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The availability of a suitable matrix reference material is essential for standardization of the immunoassays used to measure serum proteins. The earlier serum protein reference material ERM-DA470 (previously called CRM470), certified in 1993, has led to a high degree of harmonization of the measurement results. A new serum protein material has now been prepared and its suitability in term of homogeneity and stability has been verified; after characterization, the material has been certified as ERM-DA470k/IFCC. We characterized the candidate reference material for 14 proteins by applying a protocol that is considered to be a reference measurement procedure, by use of optimized immunoassays. ERM-DA470 was used as a calibrant. For 12 proteins [α(2) macroglobulin (A2M), α(1) acid glycoprotein (orosomucoid, AAG), α(1) antitrypsin (α(1)-protease inhibitor, AAT), albumin (ALB), complement 3c (C3c), complement 4 (C4), haptoglobin (HPT), IgA, IgG, IgM, transferrin (TRF), and transthyretin (TTR)], the results allowed assignment of certified values in ERM-DA470k/IFCC. For CRP, we observed a bias between the lyophilized and liquid frozen materials, and for CER, the distribution of values was too broad. Therefore, these 2 proteins were not certified in the ERM-DA470k/IFCC. Different value transfer procedures were tested (open and closed procedures) and found to provide equivalent results. A new serum protein reference material has been produced, and values have been successfully assigned for 12 proteins.

Certified reference materials (CRMs) play a crucial role in ensuring the quality of analytical measurements. Particularly, the EU labelling legislation on genetically modified organisms (GMOs) in food and feed products explicitly requires CRMs for its implementation. The CRMs are used to calibrate and control the quantitative real-time polymerase chain reaction (qPCR) method and support official control laboratories, such as National Reference Laboratories (NRLs), in maintaining their ISO/IEC 17025 accreditation. The Joint Research Centre of the European Commission (EC JRC) is specialized in the production of reference materials and has been producing GMO CRMs since 1998. Together with a validated event-specific qPCR method, these GMO CRMs form the EU reference system for the quantification of EU-authorized GMO events in food and feed products and ensure a common GMO labelling threshold. This article gives a retrospective view on the more than 25 years of GMO CRM production at JRC. It describes requirements for GMO CRMs in view of an EU market authorization under (EC) No. 1829/2003. The evolution and major improvements of the production of GMO CRMs at JRC are summarized as well as the current understanding of the EU’s GMO reference system for GMO quantification and its impact on commutability. It provides insights into GMO CRM sales and their worldwide distribution. This information may be useful for policymakers and researchers in understanding the current EU GMO measurement landscape and to anticipate possible future demands related to GMO events based on new genomic techniques (NGTs).

When performing effect studies to investigate the impact of microplastic (MP) on cell lines, algae, or daphnia, it is advantageous if such experiments can be performed without the use of surfactants. The need for surfactants arises from the fact that finely milled pristine MP particles generally are hydrophobic. Methods for the preparation of larger amounts of hydrophilic and hence artificially aged MP particles and approaches for their characterization are of high importance. Here we present methods to artificially age polyethylene terephthalate (PET) and low-density polyethylene (PE) using alkaline and acidic treatments that reproducibly result in large quantities of particles below 5 µm with considerably increased hydrophilicity. The artificially aged MP particles were characterized using particle counting by single-particle extinction and scattering (SPES), particle size by laser diffraction measurements, zeta potential using electrophoretic light scattering, hydrophobicity index (Hy) through dark-field (DF) microscopy, chemical composition by inductively coupled plasma-mass spectrometry (ICP-MS), Fourier transform infrared (FTIR) microscopy, and Raman microscopy. The hydrophobicity index values obtained should allow the aged MP particles to be characterized as qualitative reference materials (RMs) with an ordinal property. Evidence for the maintained integrity and hydrophilicity of the artificially aged MP particles (in powder form) over time was obtained by measurements of zeta potential with a 33-month interval. Uniformity of subsampling with respect to particle number concentration in suspensions within a 10-day period was also investigated. It provided evidence for the possibility of reproducible spiking of a specific number of hydrophilic MP particles with relative standard deviations (RSDs) from 6.2 to 13.6%. For the development of future reference materials of artificially aged microplastics, they should be characterized for an ordinal property (artificial age as Hy-index) and nominal property (identity of PET or PE based on spectral matching). Graphical Abstract

