Recent advances in the determination of low level plutonium in environmental and biological materials

The present paper reviews briefly the recent advance in radioanalysis of low level plutonium in environmental and biological samples. Lots of new radiochemical methods for determination of plutonium in aerosols, natural waters, soil, sediments and various biological materials have been developed. The use and prospects of several radiochemical procedures are discussed.     

Simultaneous determination of plutonium and americium in biological and environmental samples

A radiochemical method is given to determine the specific activity of²³⁸Pu, and²⁴¹Am from the global fallout in environmental and biological samples. The radiochemical recovery was for human livers Pu: 60–70%, Am: 40–60%; Bran: Pu: 50–70%, Am: 30–40%; Soil: Pu: 50–80%, Am: 30–50%. The resolution of the alpha-spectrum was for soils 30–40 keV and for livers and brans 40–60 KeV. To facilitate the wet ashing of large amounts of bran (15 kg), which are necessary to determine the presently very small activity concentrations of the transuranic elements in these types of samples, a fermentation process was employed. The procedure was tested by using NBS standard reference material and subsequently applied for the determination of Pu and Am from the global fallout in livers, plant tissues (bran), and soils.     

Pretreatment studies with biological and environmental materials

Summary A complete and down to the ultratrace level, i.e. down to a few ng/kg, nearly contamination free digestion for the subsequent mercury determination is possible in quartz vessels with HNO₃/HClO₄ mixtures (heating block, temperature up to 200°C). Very low mercury contents require especially purified acids. Vessels with volumes from 10 to 250 ml permit the digestion of samples up to 4g dry weight and 10g fresh weight. Duration of digestion depends on the matrix. For body fluids, tissue and plant materials typically approx. 1.5 h are required, for fatty materials 3 h and for sewage sludge approx. 8 h. A complete digestion of fatty materials is only possible in closed vessels with slight overpressure.

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Probenvorbehandlungsstudien mit biologischen und UmweltmaterialienIV. Vollständiger Naßaufschluß in teilweise und vollständig geschlossenen Quarzgefäßen zur nachfolgenden Spuren- und Ultraspurenbestimmung von Quecksilber

Zusammenfassung Ein vollständiger und bis in den Ultraspurenbereich, d.h. bis zu wenigen ng/kg, nahezu kontaminationsfreier Aufschluß zur Quecksilberbestimmung ist mit HNO₃/HClO₄-Gemischen in Quarzgefäßen (Heizblocktemperatur bis 200°C) möglich. Für sehr niedrige Gehalte müssen die verwendeten Säuren nachgereinigt werden. In Gefäßen von 10 bis 250 ml Inhalt können Probenmengen bis 4g Trocken- und 10 g Frischgewicht aufgeschlossen werden. Die Auf Schlußzeiten sind von der jeweiligen Probenmatrix abhängig und betragen für Körperflüssigkeiten, Gewebe- und Pflanzenmaterial etwa 1,5 h, für fetthaltiges Material etwa 3 h, für Klärschlamm etwa 8 h. Ein vollständiger Aufschluß fetthaltigen Materials ist nur im geschlossenen System mit leichtem Überdruck möglich.

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 70th birthday     

Pretreatment studies with biological and environmental materials

Summary In various biological and environmental materials the pressure pattern in closed teflon crucibles was followed after addition of nitric acid and heating. Hereby a significant influence of the matrix, of the temperature program and of the acid amount added on the pressure pattern was observed. The carbon balance, determined with the aid of gas-chromatography in several selected materials showed in no case a complete ashing and a very strong dependence of the decomposition rate on the kind of the investigated material.Part I: Fresenius Z. Anal. Chem. 291, 116 (1978); Part II: Fresenius Z. Anal. Chem. 293, 127 (1978)     

Pretreatment studies with biological and environmental materials

Summary Pressure digestion units made from stainless steel, with up to 12 sample positions, are described. The sizes of the teflon digestion crucibles are 0.6 resp. 35 ml for sample weights (dry weights) from about 10 up to 1000 mg. The handling of the units and the digestion crucibles, the standard digestion program with nitric acid (needed time including cooling period about 3 h), its evaluation and the very important safety aspects are extensively discussed.Supported by research grant MT 405 g/AUT 03 from the German Federal Department of Research and Technology (BMFT), Bonn, FRG     

The preparation of biological and environmental reference materials

The facilities of the Institute for Reference Materials and Measurements for the preparation of biological and environmental reference materials are discussed under the aspect of satisfying important parameters for the preparation of candidate reference materials. The choice of transformation methods and their possible influences on quality and long-term conservation, the need for automation as well as the importance of quality control are particularly emphasized.     

