Determination of lead in biological and environmental samples by203Pb isotope dilution substoichiometric method

A procedure for the determination of lead in various biological and environmental samples by²⁰³Pb radioisotope dilution substoichiometric method is presented. The accuracy of the method by comparison with the literature values of reference materials appears to be good. The standard deviation of the method is less than 10%, and detection limit is about 0.1 g of lead.     

Radiochemical neutron activation analysis of chromium in biological materials using ion chromatography with “on-line” yield determination

The use of ion chromatography with continuous UV detection for radiochemical separation of Cr with simultaneous yield determination is presented. The RNAA method consists of sample destruction in HNO₃+HClO₄, extraction of Cr(VI) with tribenzylamine in CHCl₃, backextraction in NaOH and chromatography of chromate. From radiotracer experiments, the ratio of signals for⁵¹Cr and Cr spike was found to be constant for a chromium mass range of 15 to 100 g. Application of the RNAA method to Cr determination in biological reference materials showed a reasonable agreement with the reference values. A relative standard deviation of 3% on the 100 g/kg level for homogeneous material was achieved.IAEA-fellow, on leave from the Philippine Nuclear Research Institute Philippine     

Methyl mercury determination in environmental and biological reference and other materials by quality control with certified reference materials (CRMs)

Summary Two concentration methods — HCl extraction and extraction followed by water vapour distillation — prior to anion exchange separation and cold-vapour atomic absorption spectrometry were used for the quantification of methyl mercury in a number of reference materials of biological and environmental origin with reference or certified total mercury contents. The applied methods were validated by the analysis of three marine reference materials, certified for methyl mercury. The results obtained in the materials with methyl mercury contents ranging from less than 1 g/kg to a few hundred g/kg showed good agreement between both methods for biological materials, whereas extraction/anion exchange resulted in somewhat too high values for a number of environmental materials. These findings, however, require further confirmation by additional methods and by other laboratories.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Utilization of a boron irradiation vessel for NAA of short-lived radionuclides in biological and geological materials

A boron nitride irradiation vessel designed for use with a pneumatic tube transfer system has been used to analyze short-lived radionuclides by NAA. Bare and Cd-shielded irradiations on Co, Zr and Au were made to characterize the neutron fluxes in the irradiation position. Bare and BN-shielded irradiations were performed to determine epithermal advantage factors for 16 short-lived reactions and interference factors for a total of 11 (n, p) and (n, ) reactions induced by reactor fast neutrons. To illustrate application of these data, several biological and geological reference materials were analyzed.     

Thallium determination in biological materials by radiochemical neutron activation analysis

Summary The determination of thallium in biological materials sometimes cause problems because of the low concentrations of this toxic element. In the present work a method is described which optimizes the parameters affecting the specificity and sensitivity of the radiochemical NAA of thallium in biological samples. High thermal neutron flux, complete decomposition of the organic matter by pressurized digestion, TlI precipitations, liquid extraction of HTlBr₄ and La(OH)₃ scavenging purification are the steps leading to the final homogeneous preparation of Tl₂CrO₄ for -activity measurement. The method was applied to various materials as bovine liver, bone and nails. Good agreement was found between certified and determined thallium concentrations of the reference material CRM 176. The chemical yield comes to about 80%, with low deviations. The sensitivity of the method is about 10^–3 g/g, the standard deviations being in the range of 3.6% (CRM 176), 14% (bovine liver), and 17% (bone). Detailed working instructions are given.     

Preliminary homogeneity study of in-house reference material using neutron activation analysis and X-ray fluorescence

Summary Although many biological reference materials for quality control of trace element analysis are commercially available, there is still a need for additional local materials for special matrices. In the Latin American region a preliminary study has been commenced involving analytical strategies for the characterization of in-house reference material. A biological sample, prepared in Brazil, constitutes the first regional attempt to prepare reference material. It was analyzed by neutron activation analysis (NAA) and X-ray fluorescence (XRF) to verify its homogeneity. The determination of the trace elements and certain major elements was carried out by instrumental NAA. Trace elements such as Cd, Mn, Mo and Cu were determined using NAA with radiochemical separations to improve the sensitivity and precision. XRF was applied only to major constituents and some trace elements with concentration of more than 10 g/g. From a total of 18 elements analyzed, only Fe, Cr and Sc were not homogeneously distributed.     

Dithiocarbamate extraction of trace amounts of selenium from biological samples for neutron activation analysis

A three-step method has been developed for extracting trace amounts of selenium from biological samples for neutron activation analysis /NAA/. After acid digestion, the sample is first extracted with lead diethyldithiocarbamate at pH 4 to remove a number of interfering elements. Next, selenium is extracted with sodium diethyldithiocarbamate into chloroform at pH 1.5. Finally, selenium is back-extracted with concentrated nitric acid for NAA. Analysis of selenium extracted from four standard reference materials resulted in excellent agreement with the certified values of selenium concentration. A detection limit of 0.05 g has been achieved.     

Determination of Cd,Mo, Cr and Co in biological materials by RNAA

A method for the determination of trace amounts of Mo, Cd, Co and Cr in biological materials by neutron activation analysis with radiochemical separation is presented. The method is based on the ion-exchange scheme developed by SAMSAHL, where Co and Cr are trapped on BioRad Chelex-100 and Cd and Mo on BioRad AG2X8. The elements Mo, Cd and Co can be determined without systematic errors. For the element chromium the situation is less clear, partially due to lack of sufficient certified reference materials for Cr. The method has been used in the characterization of candidate reference materials. Detection limits in these materials range from 1.5 g/kg for Co to 10 g/kg for Cr. Actual levels as low as 8 g/kg for Cd and 7 g/kg for Co were measured.     

