Development of a certified reference material for the determination of perfluorooctanoic acid

A certified reference material (CRM) for the determination of perfluorooctanoic acid (PFOA) has been issued as NMIJ CRM 4056-a by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Purity (kg kg^?1) based on a titration method was determined by subtracting the mass fractions of impurities measured using liquid chromatography/mass spectrometry (LC/MS) from those of acids expressed as PFOA measured by a neutralization potentiometric titration. To validate an obtained result, purity based on a mass balance method was determined by subtracting the mass fractions of impurities, measured using LC/MS, Karl-Fischer titration (KFT), and vacuum evaporation, from 1 kg kg^?1. Results from both titration and mass balance methods were in agreement within the accepted limits of uncertainty. The certified purity of NMIJ CRM 4056-a was determined to be 0.959 kg kg^?1, calculated as the mean of the results obtained with the two methods. The standard uncertainty of the certified purity was evaluated from purity evaluations as well as from sample homogeneity and stability obtained from LC/MS and KFT analyses. Consequently, the expanded uncertainty was estimated to be 0.005 kg kg^?1 with a coverage factor of k = 2.     

Development of a certified reference material for the determination of acrylamide in potato chips

A certified reference material (CRM), KRISS CRM 108-10-003, has been developed for analysis of acrylamide in potato chips, as a representative of carbohydrate-rich food cooked in high-temperature oil. The material was prepared by grinding commercially available potato chips to a paste which was then homogenized, bottled in 15-g units, and stored at ?70 °C. Certification, homogeneity and stability testing, were carried out by liquid chromatography–isotope-dilution mass spectrometry (ID-LC–MS). A single ID-LC–MS measurement was performed for each of 10 selected units for certification and homogeneity assessment. The mean measurement result for the 10 bottles, 0.455?±?0.012 mg?kg^?1, was assigned as the certified value of the CRM. The between-bottle homogeneity was 0.8% of the certified value. The within-bottle homogeneity, tested by measuring three replicate sub-samples from each of three randomly selected bottles, was similar to the between-bottle homogeneity. The stability of the CRM under storage conditions (?70 °C) was tested for 21 months and no change in the acrylamide content was observed within the measurement uncertainty. Stability of the CRM at –20 °C (storage at user’s site) and room temperature (for regular use and transportation) was also tested. Also presented is the newly designed procedure for evaluating the uncertainty of the certified value for the characterization scheme used in this study.

A set of four soil reference materials with certified values of total element contents and their extractable fractions

A set of certified reference materials of four natural soils denoted as CRM 7001-4 was prepared. They consist of light sandy soils with normal and elevated, silty clay loam with normal, and loam with elevated element levels. Certified and/or information values were established for the total contents of the elements As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, Zn, and their fractions, extractable with aqua regia, and boiling and cold 2 mol L^–1 nitric acid, from results of a 28 laboratory intercomparison using various methods of atomic absorption spectrometry, optical emission spectrometry, mass spectrometry, electrochemical methods, spectrophotometry, instrumental neutron activation analysis, and X-ray fluorescence.     

Preparation of a calibrant as certified reference material for determination of the Fusarium mycotoxin zearalenone

In the field of mycotoxin analysis, substantial problems shown by high between-laboratory standard deviations and noncomparable and nontraceable results have been caused by the lack of proper calibrants for external calibration. During a large-scale Standard Measurement and Testing project of the European Commission (EC) dealing with preparation and certification of reference materials for determination of the mycotoxin zearalenone (ZON) in maize, a ZON calibrant in acetonitrile was prepared and checked for purity, homogeneity, and stability. Before certification, on the basis of preparation, the calibrant was checked in a mini-interlaboratory study by UV spectrophotometric determination. The molar absorptivities of ZON in acetonitrile at 236, 274, and 314 nm were established, and as a main result, a common reference wavelength of 274 nm with molar absorptivity of 12623 +/- 111 L/mol x cm can be recommended for ZON in acetonitrile. A concentration and expanded uncertainty of the ZON calibrant of 9.95 +/- 0.08 microg/mL was calculated as a preliminary value before final evaluation through the certification panel of the EC.     

