Application of neutron activation analysis for trace element determinations in biological materials

Over the past three decades, more and more interest has been focused on trace eleemnts in biological materials. This increasing interest has gone hand in hand with the continuous improvement of analytical techniques. Neutron activation analysis has proven to be a most suitable method for the quantitative determination of a wide variety of trace (0.01–100 μg g^?1) and ultratrace (<0.01 μg g^?1) elements in biological materials. This technique has even played a preponderant role in this field.     

Survey and evaluation of available biological reference materials for trace element analysis

Summary A database recently prepared by IAEA contains information on 60 internationally available biological reference materials (BRMs) from 9 producers. The data recorded for each material include: name, code No., cost, list of elements, and minimum weight of material recommended for analysis. For each element the concentration and its confidence interval (CI) are recorded, as well as an indication of whether the concentration value is certified or noncertified (e.g. an information value).Large differences among producers are observed in respect of how the concentration values and their CIs are defined, and how other relevant information is reported in the certificates of analysis. International recommendations on how this should be done generally do not seem to be followed.For several elements of biomedical interest there is a serious lack of BRMs namely: Al, F, I, Mo, Si, Sn and V. In addition, the CIs for the following elements are generally excessively large: Al, As, Cd, Cr, Hg, Mo, Ni, Se and V.     

Applications of mass spectrometry in the trace element analysis of biological materials

The importance of mass spectrometry for the analysis of biological material is illustrated by reviewing the different mass spectrometric methods applied and describing some typical applications published recently. Though atomic absorption spectrometry is used in the majority of analyses of biological material, most mass spectrometric methods have been used to some extent for trace element determination in biomedical research. The relative importance of the different methods is estimated by reviewing recent research papers. It is striking that especially inductively coupled plasma mass spectrometry is increasingly being applied, partly because the method can be used on-line after chromatographic separation, in speciation studies. Mass spectrometric methods prove to offer unique possibilities in stable isotope tracer studies and for this purpose also experimentally demanding methods such as thermal ionization mass spectrometry and accelerator mass spectrometry are frequently used.     

Certified reference materials of soils and sewage sludges for the quality control of trace element environmental monitoring

For the wide variety of soil/sludge matrices encountered in analytical practice, a range of CRMs should be available to verify the analytical quality control of any determination carried out, using samples which should be as similar as possible to real soil and sludge samples so that the method's performance may be tested under real analytical conditions. This paper presents basic requirements for the preparation of soil and sludge CRMs for the quality control of trace element determinations (total and extractable contents, following strict extraction protocols), and gives recent examples of new certifications successfully concluded by the SM&T programme of the European Commission.     

A comparison of neutron activation analysis and inductively coupled plasma mass spectrometry for trace element analysis of biological materials

Fifty individual food types were analysed by instrumental and radiochemical neutron activation analysis as well as inductively coupled plasma mass spectrometry after testing all techniques by analysing IAEA mixed human diet, H-9. The performance of these trace element techniques and their limitations were evaluated under normal, routine, multi-element surveys of a large range of solid biological materials.South Australian Department of Agriculture, 21 Divett Place, Adelaide, SA, Australia.     

Quality control with CRMs for trace element determination in candidate reference materials

Summary Three soil samples and five candidate materials of biological origin (bovine muscle, bovine kidney, bovine blood, rye flour and wheat flour) and one already certified RM (Bovine Liver, 12-02-01) were analyzed for their contents of Cd, Cu, Cr, Pb and Zn. Pressure digestion with nitric acid in PTFE (at 180°C) and quartz (at 290°C) vessels was used for sample decomposition. The measurements were made by graphite furnance atomic absorption spectrometry (ET-AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and square wave voltammetry. The accuracy of analysis has been checked by simultaneous analyses of six similar CRMs. An excellent agreement between the found and certified values is illustrated by highly significant correlations.     

Microwave assisted extraction for trace element analysis of plant materials by ICP-AES

Application of microwave assisted extraction for the decomposition and dissolution of plant samples for trace metal determination by ICP-AES was examined. Dried onion, leaves of spinach beet and three reference materials CTA-OTL-1, CTA-VTL-2 and CL-1 were analyzed. Water, EDTA and hydrochloric acid (0.01, 0.10 and 1.0 M, respectively) were used as leaching solutions. The extraction efficiency was investigated by comparison of the results with those obtained after microwave wet digestion. HCl was found to be very suitable for quantitative extraction of B, Ba, Cd, Cu, Mn, Ni, Pb, Sr and Zn from the samples. For reference materials, the measured concentrations are well consistent with the certified values. The use of EDTA led to a complete extraction of B, Cd, Ni, Pb, Sr and Zn. Water was found to be a good leaching solution for boron. For extraction with HCl and EDTA, the RSD values for the concentrations measured were below 8% for most of the elements.     

