Characterization of a wheat flour reference material (ARC/CL) for twelve elements

Summary An ARC/CL coded wheat flour reference material (ARC/CL RM) with established recommended concentration values for 12 elements [1,2] was further characterized for P, K and Cr contents by means of an intercomparison study. Minor corrections were made to earlier recommended values in accordance with new results obtained. Fifteen laboratories using a total of 11 methods based on six entirely different analytical principles participated in the intercomparison study. The medians and standard deviations were calculated for the results of the intercomparison study. After rejecting as outliers values falling outside the median ± sd, the present recommended values were obtained by recalculating the median and 95% confidence limits. Recommended values were established for the major elements Ca, K, Mg, P, the minor elements Cu, Fe, Mn, Zn, and the trace elements Mo, Cr, Ni and Se. The relative standard deviations for the 95% confidence limits of the medians were lower than 10% for major and minor elements, 11% for Mo and 18% for Cr. All of the recommended concentration values fell into category A, having a high degree of confidence. The present RM, with its 16 recommended concentrations, is of value for use in nutritional, food composition and contaminant monitoring studies.     

Characterization of ARC/CL wheat flour, pork meat and skim milk powder reference materials for contents of toxic elements

Summary Wheat flour, pork meat and skim milk powder reference materials (RM) prepared and employed for the activities of the Sub-network on Trace Element Status in Food of the FAO European Cooperative Research Network on Trace Elements were subjected to an interlaboratory comparison study on the contents of Pb, Cd and Hg. The homogeneity of the above materials had earlier been shown to be within 2% for several essential elements and within 5 to 10% for Pb and Cd. An interlaboratory comparison study was conducted involving 17 reference laboratories recognized for their reliability and specialized in heavy metal determinations in biological materials. A total of seven methods based on four different analytical principles were employed to determine the contents of the above heavy metals. After the exclusion of outliers, the recommended concentration values expressed as the medians ±95% confidence limits were established. All of the recommended values reported here fell into category A, i.e. values recommended with a high degree of confidence according to the certification criteria established by Pszonicki. The present materials contain very low naturally occurring levels of all the heavy metals studied and have been successfully employed in the analytical quality control program of the above FAO study during the past five years.     

Characterization of ARC/CL wheat flour and potato powder reference materials for content of total dietary fiber

Summary ARC/CL wheat flour and potato powder reference materials (RMs) prepared by the Central Laboratory of the Agricultural Research Centre of Finland, earlier specified for contents of essential and toxic trace elements, were characterized for contents of total dietary fiber (TDF). Recommended concentration values established were obtained on the basis of an interlaboratory comparison study conducted involving 10 reference laboratories recognized for their reliability in TDF determinations. The recommended TDF contents established were based on an enzymatic-gravimetric method employed by the participating laboratories to determine TDF or water insoluble (WIS) and water soluble (WS) DF which were then added up to obtain TDF. After exclusion of outliers the recommended concentration values were expressed as the medians ±95% confidence limits of the average values by the participating laboratories. The coefficient of variation obtained for the recommended concentration range of TDF was within 7% for both RMs.     

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%.     

Characterization of a mixed diet reference material (NBS RM 8431) for inorganic elements and selected organic nutrients

Summary A mixed diet reference material was produced from a typical diet menu selected from a human study. It included foods for 3 meals consumed in a day. Recommended values for 17 elements and for ash, fat and protein are given. In addition information is provided for individual sugars, total sugar and starch, where recommended values cannot yet be given.     

Mixed total diet slurry as a prospective reference material

A total diet composite based on foods from the U.S. FDA Total Diet Study was investigated to assess its suitability as a slurry material as a candidate reference material in the form of a slurry. Results for the distribution of chlorine and sodium (overall variation 2% for Na and 3% for Cl) indicated no serious problems of sedimentation. Similarly determination of Co, Se, Rb, Sn, Fe and Zn covering an overall concentration (dry weight basis) range of 25 ng/g for Co to 33 g/g for Fe and Zn, suggests that the homogeneity of the composite is reasonably good. However the operational steps adopted for this preliminary investigation were not optimal. Use of a high pressure diffusion type of approach adopted by the National Research Council of Canada in preparing the lobster hepatopancreas matrix (LUTS-1) should further improve the homogeneity characteristics of the slurry.     

