Certified Reference materials

Cyclic imines (CIs) are being considered as emerging toxins in the European Union, and a scientific opinion has been published by the European Food Safety Authority (EFSA) in which an assessment of the risks to human health related to their consumption has been carried out. Recommendations on the EFSA opinion include the search for data occurrence of CIs in shellfish and using confirmatory methods by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which need to be developed and optimized. The aim of this work is the application of LC-MS/MS to the analysis of gymnodimines (GYMs), spirolides (SPXs), pinnatoxins (PnTXs), and pteriatoxins (PtTXs) in mussels from Galician Rias, northwest Spain, the main production area in Europe, and therefore a representative emplacement for their evaluation. Conditions were adjusted using commercially available certified reference standards of GYM-A, SPX-1, and PnTX-G and evaluated through quality control studies. The EU-Harmonised Standard ...

Актуальность исследования обусловлена значительным интересом ученых, работающих в области угольной геологии, и специалистов химико-аналитических лабораторий, практикующих элементный количественный анализ объектов окружающей среды, к проблематике высокоточного определения низких содержаний химических элементов в углях и угольных материалах для последующего применения полученных данных при решении научных и различных технологических задач. Цель: рассмотреть и обобщить наиболее часто используемые методические подходы к определению химических элементов в широком диапазоне их содержаний в углях (угольных материалах), а также оценить правильность и точность результатов метода ИСП-МС после открытого кислотного разложения проб и их сплавления с метаборатом лития, сопоставлением получаемых данных с результатами метода ИНАА и статистической обработкой данных. Объекты: угли, углистые алевролиты и углефицированная древесина месторождения германия Спецугли, расположенного на юго-западной окраине...

The “purity” of an organic compound typically refers, in practice, to an assignment of the mass fraction content of the primary organic component present in the material. The “purity” value of an organic primary calibrator material is the ultimate source of metrological traceability of any quantitative measurement of the content of that compound in a given matrix. The primary calibrator may consist of a Certified Reference Material (CRM) whose purity has been assigned by the CRM producer or a laboratory may choose to value-assign a material to the extent necessary for their intended application by using appropriately valid methods. This report provides an overview of the approach, performance and applicability of the principal methods used to determine organic purity including mass balance, quantitative NMR, thermal methods and direct-assay techniques. A statistical section reviews best practice for combination of data, value assignment as the upper limit values corresponding to 100...

B-type natriuretic peptide (BNP) is a 32 amino acid cardiac hormone routinely measured by immunoassays to diagnose heart failure. While it is reported that immunoassay results can vary up to 45%, no attempt of standardization and/or harmonization through the development of certified reference materials (CRMs) or reference measurement procedures (RMPs) has yet been carried out. B-type natriuretic peptide primary calibrator was quantified traceably to the International System of Units (SI) by both amino acid analysis and tryptic digestion. A method for the stabilization of BNP in plasma followed by protein precipitation, solid phase extraction (SPE) and liquid chromatography (LC) mass spectrometry (MS) was then developed and validated for the quantification of BNP at clinically relevant concentrations (15-150 fmol/g). The candidate reference method was applied to the quantification of BNP in a number of samples from the UK NEQAS Cardiac Markers Scheme to demonstrate its applicability ...

Environmental context. Arsenic can be found in all environmental compartments in a large number of chemical forms of varying toxicity. We performed an inter-laboratory comparison study focusing on quantitation of some of the most toxic arsenic forms in seven different biological materials and found very good agreement among the submitted results. Certification of the studied materials will provide suitable quality control samples for environmentally relevant concentrations of arsenic in food products and biota.