Target preparation of biological samples for trace element analysis using nuclear techniques

An easy and rapid method for preparing biological targets for trace element analysis using nuclear techniques involving charged particle beams is described. The targets are thin, homogeneous and uniform. They withstand 100 nA of 1–2 MeV proton beams and of 5–10 MeV alpha beams for about 10 hrs.     

Microwave assisted extraction for trace element analysis of plant materials by ICP-AES

Application of microwave assisted extraction for the decomposition and dissolution of plant samples for trace metal determination by ICP-AES was examined. Dried onion, leaves of spinach beet and three reference materials CTA-OTL-1, CTA-VTL-2 and CL-1 were analyzed. Water, EDTA and hydrochloric acid (0.01, 0.10 and 1.0 M, respectively) were used as leaching solutions. The extraction efficiency was investigated by comparison of the results with those obtained after microwave wet digestion. HCl was found to be very suitable for quantitative extraction of B, Ba, Cd, Cu, Mn, Ni, Pb, Sr and Zn from the samples. For reference materials, the measured concentrations are well consistent with the certified values. The use of EDTA led to a complete extraction of B, Cd, Ni, Pb, Sr and Zn. Water was found to be a good leaching solution for boron. For extraction with HCl and EDTA, the RSD values for the concentrations measured were below 8% for most of the elements. Received: 4 May 2000 / Revised: 20 June 2000 / Accepted: 22 June 2000     

Certified reference material (CRM 414) for the quality control of trace element analysis in plankton

Summary Analyses of plankton are performed by a number of organisations to investigate the transfer and uptake of toxic elements along the trophic chain and to monitor the levels of contamination of different aquatic environments. In order to obtain reliable transfer functions in environmental models or to use plankton as an indicator organism for the assessment of environmental pollution, these analyses should give accurate results. As accuracy requires quality control and the application of certified reference materials (CRMs), a certification campaign has been conducted by the Community Bureau of Reference (BCR). A plankton material was collected in a freshwater pond, lyophilised, homogenised and bottled and its homogeneity and long-term stability were verified. The material (CRM 414) was analysed by a group of 15 selected laboratories having given proof of their adequate QC and using different analytical methods. The contents of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn are certified. This paper presents the certification work performed.     

Czechoslovakian biological certified reference materials and their use in the analytical quality assurance system in a trace element laboratory

Summary The Trace Element Laboratory of the University of Agriculture in Prague (CSFR) participated successfully in interlaboratory experiments on the determination of the contents of trace elements in seven Czechoslovakian reference materials. Czechoslovakian certified reference material CRM 12-02-01 (Bovine liver) was used for the development of a new analytical method using the Dry Mineralizer Apion as well as in analytical quality assessment of data in the determination of Cd, Pb, and Hg contents in routinely analyzed animal tissues.     

Certified reference material (CRM 397) for the quality control of trace element analysis of human hair

Summary Analyses of human hair are routinely performed by a number of organisations to monitor the level of exposure of a population to toxic elements, e.g. heavy metals. To control the quality of such determinations, the Community Bureau of Reference (BCR) has produced a reference material (CRM 397) certified for its contents of Cd, Hg, Pb, Se and Zn. This material was collected in a moderately contaminated area, carefully prepared and its homogeneity and long term stability were verified. This paper presents the certification work performed.     

