Summary of preparation and homogeneity characterization of ten agricultural food reference materials for elemental composition

Summary Preparation and development has been completed of ten agricultural/food reference materials (RMs): bovine muscle powder, corn starch, hard red spring wheat flour, soft winter wheat flour, whole milk powder, wheat gluten, corn bran, durum wheat flour, whole egg powder and microcrystalline cellulose. Homogeneity tests for 14 elements, Al, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were performed by the initiating laboratories by application of precise and reliable analytical methods based on flame atomic absorption spectrometry and graphite furnace atomic absorption spectrometry. An extensive set of analytical results obtained from the interlaboratory cooperative characterization campaign was assessed to provide homogeneity estimates for other elements. Estimates of homogeneity from within-laboratory precision indicated that all materials exhibited acceptable homogeneity for virtually all 29 elements (Al, As, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Se, Sr, V, Zn) for which best estimate concentration values are available. Two thirds of all homogeneity coefficients of variation were below 5%.     

Preliminary assessment of homogeneity of new candidate agricultural/food reference materials

Summary In an effort to bring to the analytical community new natural matrix reference materials (RM's) for elemental composition quality control, ten new agricultural/food candidate reference materials prepared previously, were characterized for homogeneity. The materials include bovine muscle powder, whole egg powder, corn bran, microcrystalline cellulose, wheat gluten, whole milk powder, corn starch and three wheat flours representing a wide range of matrix types and elemental composition. Characterization was for up to some twenty five major, minor, trace and ultratrace elements of nutritional, toxicological and environmental significance. Solid sampling electrothermal atomic absorption spectrometry was applied to the determination of copper and lead in sub-milligram subsamples. A variety of other analytical techniques via an interlaboratory cooperative effort was used to determine many other elements in 100–2000 mg subsample sizes. Good material homogeneity was observed for virtually all materials and analytes with the exception of Cr and Pb in limited instances. The materials were thus deemed suitable for detailed characterization of elemental concentration to lead to recommended values and to bring these biological products to reference material status.     

An interlaboratory characterization (certification) campaign to establish the elemental composition of a new series of agricultural/food reference materials

Summary Ten new Agricultural/Food Reference Materials (RM) have been characterized with respect to their elemental compositions in an extensive interlaboratory characterization (certification) campaign. The philosophy applied to determine best estimate and informational concentration values was the expert analyst-independent method approach. Chemical analyses were conducted in two initiating laboratories and by analysts in 73 cooperating laboratories applying 13 major classes of independently different analytical methods; approximately 13,000 results were obtained for a large number of nutritionally, toxicologically and environmentally pertinent elements. Results were assessed in depth using technical judgment and statistical criteria. A total of 213 best estimate values, with associated uncertainties for a single future observation, and 65 informational values were obtained. Concentrations were measured for 34 elements in 10 materials which represent a wide range of matrices and elemental contents and significantly augment the world repertoire of reference materials.Contribution no. 92–214 from Centre for Land and Biological Resources Research     

Summary of an interlaboratory characterization (certification) campaign to establish the elemental composition of a new series of agricultural/food reference materials

Summary Ten new Agricultural/Food Reference Materials (RMs) were characterized with respect to their elemental compositions via an interlaboratory characterization (certification) campaign. Chemical analyses were conducted in 73 cooperating laboratories applying 13 major classes of independently different analytical methods. A total of 213 best estimate values, and 65 informational values were obtained for Al, As, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Ti, V, W and Zn in the following RMs: Bovine Muscle Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415), Microcrystalline Cellulose (NIST RM 8416), Wheat Gluten (NIST RM 8418), Corn Starch (NIST RM 8432), Corn Bran (NIST RM 8433), Whole Milk Powder (NIST RM 8435), Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437) and Soft Winter Wheat Flour (NIST RM 8438).     

Reference materials for agricultural and food analysis: Preparation and physical characterization of a bovine muscle powder candidate reference material

Summary The most cost-effective way of monitoring and maintaining reliability of an analytical procedure is by the incorporation of appropriate, compositionally-similar reference materials into the scheme of analysis. Agricultural and food commodities represent an extremely wide range of composition in respect of both the sought-for analyte and the remainder of the supporting material (matrix) which are not reflected in currently-available biological reference materials (BRMs). In an attempt to fill some of these gaps in the world repertoire of reference materials, cooperative work is underway to prepare and characterize a number of materials for data quality control for inorganic constituents. The first two products of this venture, Maize Stalk and Maize Kernel Reference Materials 8412 and 8413, respectively, with recommended concentrations for eleven elements are available from USNBS. A third product, a powdered Bovine Muscle candidate reference material has been prepared in quantity. Meat from beef cattle (Bos Taurus) comprising muscles commonly-denoted round steak was trimmed, ground, freeze-dried, -ray sterilized, ball milled, sieved, blended and packaged. The final product was a finely powdered, visually uniform material consisting of muscle fibers with over 70% of the particles with radius of an equivalent sphere in the range 10–40 m (median 25 m).Efforts are underway to develop a number of other BRMs representative of the large number of important food classes. Cooperative work with expert analytical laboratories is anticipated to lead to characterization of the Bovine Muscle candidate reference material and the other materials in respect of concentrations of a large number of nutritionally, toxicologically and environmentally-important major, minor and trace chemical elements as well as proximate constituents such as protein, fibre, fat and ash.Contribution No. 86-68 from Land Resource Research Centre     