An ultra sensitive method for arsenic (As) speciation analysis based on selective hydride generation (HG) with preconcentration by cryotrapping (CT) and inductively coupled plasma- mass spectrometry (ICP-MS) detection is presented. Determination of valence of the As species is performed by selective HG without prereduction (trivalent species only) or with L-cysteine prereduction (sum of tri- and pentavalent species). Methylated species are resolved on the basis of thermal desorption of formed methyl substituted arsines after collection at −196°C. Limits of detection of 3.4, 0.04, 0.14 and 0.10 pg mL−1 (ppt) were achieved for inorganic As, mono-, di- and trimethylated species, respectively, from a 500 μL sample

This work describes the method of a selective hydride generation-cryotrapping (HG-CT) coupled to an extremely sensitive but simple in-house assembled and designed atomic fluorescence spectrometry (AFS) instrument for determination of toxicologically important As species. Here, an advanced flame-in-gas-shield atomizer (FIGS) was interfaced to HG-CT and its performance was compared to a standard miniature diffusion flame (MDF) atomizer. A significant improvement both in sensitivity and baseline noise was found that was reflected in improved (4 times) limits of detection (LODs). The yielded LODs with the FIGS atomizer were 0.44, 0.74, 0.15, 0.17 and 0.67 ng L–1 for arsenite, total inorganic, mono-, dimethylated As and trimethylarsine oxide, respectively. Moreover, the sensitivities with FIGS and MDF were equal for all As species, allowing for the possibility of single species standardization with arsenate standard for accurate quantification of all other As species. The accuracy of HG-...

An ultra sensitive method for arsenic (As) speciation analysis based on selective hydride generation (HG) with preconcentration by cryotrapping (CT) and inductively coupled plasmamass spectrometry (ICP-MS) detection is presented. Determination of valence of the As species is performed by selective HG without prereduction (trivalent species only) or with L-cysteine prereduction (sum of tri-and pentavalent species). Methylated species are resolved on the basis of thermal desorption of formed methyl substituted arsines after collection at -196°C. Limits of detection of 3.4, 0.04, 0.14 and 0.10 pg mL -1 (ppt) were achieved for inorganic As, mono-, di-and trimethylated species, respectively, from a 500 μL sample. Speciation analysis of river water (NRC SLRS-4 and SLRS-5) and sea water (NRC CASS-4, CASS-5 and NASS-5) reference materials certified to contain 0.4 to 1.3 ng mL -1 total As was performed. The concentrations of methylated As species in tens of pg mL -1 range obtained by HG-CT-ICP-MS systems in three laboratories were in excellent agreement and compared well with results of HG-CT-atomic absorption spectrometry and anion exchange liquid chromatography-ICP-MS; sums of detected species agreed well with the certified total As content. HG-CT-ICP-MS method was successfully used for analysis of microsamples of exfoliated bladder epithelial cells isolated from human urine. Here, samples of lysates of 25 to 550 thousand cells contained typically tens pg up to ng of iAs species and from single to hundreds pg of methylated species, well within detection power of the presented method. A significant portion of As in the cells was found in the form of the highly toxic trivalent species.

This work describes the method of a selective hydride generation-cryotrapping (HG-CT) coupled to an extremely sensitive but simple in-house assembled and designed atomic fluorescence spectrometry (AFS) instrument for determination of toxicologically important As species. Here, an advanced flame-in-gas-shield atomizer (FIGS) was interfaced to HG-CT and its performance was compared to a standard miniature diffusion flame (MDF) atomizer. A significant improvement both in sensitivity and baseline noise was found that was reflected in improved (4 times) limits of detection (LODs). The yielded LODs with the FIGS atomizer were 0.44, 0.74, 0.15, 0.17 and 0.67 ng L -1 for arsenite, total inorganic, mono-, dimethylated As and trimethylarsine oxide, respectively. Moreover, the sensitivities with FIGS and MDF were equal for all As species, allowing for the possibility of single species standardization with arsenate standard for accurate quantification of all other As species. The accuracy of HG-CT-AFS with FIGS was verified by speciation analysis in two samples of bottled drinking water and certified reference materials, NRC CASS-5 (nearshore seawater) and SLRS-5 (river water) that contain traces of methylated As species. As speciation was in agreement with results previously reported and sums of all quantified species corresponded with the certified total As. The feasibility of HG-CT-AFS with FIGS was also demonstrated by the speciation analysis in microsamples of exfoliated bladder epithelial cells isolated from human urine. The results for the sums of trivalent and pentavalent As species corresponded well with the reference results obtained by HG-CT-ICPMS (inductively coupled plasma mass spectrometry).

