Investigations on the water content of candidate reference material CRM 679 cabbage powder

The determination of the residual water content by thermal methods and especially by Karl Fischer titration in a candidate reference material of the European Commission (candidate CRM 679 cabbage powder) is described and discussed.     

Investigations on the water content of candidate reference material CRM 679 cabbage powder

The determination of the residual water content by thermal methods and especially by Karl Fischer titration in a candidate reference material of the European Commission (candidate CRM 679 cabbage powder) is described and discussed.     

Development of reference materials for the analysis of acid-extractable metals in sludge

The development of reference materials to verify the determination of metals in sludge is described. Effluents from domestic and industrial treatment facilities were dried, size-reduced and homogenized. Multiple aliquots of each material were analyzed in two different government laboratories to determine reference values for the acid-extractable concentrations of more than 15 metals. These acid-extractable concentrations are distinct from total metal values. Different sample preparation and instrumental methods, along with internal quality assurance protocols, were used to confirm the results. The data show good agreement for most metals in the domestic material. Reference values for the leachable concentrations of several toxic metals and major constituents will become part of the Certificate of Analysis for Standard Reference Material (SRM) 2781 issued by the National Institute of Standards and Technology (NIST). Data for the candidate industrial sludge reference material are also presented and discussed.     

Characterization of NIES CRM No. 23 Tea Leaves II for the determination of multielements

A candidate environmental certified reference material (CRM) for the determination of multielements in tea leaves and materials of similar matrix, NIES CRM No. 23 Tea Leaves II, has been developed and characterized by the National Institute for Environmental Studies (NIES), Japan. The origin of the material was tea leaves, which were ground, sieved through a 106-μm mesh, homogenized, and then subdivided into amber glass bottles. The results of homogeneity and stability tests indicated that the material was sufficiently homogeneous and stable for use as a reference material. The property values of the material were statistically determined based on chemical analyses by a network of laboratories using a wide range of methods. Sixteen laboratories participated in the characterization, and nine certified values and five reference values were obtained. These property values of the candidate CRM, which are expressed as mass fractions, were close to the median and/or mean values of the mass fractions of elements in various tea products. The candidate CRM is appropriate for use in analytical quality control and in the evaluation of methods used in the analysis of tea and materials of similar matrix.     

Use of INAA in the homogeneity evaluation of a bovine kidney candidate reference material

Instrumental neutron activation analysis was used to evaluate the between bottle homogeneity and the minimum sample intake of a bovine kidney candidate reference material. The mass fractions of ten inorganic constituents were determined, obtaining satisfactory homogeneity results for all of them. Statistical analysis of the results was performed using a one way analysis of variance and multivariate techniques were applied as complementary techniques, confirming the usefulness of these techniques for homogeneity assessment.

     

River sediment (S-37)--a new analytical quality control material ensuring comparability of chlorinated hydrocarbon analysis during an international environmental study in China

A sediment reference material (S-37) was prepared as analytical quality control material to be used within an international project on polychlorinated hydrocarbon analysis in two Chinese rivers. The raw material was sampled during a cruise on Yangtse River and transported afterwards to the JRC Ispra for further processing. The material was treated according to the general principles applicable for candidate reference material production. After a thorough homogeneity study of the bulk the material was bottled. A total of 1,080 bottles each containing 50 g of dry sediment powder was obtained. Final homogeneity and stability testing proved the material to be fit for the purpose. Isotope dilution GC/MS was used to establish target values for pentachlorobenzene (1.17 +/- 0.08 ng/g), hexachlorobenzene (3.60 +/- 0.17 ng/g), octachlorostyrene (0.19 +/- 0.01 ng/g), pentachloroanisole (0.52 +/- 0.02 ng/g), alpha-HCH (0.70 +/- 0.05 ng/g), beta-HCH (1.38 +/- 0.18 ng/g), gamma-HCH (0.83 +/- 038 ng/g), 2,4'-DDT (0.36 +/- 0.04 ng/g), 2,4'-DDE (0.29 +/- 0.02 ng/g), 2,4'-DDD (0.49 +/- 0.02), 4,4'-DDT (3.42 +/- 0.47 ng/g), 4,4'-DDD (1.29 +/- 0.17 ng/g), PCB 28 (0.11 +/- 0.01 ng/g), PCB 52 (0.09 +/- 0.003 ng/g), PCB 101 (0.07 +/- 0.003 ng/g), PCB 138 (0.06 +/- 0.003 ng/g) and PCB 153 (0.06 +/- 0.003 ng/g). Furthermore, indicative values for major and minor constituents as well as for polychlorinated dibenzodioxines and -furanes were measured.     