Characterization of a potato reference material for major, minor and trace elements

Summary A potato reference material (RM) was prepared for the analytical quality control program to be employed by the Sub-network on Trace Elements in Food of the FAO European Co-operative Network on Trace Elements. Approximately 50 kg of commercially available potato granules prepared from baked, mashed and roller-dried potatoes, containing 2.8% ash and 3 mg/kg added butylhydroxyanisole was purchased. The granules were carefully homogenised in large glass cylinders followed by division into 50 g portions into numbered acid-washed bottles. The bottled material was tested for homogeneity by taking ten bottles throughout the bottling line and determining by validated atomic absorption spectrometric methods 1.0 g samples for seven mineral elements. Homogeneity for Mg, Ca, Zn, Fe, Mo, Ni and Cd was better than 5%. An international network on experienced, high-quality reference laboratories was established to conduct an interlaboratory comparison study on the determination of 14 mineral elements in the RM. A total of seven methods based on independent analytical principles were employed by the reference laboratories. After excluding outlying analytical results, the criteria defined by the IAEA were used for classification of the overall medians obtained through the interlaboratory comparison study. The relative standard deviations for the 95% confidence limits of the medians were as follows: P=4.2%, K=0.7%, Na=4.7%, Ca=5.5%, Mg=2.4%, Fe=9.3%, Mn=4.0%, Zn=3.6%, Cu=4.7%, Mo=23%, Ni=22%, Cr=19%, Pb=11% and Cd=4.6%. With the exception of Cr, all of the recommended concentration values obtained for the above indicated elements fell into category A, i.e. values recommended with a high degree of confidence according to the classification criteria of the IAEA. The present RM is the only certified potato RM currently available for mineral elements.

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Charakterisierung eines Kartoffel-Referenzmaterials für Haupt-, Neben- und Spurenelemente

     

Characterization (certification) of three wheat flours and a wheat gluten reference material (NIST RM 8436, 8437, 8438 and 8418) for essential and toxic major, minor and trace element constituents

Summary Three wheat flours, Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437), Soft Winter Wheat Flour (NIST RM 8438) and Wheat Gluten (NIST RM 8418) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition by analysts in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods yielded 16–27 best estimate and 3–8 informational concentration values for each of these materials. These reference materials are intended for analytical quality control of element determinations in flour and flour products as well as other agricultural/food materials with related matrices.Contribution No. 92–145 from Centre for Land and Biological Resources Research     

Human albumin as a reference material for trace elements

Summary An investigation through interlaboratory comparison using different analytical techniques has been carried out in order to assess the suitability of a plasma protein solution as a source for a trace element reference material in clinical analysis. Reasonable agreement was obtained for a number of elements from the range studied: Al, Ba, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Sr, V and Zn. The techniques used included flame and furnace atomic absorption spectrometry (FAAS and ETA-AAS), furnace atomic emission spectrometry (ETA-AES), inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and simultaneous multi-element atomic absorption spectrometry (SIMAAC). Results indicated that this plasma protein solution may prove useful as a source for a reference material covering trace element levels outwith the range found in normal human plasma.

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Humanalbumin als Referenzmaterial für Spurenelemente

     

Instrumental neutron activation analysis for essential and toxic elements in Kenitra city (Morocco) foods

The aim of this study is to evaluate the sensitivity of Ko-method of Instrumental Neutron Activation Analysis for minor, trace and toxic elements in the most consumed foodstuff purchased from large commercial markets in Kenitra’s city (Morocco) which has been chosen for a pilot project on food monitoring in the west of Morocco. Samples have been analyzed by Ko-INAA method using TRIGA Mark II reactor at Josef Stefan Institute in Slovenia. The quality control of results was assessed using the Standard Reference Material SRM 1547 (Peach leaves). Results show an adequate sensitivity for the most studied elements in foodstuffs except for beef, onion and whole wheat which show a high sensitivity factor for Cd and As. INAA seems to be an adequate choice for element analysis in foodstuffs.     

Biological reference materials and analysis of toxic elements

Summary Biological monitoring of toxic metal pollution in the environment requires quality control analysis with use of standard reference materials. A variety of biological tissues are increasingly used for analysis of element bioaccumulation, but the available Certified Reference Materials (CRMs) are insufficient. An attempt is made to review the studies made using biological reference materials for animal and human tissues. The need to have inter-laboratory studies and CRM in the field of biological monitoring of toxic metals is also discussed.

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Biologische Referenzmaterialien und Analyse toxischer Elemente

     

Honey as a candidate reference material for trace elements.

The feasibility of producing and certifying new certified reference materials (CRMs) for trace elements in honey was investigated. Preliminary steps for preparation of candidate materials are performed at the Institute for Reference Materials and Measurements, Joint Research Centre of the European Commission (EC-JRC-IRMM). Two different types of honey, Acacia and Eucalyptus, were tested for determination of 10 trace elements. To each type of honey was added a given amount of high purity deionized water to obtain aqueous solutions with an acceptable degree of homogeneity which would require only minimal manipulation before analysis. Average values obtained for the trace elements by means of inductively coupled plasma-based techniques were as follows (in microg/ kg +/- SD): Acacia honey, As, 1.10+/-0.20; Cd, 0.328+/-0.035; Cr, 1.90+/-0.22; Cu, 67.0+/-5; Fe, 215+/-30; Hg, < 0.75; Mn, 82.1+/-6.2; Ni, 21.0 3.0; Pb, 2.30+/-0.25; Se, 9.10+/-1.2; Zn, 167+/-22; Eucalyptus honey, As, 5.99+/-0.10; Cd, 0.592+/-0.074; Cr, 1.50+/-0.07; Cu, 219 24; Fe, 1008+/-114; Hg, <0.75; Mn, 1009+/-51; Ni, 11.3+/-1.5; Pb, 5.00+/-0.40; Se, 5.60+/-0.91; Zn, 791+/-91. When these 2 pilot materials are ready, the certification project will be launched in full compliance with current rules set by EC-JRC-IRMM. If the project is successful, the new CRMs will be put primarily at the disposal of the National Reference Laboratories for trace elements.     