Concentrations of amino acids in a human plasma pool were determined using four independent quantification methods. Orthogonal separation schemes (LC, GC, or GC×GC) and detection systems (triple quadrupole or time-of-flight mass spectrometry) are shown to demonstrate excellent consistency among platforms for quantifying 18 amino acids in NIST Standard Reference Material (SRM) 1950 Metabolites in Human Plasma using a well-characterized isotope dilution (ID) quantification method. Measured levels were consistent with reference values in plasma from the literature. Individual amino acid concentrations in plasma varied by over an order of magnitude ranging from 1.83 g/g to 28.0 g/g (7.78 mol/L to 321 mol/L). Average variability (coefficient of variation) between experimental amino acid concentrations (excluding cysteine) among all methods was 6.3%. Certified mass fraction values for amino acids in NIST SRM 1950 will be established from statistically weighted means of all experimental results.

A novel hydrophobic sorbent material for on-line column preconcentration and separation systems coupled with atomic spectrometry was developed. Poly(etheretherketone) (PEEK) in the form of turnings was used as packing material and evaluated for trace lead determination in environmental samples. Sample and ammonium diethyl-dithiophosphate (DDPA) reagent were mixed on-line and the Pb(II)-DDPA complex was retained effectively on PEEK-turnings. Isobutyl methyl ketone (IBMK) was adopted for efficient analyte complex elution and subsequently transportation into the nebulizer-burner system for atomization. The developed sorbent material has shown, excellent chemical and mechanical resistance, fast adsorption kinetics permitting the use of high sample flow rates without significant loss of retention efficiency. For 120 s sample preconcentration time the sampling frequency was 20 h -1 , the enhancement factor was 110, the detection limit (3 s) was c L = 0.32 g L -1 , and the relative standard deviation (RSD) was s R = 2.2%, at the 50.0 g L -1 Pb(II) level. The accuracy of the developed method was evaluated by analyzing certified reference materials.

A novel automatic sequential injection (SI) single-drop micro-extraction (SDME) system is proposed as versatile approach for on-line metal preconcentration and/or separation. Coupled to electrothermal atomic absorption spectrometry (ETAAS) the potentials of this SI scheme are demonstrated for trace cadmium determination in water samples. A non-charged complex of cadmium with ammonium diethyldithiophosphate (DDPA) was produced and extracted on-line into a 60 L micro-drop of di-isobutyl ketone (DIBK). The extraction procedure was performed into a newly designed flow-through extraction cell coupled on a sequential injection manifold. As the complex Cd(II)-DDPA flowed continuously around the micro-droplet, the analyte was extracting into the solvent micro-drop. All the critical parameters were optimized and offered good performance characteristics and high preconcentration ratios. For 600 s microextraction time, the enhancement factor was 10 and the sampling frequency was 6 h -1 . The detection limit was 0.01 g L -1 and the precision (RSD at 0.1 g L -1 of cadmium) was 3.9%. The proposed method was evaluated by analyzing certified reference material.

This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM 10 , which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurement which consist of a microwave digestion followed by analysis with either ICP-MS or GFAAS. Each participant was asked to analyse five test samples: a liquid Certified Reference Material (CRM), two sub-samples of a NIST dust CRM (one already-digested and one to be digested by the participants) and two loaded filters (one already-digested and one to be digested by the participants). Participants were able to meet the Data Quality Objectives (DQOs) of the European Directives (expanded uncertainties of 25% for Pb and 40% for As, Cd and Ni) for 93% of all test samples, except for the loaded filter that were digested by the participants. In fact, only 76% of DQOs were met for this test sample, the closest to a routine sample analysis in the laboratory. The difficulties in analysing this test sample came mainly from digestion and contamination processes. Satisfactory results were also obtained using other digestion techniques (Soxhlet extraction and high pressure methods) and analytical methods (ICP-OES for Cd, Ni and Pb, EDXRF for Pb and Ni and Voltammetry for As, Ni, and Pb). Participants claimed uncertainties of about 10% for Pb and between 15 and 20% for As, Cd and Ni. These uncertainties were confirmed for 77% of results. The reproducibility of the methods of measurement was between 41 and 54% while repeatability remained between 5 and 12% except for the analysis of As on filters which was up to 20%. The majority of participant results showed higher between-day variability (14 AE 11%) than within-day variability (6.0 AE 5.3%).