INAA and PIXE for the determination of the contents of extractable sediment

The three-stage BCR sequential step reference extraction procedure was applied to the reference material BCR CRM 601, especially developed for fractionation studies. Extracted fractions were analyzed for Cr, Ni, Zn, Cd, and Pb, by k ₀-standardized instrumental neutron activation (k ₀ INAA) and proton induced X-ray emission (PIXE), and flame atomic absorption spectrometry (FAAS). Sample preparation procedures were developed for both k ₀ INAA and PIXE techniques, related to the evaporation of the solutions in order to get solid samples for neutron and proton irradiation. Quality control was assessed by intercomparison of the analytical results obtained by the applied techniques, which included results for a few certified reference materials. In the extracted fractions, chromium concentration was not determined accurately by both nuclear techniques. Concerning Cd, Ni, Pb, and Zn, the results were in general in good agreement with the certified values and FAAS. Some incomplete separation of the residue might have occurred.     

Accreditation system for reference material producers and certified reference materials for iron and steel in Japan

  ISO 9000 series strictly requires traceability to national or international measurement standards. It is becoming more necessary to make clear the concept of traceability of measurement standards with respect to chemical composition and to accredit the reference material producers. In Japan, the accreditation system for reference material producers is considered to satisfy the requirement of ISO Guide 34, ISO 9000 series and ISO/IEC Guide 25, while the producer fulfills the concept of traceability of measurement standards. This paper describes the production of iron and steel reference materials in Japan relating to the international standardization of methods (written standards) and accreditation of reference material producers. Received: 11 October 1996 Accepted: 5 December 1996     

Development of a certified reference material for lead in noodles powder

Accreditation and Quality Assurance - Food Safety and Standards Authority of India has set maximum permissible level of lead in noodle at 2.5 mg/kg. The standardized lead measurement is of high...     

New certified reference material for general use in the determination of trace elements in the environment: Single cell protein

The way of certification of trace element contents in a sample of single cell protein (SCP) is presented together with the results of the homogeneity and stability studies, carried out on this sample (BCR 274). The elements As, Cd, Co, Cu, Mn, Pb, Se and Zn are certified using different spectrometric, electrochemical or activation techniques after a thorough sample treatment. The material is not only useful in SCP-analysis, but can also be applied for analytical background measurements and control or for the analysis of similar materials (e.g. sea food).     

A greener microwave-assisted extraction method for rapid spectroscopic determination of selected metals in river and freshwater sediment certified reference materials

The current study describes development of novel, cost-effective, rapid and greener microwave-assisted extraction (MW-AE) method using diluted hydrogen peroxide (H₂O₂) and 400 µL of concentrated aqua-regia for the extraction of 10 selected metals (Ba, Cr, Cu, Co Fe, Mn, Ni, Pb, V and Zn) in sediment certified reference materials (CRMs), prior to inductively coupled plasma-optical emission spectroscopic analysis. The optimum extraction conditions were achieved when 0.2 g of sediment was extracted with 1 mol L^?1 of H₂O₂ (12.00 mL) and 400 µL of concentrated aqua-regia, at 180°C microwave extraction temperature for 30 min. Accuracy of the proposed MW-AE method was evaluated by using river (LGC6187) and freshwater (CRM015-050) sediment CRMs. Quantitative extraction recoveries of 80–120% in LGC6187 and 74–124% in CRM0150-050 were obtained with acceptable precision (0.4–1.0%). The proposed extraction method has a clear advantage over classical approaches as 1 mol L^?1 H₂O₂ was used instead of notorious acidic mixture (Hydrochloric acid/ nitric acid/ hydrofluoric). The method detection limits (MDLs) of 0.03–0.9 μg g^?1 were obtained for all the investigated metals and were fairly comparable with the MDLs of the published literature reports. Therefore, the proposed MW-AE method can be routinely used for monitoring of metal ions in various river and fresh water sediments.     

