy metal content, the tests were performed according to the European Pharmacopoeia.The presence of parasites was shown in two samples; moreover, level of ash (in three samples), lead content (in one sample) and total viable aerobic count (in one sample), were higher than the limits set by the European or Italian Pharmacopoeias.Our results, even if obtained from a small number of herbal drugs, show some purity issues and underline the importance of the quality control, particularly for this kind of products whose therapeutic value is not always demonstrated.

A proficiency test on the quantification of Al, Cu, Mn, Se and Zn in serum was carried out to verify the performance of about 30 regional laboratories of the network of Italian laboratories. The exercise consisted of four runs in which the laboratories were free in choosing analytical methods to determine trace elements in freeze-dried animal serum. Laboratories performances were evaluated by the study of statistical functions as Coefficients of Variation (CV), Youden plot and Z-score value. As for Al, the results were generally characterized by good accuracy and precision, in spite of the low levels of the element (5-7 microg l(-1)). Copper determination had some problems only at low concentration (about 160 microg l(-1)--first run), in which an elevated number of anomalous data were found. Better data were achieved for Zn, for which anomalous values were mainly stragglers than outliers. Due to the low number of data for Mn (concentrations from 0.6 to 60 microg l(-1)) and Se (concentration from 45 to 106 microg l(-1)), a restricted statistical treatment was applied; for these elements high CV values were found (range from 30 to 80%). The results of this trial confirmed that participation in a proficiency test represents a benefit for all analytical laboratories. In fact, with few exceptions, most of the participants improved their performances in terms of Z-score values.

We evaluated the presence of Ca, Na, K, Cu and Zn in the lenses and aqueous humour of rabbits treated with an Nd:YAG laser to induce opacity of the crystalline. The mean concentrations of the elements found in control lenses were: Ca: 15.8±5.2mg/kg; Na: 1.2±0.6g/kg; K: 10.3±3.3g/kg; Cu: 0.19±0.06mg/kg; Zn: 20.6±3.0mg/kg. With the exception of K and Zn, the values found in the lenses of treated eyes (Ca: 135±24mg/kg; Na: 4.3±1.5g/kg; K: 10.1±3.2g/kg; Cu: 0.47±0.17mg/kg; Zn: 21.8±4.2mg/kg) were significantly higher than in the controls. On the other hand, the concentrations found in the aqueous humour of treated eyes (Ca: 21.7±4.5mg/l; Na: 0.66±0.21g/l; K: 0.29±0.10g/l; Cu: 0.035±0.009mg/l; Zn: 0.079±0.01mg/l) were significantly lower than those of the controls. The greatest difference was observed for Na (−68.6%) and Cu (−52.7%), followed by Ca and Zn (−35.0% and −35.2%, respectively). A positive correlation was found between Ca and Na in treated lenses (r2=0.9226, p<0.0001) whereas inverse correlations were found for both Ca (r2=0.9788, p<0.0001) and Na (r2=0.9491, p<0.0001) between the concentrations found in the lenses and in the aqueous humour of treated eyes.

Concentrations of cadmium, chromium, lead and vanadium were determined in samples of six fish species collected along the coast of the Adriatic Sea. The concentrations of the elements studied were generally low, often below the detection limits of the analytical methods. The highest values (microg x kg(-1) fresh weight) were observed, mainly in the central area of the Adriatic Sea, for anchovy (Cd 20.2, Cr 82.9, Pb 45.9, V 89.9), red mullet (Cd 3.1, Cr 31.0, Pb 36.0, V 79.1) and mackerel (Cd 7.7, Cr 28.0, Pb 11.4, V 43.5). The concentrations of cadmium and lead in all the species examined were below the maximum levels indicated by the European Community for these two elements in seafood, and also would lead to exposure levels lower than the provisional tolerable daily intakes suggested by the FAO/WHO for Cd (420 microg x week(-1) for a 60-kg person) and Pb (1500 microg x week(-1) for a 60-kg person). The concentration of chromium was lower than the recommended daily amount (50-200 microg x day(-1) for a 60-kg person) indicated by the US National Research Council. An 11-34% contribution to the daily vanadium ingestion with fish was calculated for the population of the Adriatic coast.