Several microwave-assisted digestion methods were tested at the Centro de Estudios Aplicados en Química laboratory in Quito, Ecuador, to determine the accuracy and performance efficiency of the mineralization process for the determination of total mercury in fish tissue by cold vapor atomic fluorescence spectrophotometry. The use of MARSEasyPrep high-pressure vessels, low amounts of reagents (1 cm3 HNO3, 1 cm3 H2O2, and 1 cm3 HClO4), an irradiation temperature of 210 °C, and 35 min of mineralization time resulted in accurate performance, with recoveries of certified reference material DORM-4 between 90.1% and 105.8%. This is better than the Association of Official Analytical Chemists 2015.01 method, which has a reported accuracy of 81%. The repeatability precision and intermediate precision were established at three concentration levels (0.167, 0.500, and 0.833 mg·kg−1) and expressed as the percentage of the relative standard deviation ranging from 1.5% to 3.0% and 1.7% to 4.2%, res...

Oilseeds from five native plant species with edible potential from the Brazilian Caatinga semi-arid region (Diplopterys pubipetala, Barnebya harleyi, Croton adamantinus, Hippocratea volubilis, and Couroupita guianensis) were investigated regarding their mineral contents. The minerals, Na, K, Ca, Mg, Fe, Cu, Cr, Al, were analyzed by high-resolution continuum source atomic absorption spectrometry (HR–CS AAS) and P by the vanadomolybdophosphoric acid colorimetric method. K, Mg, and P were the main elements found (1.62–3.7 mg/g, 362–586 µg/g, and 224–499 µg/g dry weight (dw), respectively). B. harley seeds contained the highest amounts of K and P, while C. guianensis seeds were the richest in Mg. Fe was the most abundant oligoelement (2.3–25.6 µg/g dw). Cr contents were below the limit of quantification for all samples and Al amounts were low: 0.04–1.80 µg/g dw. A linear discriminant analysis clearly differentiated B. harleyi and C. guianensis samples from the remaining ones. In sum, th...

It is important that analytical results, produced to demonstrate compliance with exposure limits are comparable, to ensure controls are monitored to similar standards. Correcting a measurement result of respirable alpha-quartz for the percentage of crystalline material in the calibration dust is good analytical practice and significant changes in the values assigned to calibration materials will affect the interpretation of results by an analyst or occupational hygiene professional. The reissue of the certification for the quartz reference material NIST 1878a in 2005 and differences in comparative values obtained by other work created uncertainty about the values of crystallinity assigned to national calibration dusts for alpha-quartz. Members of an International Organization for Standardization working group for silica measurement ISO/TC146/SC2/WG7 collaborated to investigate the comparability of results by X-ray diffraction (XRD) and to reach a consensus. This paper lists the valu...

Proficiency tests are inter-laboratory exercises in which the results of a particular laboratory arsenic in fish tissues. Therefore, this study describes a new protocol for the production of reference mare compared to a reference value or with the results obtained from similar laboratories. A proficiency test item is required for the effective execution of these tests, which can be: a sample product or device, reference material, equipment, a standard set of data or other information. In Brazil there are currently no providers of proficiency testing for toxic metals such as materials for use in proficiency testing for arsenic in fish tissue. The reference materials produced for proficiency testing should be homogeneous and stable over the duration of the test, and must follow all the requirements of international quality standards used in the preparation of certified reference materials. The preparation scheme consisted of: selecting of individuals, cleaning of scale and skin, trituration, homogenization, and spiking with arsenic at two levels of concentration, irradiated with cobalt 60 at 10.00 ± 1.05 kGy and packed into sachets.

Proficiency tests are inter-laboratory exercises in which the results of a particular laboratory arsenic in fish tissues. Therefore, this study describes a new protocol for the production of reference mare compared to a reference value or with the results obtained from similar laboratories. A proficiency test item is required for the effective execution of these tests, which can be: a sample product or device, reference material, equipment, a standard set of data or other information. In Brazil there are currently no providers of proficiency testing for toxic metals such as materials for use in proficiency testing for arsenic in fish tissue. The reference materials produced for proficiency testing should be homogeneous and stable over the duration of the test, and must follow all the requirements of international quality standards used in the preparation of certified reference materials. The preparation scheme consisted of: selecting of individuals, cleaning of scale and skin, tritu...