New human hair certified reference material for methylmercury and trace elements

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1, 000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.     

New human hair certified reference material for methylmercury and trace elements

 A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given. Received: 8 February 1996/Accepted: 4 April 1996     

Development of a certified reference material (NMIJ CRM 7505-a) for the determination of trace elements in tea leaves

A certified reference material (CRM) for trace elements in tea leaves has been developed in National Metrology Institute of Japan (NMIJ). The CRM was provided as a dry powder (<90 μm) after frozen pulverization of washed and dried fresh tea leaves from a tea plant farm in Shizuoka Prefecture, Japan. Characterization of the property value for each element was carried out exclusively by NMIJ with at least two independent analytical methods, including inductively coupled plasma mass spectrometry (ICP-MS), high-resolution (HR-) ICP-MS, isotope-dilution (ID-) ICP-MS, inductively coupled plasma optical emission spectrometry (ICP-OES), graphite-furnace atomic-absorption spectrometry (GF-AAS) and flame atomic-absorption spectrometry (FAAS). Property values were provided for 19 elements (Ca, K, Mg, P, Al, B, Ba, Cd, Cu, Fe, Li, Mn, Na, Ni, Pb, Rb, Sr, Zn and Co) and informative values for 18 elements (Ti, V, Cr, Y, and all of the lanthanides, except for Pm whose isotopes are exclusively radioactive). The concentration ranges of property values and informative values were from 1.59% (mass) of K to 0.0139 mg kg(-1) of Cd and from 0.6 mg kg(-1) of Ti to 0.0014 mg kg(-1) of Lu, respectively. Combined relatively standard uncertainties of the property values were estimated by considering the uncertainties of the homogeneity, analytical methods, characterization, calibration standard, and dry-mass correction factor. The range of the relative combined standard uncertainties was from 1.5% of Mg and K to 4.1% of Cd.     

A pilot study for the production of a certified reference material for trace elements in honey

In the context of the general mandate of the European Union Community Reference Laboratory (CRL) for residues in living animals and their products established at the Istituto Superiore di Sanità, a pilot study was undertaken to assess the possibility of producing a new certified reference material (CRM) for trace elements in a matrix of honey. The elements considered were As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sn, V and Zn. Their determination was performed by inductively coupled plasma (ICP)-based techniques. Data obtained with different ICP techniques were generally in good agreement. In light of these results, the next step was the effective production of a candidate CRM in a honey matrix. In the preliminary phase, two different types of honey, i.e., Eucalyptus (solid and sticky) and Robinia (viscous and sticky), were pretreated at the Institute for Reference Materials and Measurements, Joint Research Centre, European Commission (EC-JRC-IRMM) in order to produce the materials candidate for the certification process. Approximately 600 ampoules were thus produced for the Robinia honey and 450 ampoules for the Eucalyptus honey, each ampoule containing 5 g of an aqueous solution of honey (with 20% and 30% high purity water, respectively) and sealed under inert gas (Ar). A ring test to determine the levels of the chemical elements and a long-term study to evaluate the stability of the samples is in progress. Tentative figures for the analytes of interest are (in ng g⁻¹): Robinia, As, 1.28±0.09; Cd, 0.59±0.08; Cr, 2.36±0.21; Cu, 57.6±3.2; Fe, 209±9; Mn, 90.8±3; Ni, 18.1±0.6; Pb, 23±1.5; Sn, 8.10±0.35; V, 1.19±0.37; and Zn, 178±4; Eucalyptus, As, 3.18±0.21; Cd, 0.70±0.08; Cr, 2.73±0.22; Cu, 141±6; Fe, 926±16; Mn, 1905±81; Ni, 7.77±0.4; Pb, 138±4; Sn, 7.97±0.16; V, 3.47±0.15; and Zn, 405±9.     

