Determination of the standard deviation for proficiency assessment from past participant’s performances

The “uncertainty function” introduced by Thompson et al. estimates the reproducibility standard deviation (SR) as a function of concentration. This model was successfully applied to a data set derived from three proficiency testing schemes aiming at the quantification of three toxic elements (cadmium, lead and mercury) in blood and urine. A threshold concentration was determined for each element. Below this concentration SR is found to be constant, while above it the reproducibility relative standard deviation is constant. This model allows the a priori estimation of standard deviation for performance assessment for proficiency testing rounds.JRC.D.5-Standards for Food Bioscienc

Determination of the standard deviation for proficiency assessment from past participant's performances

The "uncertainty function" introduced by Thompson et al. estimates the reproducibility standard deviation as a function of concentration or mass fraction. This model was successfully applied to data derived from three proficiency testing schemes aiming at the quantification of cadmium, lead and mercury in blood and urine. This model allows the estimation of standard deviation for the performance assessment for proficiency testing rounds

Guidance Document on the Estimation of LOD and LOQ for Measurements in the Field of Contaminants in Feed and Food

The European Union Reference Laboratory (EURL) for Polycyclic Aromatic Hydrocarbons (EURL PAH), the EURL for Heavy Metals in Feed and Food (EURL HM), the EURL for Mycotoxins (EURL Mycotoxins), and EURL for Dioxins and PCBs in Feed and Food aim to provide with this document guidance to official food control in the EU on the estimation of the limit of quantification of analytical methods for the determination of individual substances in the field of contaminants in feed and food. The document focusses on estimation of the limit of detection (LOD) and/or limit of quantification (LOQ) of polycyclic aromatic hydrocarbons (PAHs), heavy metals (HM), mycotoxins, and polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs). The concept presented here consists of two major routes: The first route responds to the requirements for determination of PAHs, HMs and Mycotoxins. The second route corresponds to PCDD/F and PCB analysis, where results are calculated as sum-parameters and expressed in toxic equivalents (TEQs), converting thereby congener concentrations together with estimated LOQs using toxic equivalency factor (TEFs) into TEQs. Due to the nature of this more complex procedure, emphasis is put in the area of PCDD/F and PCB analysis on the LOQs, while LODs are of minor consequence. Terminology in this guidance document was adapted to the chemical analysis of contaminants in feed and food; hence, some of the general terms defined and used in international standards were replaced by more specific terms applicable to analytical chemistry. The presented statistical-mathematical approach is based on elements taken mainly from DIN 32645:2008-11 (DIN 2008) and ISO 11843-2:2000 (ISO 2000). This document covers only quantitative methods of analysis. The authors believe that LOD and LOQ values derived from the application of the presented experimental methodologies converge to a certain degree. Estimation of LOD/LOQ values based on blank measurements, and from calibration data is described. Signal-to-noise ratios are applied in the area of PCDD/Fs and PCBs. Mathematical terms and statistical background are presented as well. This guide document shall be applied systematically if measurement results are used for monitoring purposes and exposure modelling. However, authors are aware that precise knowledge of LOD/LOQ may not be required when assessing compliance with maximum levels exceeding LOD/LOQ. This guidance document shall be applied if maximum levels and analysis results are close to the expected LOQ.JRC.F.5-Food and Feed Complianc

Report of the Ninth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-109: Total Cadmium, Lead, Arsenic and Mercury as well as Methylmercury and Inorganic Arsenic in Seafood

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the ninth proficiency test (PT) of the EU-RL-HM which focused on the determination of total cadmium, lead, arsenic and mercury as well as methylmercury and inorganic arsenic in seafood. The test material used in this exercise was the Certified Reference Material (CRM) DOLT-4, dogfish liver of the National Research Council of Canada (CNRC). The material was relabelled to prevent recognition by the participants and was dispatched the second half of May 2010. Each participant received one bottle containing approximately 20 g of test material. Thirty-eight laboratories from 27 countries registered to the exercise of which 38 reported results for total Cd, 36 for total Pb, 33 for total As, 36 for total Hg, five for methylmercury and 10 for iAs. The assigned values for total Cd, Pb, As, Hg and methylmercury are the certified values taken from the DOLT-4 certificate. An attempt was made to establish an assigned value for inorganic As (iAs) using the results provided by a group of five laboratories expert in the field, following a similar approach to that used in IMEP-1071, a PT on total and inorganic arsenic in rice. Contrary to what was observed in IMEP-107, the results obtained by the expert laboratories for iAs was method dependent, therefore no assigned value could be established. The uncertainties of the assigned values, uref, were taken directly from the CRM certificate as provided by the producer for total Cd, Pb, As, Hg and methylmercury. Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise. Laboratory results were rated with z- and ¿-scores (zeta-scores) in accordance with ISO 135282. Since the concentration of iAs seems to be method dependent according to the results obtained by the expert laboratories, no scoring was provided to the laboratories that submitted results for iAs. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15% by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EURL-HM and on the state-of-the-art in this field of analysis. Between 80 and 97.5 % of the laboratories performed satisfactory for total Cd, As, Hg and methylmercury. Regarding total Pb, 70 % of the laboratories scored satisfactory.JRC.DG.D.6-Food Safety and Qualit