Preparation of biological and environmental reference materials at CBNM

Summary Since 1984, CBNM has been officially responsible for supporting the BCR programme for CRM storage, distribution and sale activities for the development of methods for preparation, conditioning and packing for reference materials, as well as actually preparing candidate CRMs. This has allowed CBNM to set up a new laboratory with unique facilities for the preparation of biological and environmental reference materials, in particular for organic and inorganic trace analysis. The main technical facilities developed at CBNM and additional equipment built to CBNM specifications by external companies are described. They have been used for the preparation of a variety of reference materials including cod fish, pig liver, offal, spiked milk, curd, orange juice, clover, lettuce, paprika, tomato, fly ash, soils and sediments.     

Elemental concentrations in nbs biological and environmental standard reference materials

Elemental concentrations reported by 325 investigators in 16 NBS SRM's are summarized. Mean values, standard deviations and comparative data from NBS and other reviews are provided.     

An anion exchange method for the determination of241Am and plutonium in environmental and biological samples

Irradiation and post-irradiation losses in 7 crude oils encapsulated in polyethylene and irradiated in a flux of 10¹²n·cm⁻² sec⁻¹ have been thoroughly studied. The fraction of mercury released during irradiations ranging from 10 minutes to 2 hours is proportional to the integrated flux received by the samples and does not differ substantially from one oil to another. Post-irradiation loss rates at 20°C range between 0.017 and 0.027%·hr⁻¹. Storage at−20°C reduces them by at least a factor of 2. The influence on the activity of¹⁹⁷Hg due to losses in sample weight occuring during the post-irradiation period has been examined. The fraction of radiomercury retained inside the walls of the irradiation vials versus the irradiation time has been assessed. Contamination of an inner irradiation site following prolonged irradiations of oils containing 150 μg/g of this element has been evaluated and found to have a negligible impact for trace measurements above the ng/g level.     

The determination of iodine in biological and environmental standard reference materials

Iodine is an element with excellent intrinsic sensitivity when determined by thermal neutron activation. However, in most real samples, the preponderance of chlorine and bromine, relative to iodine, makes the direct determination of iodine virtually impossible. Over the past 20 years, there probably have been as many publications on the separation of iodine as there have been for any other radionuclide. Upon review, however, the methods are essentially the same. After irradiation, the samples are subjected to a rapid destructive process to free the iodine from the matrix and then the iodine is separated from the other halides either by liquid-liquid extraction or by liquid ion exchange. Both of these procedures are, however, rather complex and do not effect a complete separation of the halides in one pass. In the work presented here, a simple procedure is described for the quantitative separation of iodine from chlorine. The procedure utilizes a gas phase separation on hydrated manganese dioxide with iodine collected on silvered quartz wool. The described procedure has been used for the determination of iodine in numerous new and old SRM's at the NBS.     

Elements very rapidly measurable by INAA in biological and environmental materials

In connection with the increasing usage of reference materials in INAA work, and with the continuing interest in this laboratory in rapid analyses via very short-lived induced activities, 13 biological and 8 environmental reference materials have been processed, under rapid analysis conditions, by the reactor-flux INAA Advance Prediction Computer Program. The results described show that a total of 33 induced (n, ) activities of 26 elements are detectable in these 21 reference materials, in total analysis times ranging from 1.5 to 192 seconds.     

Present status and future trends in biological and environmental reference materials in China

Summary The present status of biological and environmental reference materials (BERMs) is summarized, including the institutions involved in the preparation, certification and approval of BERMs, types, analysis, homogeneity, stability and role in analytical practice. The future perspectives on the BERMs in China are also briefly discussed.     

Overview about biological and environmental certified reference materials in the database COMAR

The Database COMAR now includes data from more than 8640 CRMs supplied by 180 producers in 24 countries. These data are divided into 8 main categories, containing up to 10 sub-categories. Quality of life as well as biological and clinical CRMs are two main categories where a great increase could be observed in the past years. These fields represent approximately 20|X% of the data records. Therefore it will be possible to gather different statistical information from these data.     

Determination of neptunium in plutonium materials by ICP-MS

An ICP-MS analytical method as an alternative to the current radiochemical method was developed to analyze trace level ²³⁷Np in bulk plutonium materials. In this method, ²³⁷Np is determined together with a suite of trace elements during a single analysis using one dissolution solution. Method validation was achieved through precision examination, spike recovery study, detection limit determination, comparison of results with the radiochemical method, and laboratory intercomparison studies on Pu metals. The ICP-MS method significantly reduced the analysis cost, the sample amount, consumption of chemicals and waste generation, as well as the sample turnaround time.     

Sources of misinterpretation for environmental plutonium measurements

Analytical and statistical uncertainties associated with low-level measurements may lead to spurious conclusions regarding the behavior of some plutonium isotopes. The general aspect of the methodology used in sample collection, preparation, radiochemical separation and alpha spectroscopy analysis of plutonium is considered. Biases and experimental artifacts that may produce inaccurate results and improper conclusions are discussed with examples from our research and from the open literature.