This paper proposes a method to determine selenium in samples of fish muscle and liver tissue using ultrasound assisted extraction process, and analysed by graphite furnace atomic absorption spectrometry (GFAAS). The selenium content was extracted by 0.10 M HCl at the optimal extraction conditions which were established as follows: sample mass of 100 mg; granulometry of the sample <60 µm; sonication time of five 40 s cycles; and sonication power of 136 W. The selenium determinations were performed by GFAAS, at a drying temperature of 120°C/250°C, pyrolysis temperature of 1300°C, atomization temperature of 2300°C, and cleaning temperature of 2800°C. Palladium nitrate was used as a chemical modifier coinjected with the samples, and tungsten as a permanent modifier. The concentration of selenium determined in the pool of fish muscle and liver tissue were 280.4±4.2 e 592.3±6.7 μg kg−1, respectively. The accuracy and precision of the proposed extraction method were evaluated using cer...

A new sample treatment methodology was developed for the simultaneous determination of oleic, linoleic, palmitic and stearic fatty acids (FA), and α-, β-, γ-and δ-tocopherol homologues in peanut samples. Usually, the determination of these compounds is carried out after oil extraction with an organic solvent at boiling temperatures of the solvent. The innovative analytical methodology developed in this work was performed in a 20 mL vial in which the FA and tocopherols were simultaneously extracted, and the derivatization of the FA was, afterwards, conducted. The reduction in analysis time from 1 h 30 min (reference methodology) to 20 min (new methodology) increased the sample throughput. Furthermore, the amount of organic solvent used decreased from 40 mL to 6 mL The new methodology was validated based on the analysis of a certified reference peanut butter sample and the results were compared to those obtained by using the reference methodology and a suitable agreement with the certified values was found. Finally, the new sample treatment approach was used to analyse toasted and fried (with and without tegument) peanuts.

We use conventional, microwave and ultrasound assisted sequential extraction, of defined time and power, techniques for extractions of Cd, Cu, Cr, Ni, Pb and Zn in sediments and certified material. We did not change the conditions of extractions through steps, cause we what to see is there difference in extraction results for the certified material and sediments. We use lower powers and time from microwave and ultrasound extraction in order to avoid additional heating and boiling of the samples. Steps 1-3 of the BCR (Community Bureau of Reference), excluding the hydrogen peroxide digestion in step 3, were completed in 16 h in the conventional, in 120 s with 90 W power of microwave and in 30 min of 42 kHz of an ultrasonic frequency. Digestion of organic matter with hydrogen peroxide was performed the same for all techniques. The fourth step, the pseudo-total content, was performed the same on samples remaining after performing the extraction of the previous three phases either conventionally, microwave-assisted or with ultrasound. The precision and accuracy of the proposed procedures were evaluated using a certified reference material BCR701. Acceptable accuracy for most of the metals was observed for all three steps of BCR protocol applying a 16 h total shaking period. Metals were determined with an acceptable accuracy after the pseudo-total step; expect Cr. Results obtained after the application of different techniques on sediments were comparable with ANOVA test for the 95 % of confidence level.

Ocean observations are critical in developing our understanding of the interaction between the ocean and climate. Detailed information about the nutrient composition of the ocean is achieved using in situ sensing and the collection and analysis of physical samples from research vessels. The analysis of nutrients underpins work in understanding both the carbon cycle and biological productivity in oceans. Although in situ sensors are becoming more common for some nutrients, the best and most reliable method for making these measurements is to conduct analysis of physical samples at sea. This article discusses the analysis and data processing methods developed by the hydrochemistry team at Commonwealth Scientific and Industrial Research Organisation (CSIRO) to provide repeatable and accurate analysis of nutrient samples at sea. Nutrients are measured by segmented flow analysis and data are processed using in‐house software (Hydrology Processor [HyPro]). These methods were used during t...