Preparation of twelve candidate agricultural reference materials

Summary A cost-effective approach to monitoring and maintaining reliability of analytical procedures is by the incorporation of appropriate, compositionally similar reference materials into the scheme of analysis. Agricultural and food commodities represent an extremely wide range of composition, in respect of the sought-for analyte and the supporting material (matrix), not fully reflected in currently available biological reference materials (BRM's). With the view to attempting to fill some of the gaps in the world repertoire of reference materials and to have suitable products for our laboratories' use, preparation has been completed of twelve candidate agricultural reference materials. These products, representing a number of food classes, include bovine muscle powder, hard red spring wheat flour, soft winter wheat flour, durum wheat flour, wheat gluten, corn bran, corn starch, potato starch, whole egg powder, whole milk powder, microcrystalline cellulose, and sugar. Preparative steps included, as required, freeze drying, grinding or ball milling, X-ray sterilization, sieving, blending and packaging to yield sizeable quantities of each material in finely powdered form. Cooperative analytical effort is expected to lead to characterization in respect of concentrations of a number of nutritionally, toxicologically and environmentally-pertinent, major, minor, and trace chemical elements. These materials will then be available for analytical chemical data quality control for inorganic constituents in a range of agricultural commodities.

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Herstellung von zwölf als landwirtschaftliche Referenzmaterialien vorgeschlagenen Substanzen

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Contribution No. 88-49 from Land Resource Research Centre     

Preparation and testing for homogeneity of spiked strawberry and cabbage candidate reference materials

Strawberry and cabbage candidate reference materials (RMs) have been prepared by our laboratory during 1992–1993. Fresh materials have been homogenized and spiked with known concentrations of pesticides representing compounds commonly used for strawberries and cabbages. The candidate RMs have been then freeze-dried, homogenized, bottled under a stream of nitrogen and stored frozen at –20°C. Homogeneity and stability of the candidate RMs have been studied during the storage period. Homogeneity of the candidate RMs for 5 g samples has been within 10%. Homogeneity and stability studies have been carried out using the conventional multiresidue method of Luke et al. [1]. Instrumental analysis have been performed by gas chromatography mass spectrometry (GC-MS) employing selected ion monitoring (SIM).     

BCR reference materials for food and agricultural analysis: an overview

Summary The BCR is a research programme of the European Communities having the broad aim of improving accuracy and measurement harmony in areas of concern at Community level. Much of the work is directly relevant to the removal of trading and other obstacles as is necessary for the achievement of a single European market by 1992.The presentation provides an overview of the sector of the programme concerned with Reference Materials (RMs) for food and agricultural analyses.Summarises are given of activities for inorganic, trace organic and nutritional analyses, for calibration of rapid methods (NMR, NIR, XRF and Immuno-assay techniques) and technological measurements (industrial quality of cereals, food colour, water-sorption and detection of fraudulent addition of sugar during wine making by NMR). An alphabetic listing of analytes and properties studied during the programme is given.

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BCR-Referenzmaterialien für die Lebensmittel- und landwirtschaftliche Analyse — Ein Überblick

     

Oxygen isotope homogeneity assessment for apatite U-Th-Pb geochronology reference materials

Secondary ion mass spectrometry (SIMS) measurement of oxygen isotopes in apatite has been employed more and more in petrogenetic, metallogenic, and climate change studies. Well-characterised reference materials are needed due to the matrix effect, but they are yet to be well established. In this study, we conducted in-situ oxygen isotopic and chemical analyses on six commonly used apatite reference materials (ie, Emerald, Kovdor, McClure, Mud Tank, Otter Lake, and Slyudyanka) and two in-house apatite references (Qinghu and GEMS 203) to assess their oxygen isotope homogeneity and applicability for microbeam analyses. Our results show that all these apatite references are in general chemically homogeneous. In terms of oxygen isotopes, GEMS 203 (δ¹⁸O = 9.85 ± 0.40‰ [2SD], corrected by Durango 3), Kovdor (δ¹⁸O = 6.55 ± 0.38‰, 2SD), and McClure (δ¹⁸O = 5.94 ± 0.42‰, 2SD) are fairly homogeneous, whereas Emerald (δ¹⁸O = 10.37 ± 0.45‰, 2SD), Mud Tank (δ¹⁸O = 6.35 ± 0.46‰, 2SD), Otter Lake (δ¹⁸O = 9.71 ± 0.47‰, 2SD), Qinghu (δ¹⁸O = 5.44 ± 0.49‰, 2SD), and Slyudyanka (δ¹⁸O = 17.49 ± 0.43‰, 2SD) are less homogenous. This indicates that the former group represents better reference materials for in-situ oxygen isotopic analyses, whilst the latter group can be used as secondary reference material for analytical quality control.     