Roundup Ready soybean powder has been subjected to different amounts of DNA fragmentation to assess the accuracy of real-time PCR on processed food. Certified reference material (CRM) containing 10 g kg-¹ of Roundup Ready soybean (ERM-BF410d) prepared by a dry-mixing processing method was exposed to water at two temperatures, using three different mixing devices, or to baking temperature (250°C) for 30 min. The amount of DNA extracted from the different samples was quantified by fluorimetry. The amount of fragmentation of the extracted DNA was characterised by gel and capillary electrophoresis and the percentage of genetically modified (GM) soybean was determined by a double quantitative real-time PCR method. Measurement of the event GTS 40-3-2 (RUR) was possible in all the treated materials, because small amplicons were amplified. Correct RUR percentages could be measured for intact powders with little or no DNA fragmentation. For samples with a high level of DNA degradation, however, the accuracy of the measurement was found to depend on the method used for DNA extraction. Genomic DNA isolated by use of silica resin resulted in statistically significant overestimation of the amount of GM.

The number of reference materials (RMs), including certified reference materials (CRMs) characterized for qualitative properties, has steadily increased in recent years. In response, the Technical Committee for Reference Materials of the International Organization for Standardization, ISO/TC 334, developed ISO 33406 to provide guidance to reference material producers (RMPs) on producing qualitative RMs. ISO 33406 builds on the general requirements in ISO 17034:2016 for RMP competence and offers specific guidance on value assignment, assessment of homogeneity and stability, statement of metrological traceability, and measurement uncertainty evaluation for RMs with qualitative property values.

Different methods for ceruloplasmin tend to give different results in external quality assessment schemes. During the production of the certified reference material ERM-DA470k/IFCC discrepant measurement results were also found for ceruloplasmin measured with different methods, and consequently the protein could not be certified in the material. We performed a commutability study with 30 serum samples and the reference materials ERM-DA470, ERM-DA470k/IFCC, and ERM-DA472/IFCC, using 6 different methods. Data were analyzed according to the CLSI Guideline C53-A to assess whether the reference materials had the same behavior as the serum samples with respect to measurement results obtained with combinations of the methods used. Measurement results from different methods showed a good linear correlation for the serum samples. ERM-DA470 showed marked noncommutability for certain combinations of methods. ERM-DA470k/IFCC and ERM-DA472/IFCC were commutable for more combinations of methods. The lack of commutability of ERM-DA470 for certain combinations of methods correlates with results from the UK National External Quality Assessment Service showing discrepancies between results from these methods. For serum stored in the presence of sodium azide the results from different methods are essentially equivalent. Ceruloplasmin in ERM-DA470 is a fully documented example of a situation in which, due to lack of commutability, the use of a common material for calibration did not lead to harmonization .

The International Organization for Standardization (ISO) has published ISO 17034:2016 on the general requirements for the competence of reference material producers (RMPs). Previously, these requirements were addressed in ISO Guide 34:2009, originally developed by the ISO Committee on Reference Materials (ISO/REMCO). The need for an International Standard was triggered as several accreditation bodies could not accredit to a guide, at all, while in other countries ISO Guide 34 could only serve as accreditation standard in combination with ISO/IEC 17025. For the transformation into a conformity assessment standard of the ISO/IEC 17000 series, the ISO Committee on Conformity assessment (ISO/CASCO) and ISO/REMCO joined forces. A Joint Working Group, formed by experts and stakeholders from both committees, finalised the transformation within 2 years. During the transformation, the structure of ISO 17034 has been aligned with other ISO/IEC 17000 series standards and the content of ISO 17034 has been harmonised with the recent editions of other relevant ISO Guides. Requirements for the production of reference materials (RMs) were elaborated on more clearly in the new standard, specifying the requirements for (non-certified) reference materials and the additional requirements for certified reference materials. The new International Standard ISO 17034:2016 supersedes ISO Guide 34:2009.

Despite the fact that the measurement unit for the quantification of GMOs in food and feed products has not yet been unambiguously agreed upon in Europe, international trade requires reliable GMO analysis measuring comparably the GMO content of products. The two reference systems, based either on mass fractions or on copy number ratios, and their metrological traceability chains are presented and discussed. It is concluded that, properly established and expressed, measurement results in copy number ratios can provide a metrologically sound reference system. In this case, certified reference materials used for calibration and quality control can be independent of each other and the uncertainty derived from calibration can correctly be included in the overall uncertainty of the GMO measurement. However, further efforts are required to establish this metrological system.

NRC publication: Yes