Database for trace element concentrations in biological samples

Summary Numerous methods have been published for the determination of the concentration of elements such as arsenic, cadmium, chromium, mercury and nickel in biological samples as blood, tissues and urine. It is not easy but highly desirable to assess the reliability of such methods. Several publications present values of trace element levels in samples from apparently healthy subjects as well as from persons with different diseases and after various exposures. Very often published normal values for unexposed subjects differ much — even up to one order of magnitude. There are major problems related to sampling, definition of the reference groups and analysis. Values for such groups can be called reference values rather than normal values.Therefore it is difficult even for experts to find such accurate and typical values to be used for comparative purposes e.g. in toxicology and occupational medicine. Knowledge is desirable of an average value and also of the respective frequency distribution. In this paper factors are discussed influencing the values such as selection of the reference groups and how to get typical reference intervals. We have worked for several years with developing methods for trace element determination and with evaluating data for use in e.g. occupational health. Therefore we felt a need for systematic evaluation accessible through a database.The original publications are retrieved by careful literature data search in e.g. Medline and Chemical Abstracts. We plan to offer discettes with evaluated typical concentrations of elements, specified details of sampling and analysis, reliability as well as references to the original publications. These discettes are very easy to use. A frequently updated and easily accessible database system should be very useful. Cooperation is planned with e.g. International Commission on Occupational Health, International Atomic Energy Agency (IAEA), International Labour Organization (ILO), International Union of Pure and Applied Chemistry (IUPAC), National Institute of Occupational Safety and Health (NIOSH in USA) and the World Health Organization (WHO).

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Datenbasis für Spurenelementkonzentrationen in biologischen Proben

     

New marine biological reference materials for trace metals

Summary A list of reference materials and certified reference materials (CRM's) useful to the marine analytical chemist for validation of trace element determinations is given. The preparation and certification for the trace element content of two new marine biological reference materials, dogfish flesh (DORM-1) and dogfish liver (DOLT-1), is described.     

Determination of trace fluorine in biological materials by photonuclear activation analysis

Summary By using the photonuclear activation technique, fluorine has been determined in biological materials. After alkali fusion, fluorine is adsorbed on an anion exchange resin. The irradiated resin sample is soaked and stirred in 5N hydrochloric acid solution. After filtering, fluorine-18 resulting from the (, n) reaction was extracted with 0.2 % dimethyldichlorosilane in xylene. The fluorine-18 0.51 MeV annihilation peak in an aliquot of the organic phase was measured by gamma-ray spectrometry. The precision of this method calculated from replicate analyses of standard specimen is ±11 % and sensitivity is estimated as 0.01g for this element.

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Zusammenfassung Mit Hilfe der photonuklearen Aktivierung wurde Fluor in biologischem Material bestimmt. Nach der Alkalischmelze wird das Fluor an einem Anionenaustauscher adsorbiert. Das bestrahlte Harz wird in5-n Salzsäure eingerührt und zum Quellen gebracht. Nach dem Abfiltrieren wird das aus der, n-Reaktion stammende¹⁸F mit einer 0,2% igen Lösung von Dimethyl-dichlorsilan in Xylol extrahiert. In einem aliquoten Anteil der organischen Phase wird es gammaspektrometrisch gemessen. Die Genauigkeit des Verfahrens wurde durch wiederholte Analysen von Standardproben ermittelt und beträgt ±11%. Die Empfindlichkeit wurde zu 0,01g geschätzt.

     

Collection and preparation of a second generation biological reference material for trace element analysis

The paper describes the collection and preparation of a second generation biological reference material (human blood serum) with trace element levels closely approximating those in real human blood plasma or serum samples.     

Radiochemical separations for inorganic trace elements in some biological reference materials,foods, tissues and body-fluids

A simple radiochemical machine incorporating ion-exchange procedures has been described. The system has been tested repeatedly for the determination of Cd, Co, Cr, Cu, Mn and Mo at ultra trace concentration levels in a variety of biological samples such as reference materials, human blood serum, human milk, hair and certain dietary materials, thereby demonstrating its suitability for practical use. The procedure can also yield results for A, Au and W, without any further chemical manipulations. Results show <1, 0.12, 0.18, 983, 0.61 and 0.91 g/l for Cd, Co, Cr, Cu, Mn and Mo, respectively, in human blood serum. Corresponding concentrations in human milk are <1, 0.25, <1, 186 to 310, 4 to 40 and 5.8 g/l. Among the reference materials, IAEA milk standard A-11 shows 1.85, 5.1, 17, 380, 260 and 101 ng/g for Cd, Co, Cr, Cu, Mn and Mo, respectively. Corresponding concentrations in animal muscle H-4 are 4.1, 5, 10.2, 4000, 455 and 45 ng/g. Importantly, this scheme has been applied to process large number of samples from single investigations such as those arising from dietary studies, obtaining quick and reliable data for routine use.In memory of Knut Samsahl, the devoted Norwegian radiochemist.