白菜汁中3种酰胺类除草剂候选标准样品的制备与定值方法研究

向浓缩白菜汁中添加乙草胺、丁草胺、甲草胺3种酰胺类除草剂的混和标准溶液,搅拌均匀并分装后对其进行均匀性检验,在-18℃冷冻保存下进行稳定性检验。经F检验结果表明,研制的候选标准样品均匀性良好;通过直线模型验证标准样品的稳定性,结果表明在冷冻保存条件下,标准样品中除草剂含量在半年内是稳定的。对研制的标准样品进行了定值,并对定值结果的不确定度进行了评定。     

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     

River sediment (S-37) – A new analytical quality control material ensuring comparability of chlorinated hydrocarbon analysis during an international environmental study in China

A sediment reference material (S-37) was prepared as analytical quality control material to be used within an international project on polychlorinated hydrocarbon analysis in two Chinese rivers. The raw material was sampled during a cruise on Yangtse River and transported afterwards to the JRC Ispra for further processing. The material was treated according to the general principles applicable for candidate reference material production. After a thorough homogeneity study of the bulk the material was bottled. A total of 1080 bottles each containing 50 g of dry sediment powder was obtained. Final homogeneity and stability testing proved the material to be fit for the purpose. Isotope dilution GC/MS was used to establish target values for pentachlorobenzene (1.17 ± 0.08 ng/g), hexachlorobenzene (3.60 ± 0.17 ng/g), octachlorostyrene (0.19 ± 0.01 ng/g), pentachloroanisole (0.52 ± 0.02 ng/g), α-HCH (0.70 ± 0.05 ng/g), β-HCH (1.38 ± 0.18 ng/g), γ-HCH (0.83 ± 038 ng/g), 2,4′-DDT (0.36 ± 0.04 ng/g), 2,4′-DDE (0.29 ± 0.02 ng/g), 2,4′-DDD (0.49 ± 0.02), 4,4′-DDT (3.42 ± 0.47 ng/g), 4,4′-DDD (1.29 ± 0.17 ng/g), PCB 28 (0.11 ± 0.01 ng/g), PCB 52 (0.09 ± 0.003 ng/g), PCB 101 (0.07 ± 0.003 ng/g), PCB 138 (0.06 ± 0.003 ng/g) and PCB 153 (0.06 ± 0.003 ng/g). Furthermore, indicative values for major and minor constituents as well as for polychlorinated dibenzodioxines and -furanes were measured.     

聚甲基丙烯酸甲酯锥形量热仪标准物质候选物的均匀性和稳定性考察

介绍聚甲基丙烯酸甲酯锥形量热仪标准物质候选物的制备过程,对其配方设计、制备工艺、均匀性检验、稳定性考察进行了研究。采用锥形量热仪研究了炭黑的种类、炭黑的添加量、聚甲基丙烯酸甲酯的熔融指数对标准物质候选物热释放速率的影响。当添加质量分数0.5%的炭黑于熔融指数为16.0 g/(10 min)的聚甲基丙烯酸甲酯中时,该标准物质候选物具有良好的均匀性和稳定性。     

Long-term stability study on a Perna perna mussel candidate reference material

The long-term stability study, one of the steps in the characterization of new reference materials, is performed on freeze-dried biological reference materials to verify if they may be stored at room temperature without modification of the property values of interest. In this study, instrumental neutron activation analysis was used in a 12-month long isochronous long-term stability study performed on a Perna perna mussel candidate reference material. No trend in the results was observed in respect to measurement order and exposition period to room temperature. The assessment of the analysis of variance test as well as the normalized results to the control temperature showed no systematic changes in the mass fractions of Ag, As, Br, Co, Cr, Cs, Fe, Eu, La, Na, Rb, Sc, Se, Th and Zn during the test period. The result showed that the candidate reference material may be stored at room temperature without significant changes in composition for the determined elements.     

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).     