Metabolic phenotyping using mass spectrometry (MS) is being applied to ever increasing sample numbers in clinical and epidemiology studies. High-throughput and robust methods are being developed for the accurate measurement of metabolites associated with disease. Traditionally, quantitative assays have utilized triple quadrupole (QQQ) MS based methods; however, the use of such focused methods removes the ability to perform discovery-based metabolic phenotyping. An integrated workflow for the hybrid simultaneous quantification of 34 biogenic amines in combination with full scan high-resolution accurate mass (HRAM) exploratory metabolic phenotyping is presented. Primary and secondary amines are derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate prior to revered-phase liquid chromatographic separation and mass spectrometric detection. Using the HRAM-MS data, retrospective phenotypic data mining could be performed, demonstrating the versatility of HRAM-MS instrumentation in a clinical and molecular epidemiological environment. Quantitative performance was assessed using two MS detector platforms: Waters TQ-XS (QQQ; n = 3) and Bruker Impact II QToF (HRAMS-MS; n = 2) and three human biofluids (plasma, serum and urine). Finally, each platform was assessed using a certified external reference sample (NIST SRM 1950 plasma). Intra-and inter-day accuracy and precision were comparable between the QQQ and QToF instruments (<15%), with excellent linearity (R 2 > 0.99) over the quantification range of 1-400 μmol L -1 . Quantitative values were comparable across all instruments for human plasma, serum and urine samples, and calculated concentrations were verified against certified reference values for NIST SRM 1950 plasma as an external reference. As a real-life biological exemplar, the method was applied to plasma samples obtained from SARS-CoV-2 positive patients versus healthy controls. Both the QQQ and QToF approaches were equivalent in being able to correctly classify SARS-CoV-2 positivity. Critically, the use of HRAM full scan data was also assessed for retrospective exploratory mining of data to extract additional biogenic amines of biomarker interest beyond the 34 quantified targets.

A method for the simultaneous determination of As, Hg, Se and Sn in sediment slurries using chemical vapor generation (CVG), in situ trapping electrothermal vaporization inductively coupled plasma mass spectrometry, is proposed. The vapors produced by the reaction of the sample slurry with the reducing agent are transported to the vaporizer and trapped at 150 uC in a graphite tube, treated with Ir as a permanent modifier, before vaporization at 2000 uC and transport to the plasma. The accuracy of the method was assured by the analysis of certified reference sediment samples, using external calibration with aqueous solutions, prepared in the same medium and subject to the same CVG and trapping procedure as the slurries. The obtained concentrations were in agreement with the certified values, using the t-Student test for a confidence level of 95%. The detection limits, in ng g 21 , were: 0.8 for Hg, 0.04 for As, 0.01 for Se and 0.30 for Sn.

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 mg L À1 and 2.6 mg L À1 , respectively. A precision expressed as relative standard deviation (RSD, n ¼ 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10 mg L À1 and 30 mg L À1 , respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10 mg L À1 and 30 mg L À1 , respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhe´us and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.

IntroductionReference materials based on human cerebrospinal fluid were certified for the mass concentration of amyloid beta (Aβ)1‐42 (Aβ42). They are intended to be used to calibrate diagnostic assays for Aβ42.MethodsThe three certified reference materials (CRMs), ERM‐DA480/IFCC, ERM‐DA481/IFCC and ERM‐DA482/IFCC, were prepared at three concentration levels and characterized using isotope dilution mass spectrometry methods. Roche, EUROIMMUN, and Fujirebio used the three CRMs to re‐calibrate their immunoassays.ResultsThe certified Aβ42 mass concentrations in ERM‐DA480/IFCC, ERM‐DA481/IFCC, and ERM‐DA482/IFCC are 0.45, 0.72, and 1.22 μg/L, respectively, with expanded uncertainties (k = 2) of 0.07, 0.11, and 0.18 μg/L, respectively. Before re‐calibration, a good correlation (Pearson&#39;s r &gt; 0.97), yet large biases, were observed between results from different commercial assays. After re‐calibration the between‐assay bias was reduced to &lt; 5%.DiscussionThe Aβ42 CRMs can ensure t...