The determination of inorganic ions in cataractous human lenses has been the subject of several investigations; nevertheless, few studies have been concerned with trace element contents in lenses, and data are sometimes contradictory. An animal experimental model of induced cataract is here proposed with the aim of evaluating the changes of Ca, Na, K, Cu and Zn concentrations. The cataract was produced by an Nd:YAG Laser treatment of the right eye of sexteen male rabbits. The determination of the elements was performed by atomic absorption spectrometry (both flame and flameless methods) after an acid digestion of samples. Compared with the results obtained in left lenses used as a control (Ca 14.4+/-5.7 mg/kg d.w.; Na 1.3+/-0.5 g/kg d.w.; K 9.9+/-1.1 g/kg d.w.; Cu 0.24+/-0.09 mg/kg d.w.; Zn 24.8+/-2.3 mg/kg d.w.), the mean concentration values of opaque lenses showed some significant changes for Ca, Na, and Cu (Ca 123.7+/-106.6 mg/kg d.w.; Na 4.5+/-4.3 g/kg d.w; Cu 0.43+/-0.21 mg/kg d.w.). Potassium showed a tendency to decrease, and zinc to increase. Positive correlations were found between calcium and sodium both in controls (r=0.73, p<0.001) and in treated lenses (r= 0.87, p<0.0001). An inverse correlation between Ca and K confirmed the tendency of potassium to decrease.

Samples of chocolate, cocoa, tea infusions, soft drinks and fruit juice have been examined by electrothermal atomic absorption spectrometry (ETA-AAS) for the presence of aluminium (Al). Fruit juices and chocolate were analysed after an adequate sample preparation; the other products were evaluated directly. Sampling was performed in duplicate for 248 independent samples. The mean Al concentration in chocolate was 9:2 ± 7:5 mg kg1, and individual values were correlated with the per cent of cocoa in samples (Y = 0:63 + 0:27X, r = 0:78, p < 0:0001). Al concentration in commercial tea infusions ranged from 0.9 to 3.3 mg l-1 (X = 1:80 ± 65 mg l-1), whereas in laboratory-prepared samples it was 2:7 ± 0:93mg l-1. In soft drinks, the concentrations of Al were lower, ranging from 9.1 to 179 μgl-1; the highest values were observed in samples of orange squash (X = 114 ± 56 μg l-1). Apricot juice showed the highest Al level (X = 602 ± 190 μgl-1), being statistically diOEerent from that of pear (X = 259 ± 102 μgl-1), but not diOEerent from that of peach juice (X = 486 ± 269 μgkg-1). Toxicologically, the amount of Al deriving from the consumption of these products is far below the acceptable daily intake of 1mg kg-1 body weight indicated by the FAO/WHO, and it is a very low percentage of the normal Al dietary intake.

The concentrations of trace metals (Be, Bi, Cd, Cr, Mn, Ni, Pb, Sn, Zn), aluminium, iron and total organic carbon (TOC) were determined in sediments collected in Antarctica (Terra Nova Bay-Ross Sea). Samples were analysed by atomic absorption spectrometry with either flame or flameless techniques. Chemical data were evaluated taking into account the textural and compositional character of the sediments. The mean concentration levels of the elements in the < 2 mm granulometric fraction were (mg/kg): Be: 2.04 +/- 0.25; Bi less than or equal to 0.8; Cd: 0.26 +/- 0.16; Cr: 20.3 +/- 8.3; Mn: 359 +/- 108; Ni: 6.31 +/- 3.5; Pb: 20.7 +/- 2.8; Sn: 2.12 +/- 0.71; Zn: 42.3 +/- 10.4; Al: 56100 +/- 3900; Fe: 16400 +/- 4800. The mean value of TOC was 0.34 +/- 0.20 g%. In the < 63 mu m fraction higher levels were observed for all the elements, with the exception of Al and Be. Both petrographic and chemical analyses showed differences between the samples collected in Terra Nova Bay and the sample from Wood Bay. (C) 1999 Published by Elsevier Science B.V. All rights reserved.