The certification of SRM 1546--Meat Homogenate, a new reference material for nutrients in a high protein, high fat matrix

In response to reference material needs expressed by the food industry and government regulators, the National Institute of Standards and Technology (NIST) has developed a new Standard Reference Material (SRM) consisting of a canned meat product with certified and reference values for a large number of constituents. SRM 1546 Meat Homogenate consists of a mixture of finely ground pork and chicken prepared and canned by a commercial process. NIST determined the concentration levels of cholesterol, sodium, calcium, iron, and seven fatty acids in this SRM using well defined methods and procedures. These analytes as well as 34 other constituents or properties were determined in an interlaboratory comparison exercise involving 21 laboratories, most of which are associated with the National Food Processors Association (NFPA) Food Industry Analytical Chemists Subcommittee (FIACS). From statistical analysis of the data, NIST assigned certified concentrations for the eleven analytes measured at NIST and reference concentrations for the proximates, six additional fatty acids, seven minerals, and seven water-soluble vitamins. Information values without uncertainties are provided for the concentrations of six additional constituents for which the uncertainties could not adequately be assessed. SRM 1546 will provide laboratories with a means to evaluate the accuracy of the methods they use to assign nutrient levels to processed meats and similar products.     

The interpretation and use of stability data in the certification of reference materials

 Stability tests are carried out on candidate reference materials in order to ascertain that the certification values continue to be valid a reasonable time after completion of the certification analysis. These tests are also used for recommending storage conditions, as well as the duration of storage before certification values need be rechecked. BCR (Community Bureau of Reference) reference materials do not normally have an expiry date, but rely on stability monitoring throughout the lifetime of the certified material. The 1997 version of the BCR Guidelines for the production and certification of reference materials does, however, take into account the necessity of limiting the validity of a certification, when degradation of the material during storage cannot be ignored. This paper discusses an example of significant degradation taking place between the time of completion of the certification analysis and the issue of a formal certificate. Various options are presented together with an account of their influence on the certified values and their uncertainties. Received: 3 October 1997 · Accepted: 3 November 1997     

Mixed diet reference materials for nutrient analysis of foods: Preparation of SRM-1548 Total Diet

Summary Several mixed component diet materials have been available for use as reference materials for determination of elemental contents in food. These included H-9, issued by the IAEA and RM-8431, issued by NIST. Wide acceptance of these materials has exhausted supplies and they are no longer available. A new mixed food Standard Reference Material, SRM-1548 Total Diet, has been prepared and characterized for a number of elemental and organic constituents. This material was prepared from foods obtained from collections of the US FDA's Total Diet Study, which are representative of foods consumed by the US population. SRM-1548 has been composited from these foods, in proportions that are representative of daily intake. The composited foods were blended, freeze-dried, reblended and bottled in portions of 6 g. Homogeneity studies were carried out along with certification analyses for elements, cholesterol proximate and caloric content. This material is available from NIST and will be useful as a multi-purpose SRM for determinations of constituents in the naturally occurring range in foods and food related materials. Since this is a mixture of foods of both good and poorer sources, levels will be at the lower end of the concentration range for any individual constituent. Availability of further SRM's of individual foods with higher levels of specific constituents, such as SRM-1845 Cholesterol in Whole Egg will be required to extend the range of certified concentration values for food reference materials.     

The certification of SRM 1546 – Meat Homogenate, a new reference material for nutrients in a high protein, high fat matrix

In response to reference material needs expressed by the food industry and government regulators, the National Institute of Standards and Technology (NIST) has developed a new Standard Reference Material (SRM) consisting of a canned meat product with certified and reference values for a large number of constituents. SRM 1546 Meat Homogenate consists of a mixture of finely ground pork and chicken prepared and canned by a commercial process. NIST determined the concentration levels of cholesterol, sodium, calcium, iron, and seven fatty acids in this SRM using well defined methods and procedures. These analytes as well as 34 other constituents or properties were determined in an interlaboratory comparison exercise involving 21 laboratories, most of which are associated with the National Food Processors Association (NFPA) Food Industry Analytical Chemists Subcommittee (FIACS). From statistical analysis of the data, NIST assigned certified concentrations for the eleven analytes measured at NIST and reference concentrations for the proximates, six additional fatty acids, seven minerals, and seven water-soluble vitamins. Information values without uncertainties are provided for the concentrations of six additional constituents for which the uncertainties could not adequately be assessed. SRM 1546 will provide laboratories with a means to evaluate the accuracy of the methods they use to assign nutrient levels to processed meats and similar products. Received: 11 October 2000 / Revised: 15 December 2000 / Accepted: 21 December 2000     