Certified reference material for quantification of polycyclic aromatic hydrocarbons and toxic elements in tunnel dust (NMIJ CRM 7308-a) from the National Metrology Institute of Japan

The National Metrology Institute of Japan has issued a certified reference material of tunnel dust for polycyclic aromatic hydrocarbons (PAHs) and toxic element analyses. PAH certification was performed using isotope dilution mass spectrometry with deuterium-labeled PAHs as internal standards. Three extraction techniques (microwave-assisted extraction with toluene/methanol, Soxhlet extraction with toluene, and pressurized liquid extraction with toluene) were used, and the extracts were measured by gas chromatography/mass spectrometry with two different columns. For values of PAHs, 11 PAHs are provided as certified values between 0.294 and 20.3 mg/kg, and five PAHs are provided as information values. Certified values of five toxic elements (Cr, Ni, Pb, Mn, and Cd) obtained from microwave-assisted digestions and a combination of measurement techniques are also provided between 43.4 and 10.71 × 10³ mg/kg.     

Determination of essential and toxic elements in Libyan foodstuff using instrumental neutron activation analysis (INAA)

Since there is no database in Libya defining the intake of the individuals from different essential (minor and trace) and toxic elements provided through food, drinking water and aerosol, a project has been proposed with the cooperation of IAEA to determine the concentration of a number of elements such as Cs, Fe, Cr, Rb, Sc, Se, Co, Zn in the three mentioned sources. Emphasis was placed on the use of nuclear and nuclear-related techniques. In this paper, the primary results are presented for the concentration of minor and trace elements in some vegetables, spices and other foods which are widely used in the Libyan meals. Instrumental neutron activation analysis utilizing a 10 MW water pool reactor and a γ-ray spectroscopy facility was employed. For quality control, certified reference materials were analyzed simultaneosly with the samples which show good agreements compared with the certified data. Emphasis was given to both elements iron and zinc for their importance.     

Simulation of Iranian total mixed diets and their analysis for essential and toxic trace elements using nuclear and complementary analytical techniques

Neutron activation analysis, inductively coupled plasma emission spectrometry(ICP-ES) and atomic absorption spectroscopy (AAS) have been used to determineactual daily dietary intakes of minerals and trace elements in the Iranianpopulation. This article deals with the trace elemental analysis of dailydiets of the Iranian population differentiated with respect to food habits,geographical variability, literacy and income. Three study groups in fiveregions were defined. Thirty total daily diet samples were prepared basedon the method of dietary records. Also a few samples representing the intakesof two other study groups, males and females, were prepared by the duplicatediet method. Therefore, this study not only covered representative dietarypatterns of almost all adult people in Iran in a pilot study, but it alsopermitted to check the validity of the sampling methodology for total mixeddiet simulation.     

Dietary intakes of essential trace elements: Results from total diet studies supported by the IAEA

Summary The International Atomic Energy Agency (IAEA) has, for many years, supported research on human dietary intakes of trace elements taking advantage, for analysis, of the possibilities offered by nuclear techniques, particularly neutron activation analysis (NAA). This paper summarizes the results obtained from studies in more than 20 countries in which special emphasis was placed on the application of reliable methodologies (written protocols, special equipment, analytical quality control, etc.). Considerable variation was observed among dietary intakes of essential minor and trace elements though most elements showed a pattern of adequate nutrition in most countries. However, for some elements such as calcium, iodine, iron and zinc, the intakes in many countries were lower than the dietary requirements.     

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 new Antarctic certified reference material for trace elements: Adamussium colbecki

The certification of a new reference material for trace elements based on the Antarctic bivalve Adamussium colbecki is reported. This certified reference material (CRM), labelled IRMM 813, was produced in the frame of the Italian National Program for Research in Antarctica (Programma Nazionale di Ricerca in Antartide, PNRA). About 40 kg of the scallop were collected at Terra Nova Bay (Ross Sea). The raw material was freeze-dried, jet-milled and homogenized so as to make it suitable for certification. The elements selected for the certification project were As, Cd, Cu, Cr, Fe, Mn, Ni and Zn. Homogeneity and short- and long-term stability were preliminarily investigated so as to assess the suitability of the freeze-dried mass as a candidate CRM. The candidate material was found to be fit for purpose, thus allowing the following phases of the certification project to be undertaken, in the first place the selection of expert laboratories for the accomplishment of the certification campaign. Eighteen laboratories from twelve countries accepted to participate in the certification project which thus could be successfully completed.