Preparation and characterization of a suite of ephedra-containing standard reference materials

The National Institute of Standards and Technology, the U.S. Food and Drug Administration, Center for Drug Evaluation and Research and Center for Food Safety and Applied Nutrition, and the National Institutes of Health, Office of Dietary Supplements, are collaborating to produce a series of Standard Reference Materials (SRMs) for dietary supplements. A suite of ephedra materials is the first in the series, and this paper describes the acquisition, preparation, and value assignment of these materials: SRMs 3240 Ephedra sinica Stapf Aerial Parts, 3241 E. sinica Stapf Native Extract, 3242 E. sinica Stapf Commercial Extract, 3243 Ephedra-Containing Solid Oral Dosage Form, and 3244 Ephedra-Containing Protein Powder. Values are assigned for ephedrine alkaloids and toxic elements in all 5 materials. Values are assigned for other analytes (e.g., caffeine, nutrient elements, proximates, etc.) in some of the materials, as appropriate. Materials in this suite of SRMs are intended for use as primary control materials when values are assigned to in-house (secondary) control materials and for validation of analytical methods for the measurement of alkaloids, toxic elements, and, in the case of SRM 3244, nutrients in similar materials.     

The synthesis and characterization of pure substance reference materials for forensic, agricultural and drugs-in-sport analysis

 The paper reports work on the synthesis, purification and certification of pure substance (organic) reference materials as conducted within the National Analytical Reference Laboratory (NARL). Areas of interest include illicit drugs, agricultural and veterinary chemicals, and steroids and steroid metabolites and their deuterates. The discussion covers the prioritization of work requirements, procedures for synthesis and production, quality assurance, characterization, homogeneity, storage and stability testing, and certification of materials. Future plans for establishing traceability are also discussed.     

Reference materials and certified reference materials for water and food microbiology

Summary The concept of Certified Reference Materials (CRMs) for the verification of the accuracy of analytical methods and the traceability of the results to a CRM, is well accepted in chemistry. The use of Reference Materials (RMs) for intra-laboratory quality control schemes or for round-robin and proficiency testing is well established and follows from certain norms (ISO 9000 and EN 45000 series). For microbiology such concepts have not been fully defined and RMs are only rarely used. CRMs do not exist. To fill this gap the Commission of the European Community, through the BCR programme, has launched projects in collaboration with the RIVM (National Institute of Public Health and Environmental Protection) in Bilthoven (NL). Following fundamental considerations and feasibility studies, several intercomparisons have been held using selected laboratories working with food or water microbiology. Various microbiological strains have been subject of studies: Salmonella typhimurium, Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus for food, Escherichia coli, Enterococcus faecium, Enterobacter cloacae and Staphylococcus warneri for water. To produce materials for interlaboratory studies, a set of milk powders was prepared by spray-drying. Separate portions were contaminated with one of the strains mentioned. The materials were then encapsuled in gelatine. It has been demonstrated that if protected in milk powder matrices, bacteria maintain the ability to be revived, but do not multiply. The modes of evaluation of the results for homogeneity and stability differ from those commonly used in chemistry.     

Need for food reference materials in Asia

Summary A survey was conducted to determine perception, knowledge, use or application of Food Reference Materials (Food RM) in Asia and to assess individual country needs for these materials. Respondents of the questionnaire came from government institutions, private laboratories, food industries and state universities in 12 countries in Asia involved in food composition data generation. Results showed that only a third of the respondents had been using Food RM in their studies while the remainder were either unaware or not using these materials for logistical reasons or unavailability. The survey revealed emerging interest on the need to establish a Food RM Program in Asia. A common implementation strategy expressed by respondents is the creation of a center, where Food RM can be developed. This center will also be entrusted with the distribution of Food RM and collection, monitoring and evaluation of analytical data. The survey results will help ASIAFOODS in formulating guidelines or planning action regarding the use of Food RM to ensure accurate and dependable food composition data in the Asian region.     