Element concentrations in candidate biological and environmental reference materials by ko-standardized INAA

Summary k_o-Based Neutron Activation Analysis (k_oINAA) was used to analyze the candidate reference materials Apple Leaves and Peach Leaves, and Oriental Tobacco Leaves and Virginia Tobacco Leaves. Concentration values for 27 elements were measured. The accuracy was ascertained by analysis of two certified reference materials, NIST 1572 Citrus Leaves and 1573 Tomato Leaves. The homogeneity test of the IAEA Evernia prunastri candidate reference material in aliquots 100 mg is extended to the elements Sc, Cr, Fe, Co, Zn, Rb, Sb, Cs, Ba, Ce and Th.     

Preparation and characterization for mineral elements and total dietary fiber and testing for stability of β-carotene of an ARC/CL carrot powder multipurpose candidate reference material

As part of the analytical assurance system of the FAO European Cooperative Research Network on Trace Elements programme an ARC/CL-coded carrot flakes powder (CFP) candidate reference material (RM) has been prepared from a lot of commercial carrot flakes. The candidate RM has been homogenized using a Robot Coupe blender fitted with titanium blades, carefully homogenized in large teflon/polypropylene containers, bottled in 1000 numbered polyethylene containers (20 g samples) and tested for homogeneity. Interlaboratory comparison studies for 9 essential elements, cadmium and total dietary fiber (TDF) based on the AOAC-method resulted in the characterization of the contents of those compounds in the above material. After exclusion of outliers, mean values from at least nine different laboratories based altogether on three independent analytical principles have been used to calculate the recommended concentration ranges for mineral elements. Testing of homogeneity and stability for β-carotene over a period of one year has been additionally carried out. The mean water content in the material amounted to 4.97% and remained stable over a one-year period. Homogeneity of the RM was within 3.0% for almost all included mineral elements as tested for a sample size of 0.5 g. The 95% confidence limits for the mean values of the established recommended concentrations of mineral elements in the present ARC/CL Carrot Powder candidate RM fell within 5% for all the other elements and TDF except for Fe (6.3%) and B (5.7%). The stability of β-carotene in the present candidate RM stored in darkness over a one-year period at room temperature was within 6.3%.     

The search for kinetic reference materials for adiabatic and differential scanning calorimetry

No reference materials are currently available to study thermoanalytical kinetic methods, apparatus, or software. The ASTM International Committee E27 on Hazard Potential of Chemicals seeks to identify possible calorimetric reference materials for evaluating kinetic parameters, including activation energy (E), log pre-exponential factor (log Z), and reaction orders (m and n), as well as reaction enthalpy (H). Six candidate materials are examined including di-tertiary-butyl peroxide (DTBP), trityl azide, azobenzene, azobisisobutyronitrile (ABIN), cumene hydroperoxide (CHP), and phenytetrazolthiol. No single material appears to meet all needs. The merits and applicability of each candidate are discussed and recommended kinetic reference values are presented.     

Development of clenbuterol reference materials: lyophilized bovine eye samples free of clenbuterol (CRM 673) and containing clenbuterol (CRM 674)

The certification by inter-laboratory testing of two candidate reference materials (RMs) for the mass concentration of the anabolic agent clenbuterol in bovine eye material is described: RM 674 with ca 10 microg clenbuterol per kg of eye matrix and RM 673 clenbuterol-free eye matrix as the negative control (<0.50 microg kg(-1)). Both candidate RMs were certified by eleven EU laboratories, and sixty-six accepted replicate measurements were included in the "Certification Study". The precision of the measurement process was assessed by calculation of the standard variation determined within each laboratory during the certification step. The study was performed according to the "Guidelines for the production and certification of BCR reference materials" and to "ISO guide 31, 33, and 35". The certified clenbuterol mass concentration for clenbuterol-free eye material CRM 673 (calculated on the basis of clenbuterol as the free base) was <0.50 microg kg(-1). The corresponding concentration for clenbuterol-containing eye material CRM 674 was 9.42 +/- 0.88 microg kg(-1). These certified values are very close to the desired target concentration of <0.5 microg kg(-1) and ca 10 microg kg(-1). This study has demonstrated that successful certification of clenbuterol-containing and clenbuterol-free bovine eye materials is possible.