IMEP-30: Total Arsenic, Cadmium, Lead, and Mercury, as well as Methylmercury and Inorganic Arsenic in Seafood - Interlaboratory Comparison Report

This report presents the results of an ILC which focussed on the determination of total As, Cd, Pb , and Hg, as well as methylmercury and inorganic arsenic in seafood. The test material used in this exercise was the Certified Reference Material (CRM) DOLT-4, dogfish liver of the National Research Council of Canada (NRC). Each participant received one bottle containing approximately 20 g of test material. Fifty-seven laboratories from 29 countries registered to the exercise and all of them reported results. The assigned values and their associate uncertainties for total As, Cd, Pb, Hg and Methylmercury are the certified values taken from the DOLT-4 certificate. An attempt was made to establish an assigned value for inorganic As (iAs) using the results provided by a group of five laboratories expert in the field. Unfortunately, contrary to what was expected, the results obtained by the expert laboratories for iAs showed a large spread and no assigned value could be established.JRC.DG.D.6-Food Safety and Qualit

Guidance document on Measurement Uncertainty for GMO Testing Laboratories 3rd Edition

This document provides guidance to GMO control laboratories on how to estimate measurement uncertainty (MU) associated with any GMO measurement result. Competent authorities have a responsibility to decide if a measurement result exceeds the legal threshold. Consequently control laboratories must estimate and report the MU of their measurement results. Quantitative polymerase chain reaction (qPCR) and digital polymerase chain reaction (dPCR) are the methods applied for the enforcement of EU law on GMO labelling. This document takes into account: current EU legislation, the availability of certified reference materials (CRMs) and validated methods, and the need for control laboratories which conduct measurements for the enforcement of EU legislation to be accredited according to ISO/IEC 17025. Based on these, two approaches for the estimation of MU for PCR measurement results are presented in this guidance document. References to alternative approaches are also provided.JRC.F.5-Food and Feed Complianc

IMEP-26: Determination of Brominated Flame Retardants in Plastic

This report presents the results of an interlaboratory comparison (ILC) which focussed on the determination of total bromine, total sum of polybrominated biphenyls (PBB), total sum of polybrominated diphenylethers (PBDE), brominated diphenylethers (BDE-47, BDE-99, BDE-183 and BDE-209) and decabrominated biphenyl (BB-209) in plastic. The test material used in this exercise was the Quality Control material (IRMM-310) from the Institute for Reference Materials and Measurements (IRMM) a poly(ethyleneterephthalate) (PET) granulated that has been fortified with commercially available technical mixtures of polybrominated diphenylethers and polybrominated biphenyls. The material was relabelled to avoid its recognition. Twenty-five laboratories from 15 countries registered to the exercise, from which 23 reported results. The informative values provided by the IRMM-310 material information sheet were taken as the assigned values and their associated uncertainties for all measurands. Studies to asses the adequacy of the selected test material regarding its homogeneity for all the selected measurands were undertaken Participants were invited to report the uncertainty of their measurements. Laboratory results were rated with z- and ζ-scores (zeta-scores) in accordance with ISO 13528. The standard deviation for proficiency assessment was fixed to 25 % of the respective assigned value by the advisory board of this ILC. The outcome of the exercise was illustrating quite well the difficulties laboratories do have to provide consistent values for the investigated measurands; the share of satisfactory z-scores ranged between 61 and 88 %. There was a clear tendency to underestimate most of the measurands. The most influencing variables, leading to the observed variability and lack of trueness, were investigated.JRC.DG.D.6-Food Safety and Qualit

EURL-FA Control Proficiency Test Report: Determination of the mass fraction of the total cobalt in compound feed for rabbits