Characterization of certified reference material for quantification of polychlorinated biphenyls and organochlorine pesticides in fish

Fish certified reference material (CRM), NMIJ CRM 7404-a, for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) was developed by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Fish samples (Japanese seabass) used for the preparation of the CRM were collected from Tokyo Bay, and the edible part was freeze-dried, pulverized, sieved, homogenized, and sterilized by γ-irradiation. This sample is in the form of a powder comprising approximately 10 g stored in a brown glass bottle. The certification was carried out using multiple analytical methods such as pressurized liquid extraction, Soxhlet extraction, saponification, and homogenization to ensure the reliability of analytical results; the certified values of target PCBs (PCB 28, PCB 70, PCB 105, PCB 153, and PCB 170) and OCPs (trans-nonachlor, dieldrin, p,p′-DDE, p,p′-DDT, and p,p′-DDD) were 1.05–14.0 μg kg⁻¹ and 1.57–18.0 μg kg⁻¹ for PCBs and OCPs, respectively. This is the first fish powder CRM in which PCBs and OCPs were determined by isotope dilution mass spectrometry.     

A mussel tissue certified reference material for multiple phycotoxins. Part 3: homogeneity and stability

A candidate certified reference material (CRM) for multiple shellfish toxins (domoic acid, okadaic acid and dinophysistoxins, pectenotoxins, yessotoxin, azaspiracids and spirolides) has been prepared as a freeze-dried powder from mussel tissues (Mytilus edulis). Along with the certified values, the most important characteristics for a reference material to be fit-for-purpose are homogeneity and stability. Acceptable between-bottle homogeneity was found for this CRM. Within-bottle homogeneity was assessed using domoic acid, and it was shown that repeated subsampling of the CRM can be performed precisely down to 0.35 g. Both short- and long-term stability studies carried out under isochronous conditions demonstrated excellent stability of the various toxins present in the material. While degradation of some analytes was observed at +60°C in short-term studies, it was determined that shipping at ambient temperature is adequate. No instability was detected in long-term stability studies, and it was shown that the material can be held at +18°C safely for up to 1 year. To guarantee stability of the CRM over its lifetime the stock will be maintained at −20°C. The results of the homogeneity and stability testing show that CRM–FDMT1 is appropriate for its intended use in quality assurance and quality control of shellfish toxin analysis methods.     

A mussel tissue certified reference material for multiple phycotoxins. Part 1: design and preparation

The development of multi-analyte methods for lipophilic shellfish toxins based on liquid chromatography–mass spectrometry permits rapid screening and analysis of samples for a wide variety of toxins in a single run. Validated methods and appropriate certified reference materials (CRMs) are required to ensure accuracy of results. CRMs are essential for accurate instrument calibration, for assessing the complete analytical method from sample extraction to data analysis and for verifying trueness. However, CRMs have hitherto only been available for single toxin groups. Production of a CRM containing six major toxin groups was achieved through an international collaboration. Preparation of this material, CRM-FDMT1, drew on information from earlier studies as well as improved methods for isolation of toxins, handling bulk tissues and production of reference materials. Previous investigations of stabilisation techniques indicated freeze-drying to be a suitable procedure for preparation of shellfish toxin reference materials and applicable to a wide range of toxins. CRM-FDMT1 was initially prepared as a bulk wet tissue homogenate containing domoic acid, okadaic acid, dinophysistoxins, azaspiracids, pectenotoxin-2, yessotoxin and 13-desmethylspirolide C. The homogenate was then freeze-dried, milled and bottled in aliquots suitable for distribution and analysis. The moisture content and particle size distribution were measured, and determined to be appropriate. A preliminary toxin analysis of the final material showed a comprehensive toxin profile.     

Cabbage leaves CL-1 certified reference material for the trace analysis of plant materials

Summary The preparation of cabbage leaves (CL-1) certified reference material and homogenisation procedures are described and relevant data are compiled. In evaluation of the data four concurrent tests (Dixon's, Grubb's, Nalimov's and the test of coefficient of Kurtosis) for outlier rejection at the significance level 0.05 have been applied. As a result it was possible to establish certified concentration values for 10 elements and reference values for 4 elements.

---

Zertifiziertes Referenzmaterial Cabbage Leaves CL-1 für die Spurenanalyse von pflanzlichem Material