Development of food reference materials for nutritional analysis

Summary The development of five reference materials for major nutritional properties, whole milk powder, pork muscle, wheat and rye flour, and haricots verts beans is described. Homogeneity and stability of these materials proved to be adequate. A preliminary intercomparison of methods showed that results for total fat and total dietary fibre were method dependent. Evaluation of methods used for available carbohydrates revealed poor solubilisation and hydrolysis of starch in some laboratories. This intercomparison has given valuable information for the final certification of these materials.     

Evaluation of sample homogeneity for geochemical standard reference materials used in microanalysis

Three proposed National Bureau of Standards clay standard reference materials, flint clay SRM 97b, plastic clay, SRM 98b, and brick, SRM 679 were investigated for homogeneity with respect to their contents of Sm, La, Sc, Th, Hf, As, Ga, Fe and Cr. Sub-samples were analyzed by instrumental neutron activation analysis (INAA) and replicate determinations were made on nominal sample weights of 100, 400, 750, and 1000 g. For Sm, La, Sc and Th, no increase in the relative standard deviation with decreasing sample weight was observed in all SRMs indicating that subsampling error for these elements was not a large component of the overall error. For Ga in all SRMs and Cr, As and Fe in SRM 98b, an increase in the relative standard deviation with decreasing sample weight suggests that these elements are concentrated in a minor component of the sample. The three clays should be good reference materials for trace element microanalysis for the elements investigated.     

Assessment of element-specific homogeneity in reference materials using microanalytical techniques

The IAEA established in 1994 a co-ordinated research programme (CRP) on "Reference Materials for Microanalytical Nuclear Techniques" as part of its efforts to promote and strengthen the use of nuclear analytical technologies in member states with the specific aim of improving the quality of analysis of nuclear, environmental, and biological materials. The objectives of this initiative were: to identify suitable biological reference materials which could serve the needs for quality control in microanalytical techniques; to evaluate existing CRMs for use in microanalytical investigations; to evaluate appropriate sample pretreatment procedures for materials being used for analysis with microanalytical techniques; to identify analytical techniques which can be used for characterisation of homogeneity determination, and to apply such techniques to the characterization of candidate reference materials for use with microanalytical techniques. The CRP lasted for 4 years and seven laboratories and the Agency's Laboratories in Seibersdorf participated. A number of materials including the candidate reference materials IAEA 338 (lichen) and IAEA 413 (single cell algae, elevated level) were evaluated for the distribution of elements such as Cl, K, Ca, Cr, Mn, Fe, Zn, As, Br, Rb, Cd, Hg, and Pb. The results obtained during this CRP suggest that: each element exhibits its characteristic distribution in a matrix described by the "Ingamels' sampling constant" or the "relative homogeneity factor" of Kurfuerst; both concepts are valid over a large range of sample mass used for analysis (from 0.1 g to around 100 mg); and materials being characterised quantitatively for element homogeneity could be used for the experimental determination of total uncertainty of other analytical techniques. As far as we are aware this is the first time the concept of quantitative characterisation of homogeneity has been applied to potential reference materials and the first demonstration of the feasibility and usefulness of the concept with particular emphasis on enhancing quality control opportunities for microanalytical techniques.     

Preparation and characterization of PAA/ GG-zeolite nano-composite hydrogel for agricultural applications

The worldwide water crisis has become adverse in recent times, affecting water usage in various fields, including industries, agriculture, and domestic. This research aims to produce a nano-composite hydrogel based on natural materials using zeolite and guar gum (Zeolite-GG). For the development of PAA/GG-Zeolite nano-composite hydrogel (PGZ nano-composite hydrogel), acrylic acid (AA) act as monomer, polyethylene glycol (PEG-600) act as a crosslinker and potassium persulfate (KPS) used as the initiator. The developed nano-composite material has been characterised using numerous tests such as, Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), scanning electron microscope (SEM) and Energy Dispersive X-Ray (EDX). The size range from 30.76 to 62.01 nm is found in SEM analysis. The Transmission Electron Microscopy (TEM) analysis confirms that the material consists of a spherical shape with a size range of 56.40 nm–82.70 nm.Moreover, the EDX test confirms the existence of Potassium (60.20%), Carbon (20.03%), and Oxygen (19.76%) in the synthesized material. Furthermore, the presence of material functional groups and thermal stability was verified using FTIR and TGA, respectively. The swelling index of developed hydrogel is found to be 92.50 mL per gram. The synthesized PGZ Nano-composite hydrogel has enough potential to act as a nutrient carrier and soil conditioning agent in agriculture, especially in the arid and semi-arid regions, due to its higher Potassium (K) content and high water absorption capacity.     

Primary reference materials and traceability chain for gas composition

This article briefly describes research on the development of primary reference gases and the traceability system of gas measurement at the National Research Center for Certified Reference Materials, China.