The European Union Reference Laboratory for Feed Additive Control (EURL-FA Control) organised a proficiency test (EURL-FAC 2017-2) for the determination of the mass fraction of total cobalt in compound feed, to support the Commission Implementing Regulation (EU) No 131/2014 concerning the authorisation of various cobalt(II) compounds as feed additives. This proficiency test was open to National Reference Laboratories (NRLs) and official feed control laboratories (OCLs). The material used as test item was a commercially available compound feed for rabbits (containing the coated granulated cobalt (II) carbonate, 3b304 ) which, after appropriate processing, was bottled, labelled and dispatched to participants on June 21, 2017. The homogeneity and stability of the test item were evaluated and the assigned values were derived from the results reported by the selected expert laboratories. Twenty one NRLs and two OCLs from 21 countries - representing EU Member States and Norway - registered to the exercise and reported results at the end of August 2017. Laboratory results were rated using z' and zeta scores in accordance with ISO 13528:2015. A relative standard deviation for proficiency assessment (σpt) of 16 % of the assigned value was set according to the modified Horwitz equation. Twenty (out of 23) laboratories reported satisfactory results (according to the z' score). This confirms the ability of most NRLs in monitoring maximum levels set by the Commission Implementing Regulation (EU) No 131/2014 in this type of animal feed. The majority (74 %) of the participating laboratories provided realistic estimates of their measurement uncertainties.JRC.F.5-Food and Feed Complianc

Report of the Tenth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-110: Total Arsenic, Cadmium, Mercury and Lead in Vegetable Food

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) a Directorate-General of the European Commission operates the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the tenth ILC of the EU-RL-HM which focused on the determination of total arsenic, cadmium, mercury and lead in vegetable food. The test material used in this exercise was the Standard Reference Material SRM 1570a, spinach leaves of the National Institute of Standards and Technology (NIST). The material was rebottled and relabelled to prevent recognition by the participants and was dispatched at the beginning of June. Each participant received one bottle containing approximately 15 g of test material. Thirty-five laboratories from 24 countries registered to the exercise of which 35 reported results for total Cd and total Pb, 32 for total As and 31 for total Hg. The assigned values for total As, Cd and Hg are the certified values taken from the SRM 1570a certificate. For total Pb, the "information value" provided by NIST in the SRM certificate was used as assigned value. The uncertainties of the assigned values (uref) for total As, Cd and Hg, were taken directly from the CRM certificate as provided by the producer. No uref is provided by NIST for the total Pb concentration because the total Pb content is only provided as "information value". Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise. Laboratories' results were rated with z- and zeta-scores for total As, Cd, and Hg in accordance to ISO 13528. No zeta-scores were given for total Pb because uref was not known for that measurand. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15 % for all the measurands by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EU-RL-HM and on the state-of-the-art in this field of analysis. More than 80 % of the participants performed satisfactory for total Cd and Hg. Around 70 % of the participants obtained a satisfactory z-score for total arsenic with a relatively high number (8 laboratories) of participants having overestimated the total content of arsenic in the test material. When looking at the zeta-scores, 60 to 65 % of the reported results were satisfactory when the associated uncertainties are taken into account.JRC.DG.D.6-Food Safety and Qualit

Report of the Second Interlaboratory Comparison Organised by the Community Reference Laboratory for Heavy Metals in Feed and Food: Total Cd, Pb and Hg in Mineral Water

The Institute for Reference Materials and Measurements (IRMM) of the European Commission's Directorate-General Joint Research Centre holds the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM). One of the core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the second ILC of the CRL-HM which focused on the determination of the total Cd, Pb and Hg content in mineral water. The test material used in this exercise was a commercial mineral water purchased in Belgium at a local supermarket. The material was spiked with Cd, Pb and Hg, rebottled and dispatched by the Reference Material Unit of the IRMM. The samples were dispatched on the first half of May 2007. Each participant received two sets of samples containing one bottle per set. Each bottle contained approximately 100 mL of test material. Twenty participants from 17 countries registered to the exercise of which 20 submitted results for Cd and Pb and 19 for Hg. The assigned values were those obtained from the gravimetric measurements used to spike the material. The homogeneity and stability studies were subcontracted to the University of Natural Resources and Applied Life Sciences (BOKU) in Vienna. The uncertainty of the assigned values was calculated combining the uncertainty of the spiking procedure with a contribution for the between-bottle homogeneity and for long-term stability of the test material. Participants were invited to report the uncertainty on their measurements. This was done by all them. Laboratory results were rated with z and zeta scores in accordance with ISO 135281. Standard deviation for proficiency assessment (also called target standard deviation) for Cd, Pb and Hg was 10% of the assigned value.JRC.D.4-Isotope measurement