Application of standard materials and standard reference materials in the analysis of lead in blood

Summary Valuable information can be obtained at little expenses from quality control samples prepared in-house to monitor the determination of blood lead by atomic absorption spectrophotometry. Commercially manufactured control materials can also be used for this purpose. These materials are compared to standard reference materials which at present are available.The relative standard deviations for analysis of NBS standard reference materials were 15.4–2.8% (range 60–754 g/l) and in agreement with the relative standard deviation estimated for the analytical method. The corresponding figures for BCR control reference materials were lower: 1.1–1.4% (range 134–795 g/l).The average analytical bias demonstrated by analysis of NBS standard reference material and BCR control reference material were 3–6% (range 795–60 g/l) and in agreement with bias estimated by analysis of commercially manufactured and in-house prepared control materials.     

Radiochemical scheme for the determination of molybdenum and uranium in biological materials by NAA

A new universal radiochemical separation scheme for selective and quantitative isolation of molybdenum and neptunium (formed from uranium), from neutron irradiated biological materials has been elaborated. The procedure is based on ion exchange and extraction chromatography with final fixation of molybdenum on a column with -benzoinoxime supported on Bio-Beads SM2 and neptunium on Dowex 1-X8 [No ₃ ^– ]. The separated elements are quantified using gamma-spectrometric measurements. The new NAA method is able to overcome problems associated with high contents of phosphorous in some samples and assures detection limits better than 3 ppb for both elements. The validity of the proposed scheme has been demonstrated by the analysis of several CRM's.     

Analytical quality control by solid sampling GFAAS in the production of animal tissue reference materials: lead and cadmium in bovine liver reference materials

Summary The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of bovine liver reference material is described. Analytical quality assurance was achieved by using a wet digestion decomposition procedure and GFAAS (WD-GFAAS) as well as three different methods of SS-GFAAS. It will be shown, that SS-GFAAS is an adequate and efficacious method of analytical quality control in the production of reference materials. Details are given about the preliminary steps of sample selection and preparation, applying SS-GFAAS both as a screening method and for the detection of contamination during the production of the reference materials. The element contents of the four bovine liver materials measured after decomposition with nitric acid in the open system by GFAAS and also by Flame-AAS, using the slotted tube atom trap, are compared statistically with the results obtained by SS-GFAAS. In solid sampling analyses three different systems were applied: a solid sampling ZAA-spectrometer with platform-boat, a D₂AA-spectrometer with solid sampling graphite tube and platform-drawer and an autoprobe-D₂AA-spectrometer with solid sampling autoprobe and graphite tube.     

Indirect atomic absorption spectrometric determination of silicon in gallium arsenide using an amplification reaction

Summary An indirect method is described for determining silicon in Si-doped gallium arsenide by electrothermal atomic absorption spectrometry using an amplification reaction. After sample decomposition, arsenic is removed by evaporation in the presence of hydrochloric acid, hydroxylammonium chloride and potassium bromide. Silicon is extracted into MIBK as silicomolybdic acid. The organic phase is injected into the graphite furnace and the molybdenum content is finally determined. The detection limit (6s) is 0.7 g Si/g GaAs. The method has been applied to the analysis of some Si-doped samples. The RSD of the overall procedure is 5.9–14.8% in the range 1.4–2.7 g/g.     

Determination of uranium and thorium concentrations in integrated circuit packaging materials

The purpose of the present research is to find a suitable technique to measure trace amount of uranium and thorium and to determine the surface -flux in silicon compound /SiO/ used for fabrication of integrated circuit packaging materials. Among several commonly-used detecting techniques, it was found that neutron activation analysis /NAA/ was most promising. The results from NAA show a large difference in uranium and thorium concentrations when cadmium and boron carbide shields are used, whereas -flux measurements show a low -activity, which corresponds to the trace amount of uranium and thorium expected to be present in these materials.     

Adsorption voltammetric techniques for the determination of uranium(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone as complex forming reagent

Uranium (VI) can be determined by adsorptive voltammetric techniques, as its chloranilic acid complex, over a wide concentration range. Differential pulse polarography is useful for quantification of uranium between 0.1 and 1.5 mg/l; for the range from 10 to 500 g/l differential pulse voltammetry and for ultra-trace analysis between 0.024 and 40 g/l adsorptive stripping voltammetry are preferred. The standard deviation for the 3-detection limit of 24 ng/l uranium was found to be 8%. In the trace analysis of metals in aquatic environmental systems by adsorptive stripping voltammetry it is normally necessary to decompose polluted water samples by UV irradiation or microwave digestion. The advantage of the developed method is the fact that no sample pretreatment is necessary.Dedicated to Professor R. Geyer on the occasion of his 80th birthday     

Massenspektrometrische Iodspurenbestimmung in geochemischen Standard-Referenzmaterialien und in Meteoriten

Zusammenfassung Die massenspektrometrische Isotopenverdünnungsanalyse wird erstmalig zur Iodspurenbestimmung in Gesteinsproben, wie z. B. in geochemischen Standard-Referenzmaterialien und Meteoritenproben, eingesetzt. Für den Iodnachweis im Massenspektrometer werden negative I^–-Thermionen in einer Rhenium-Zweiband-Ionenquelle unter Verwendung eines Lanthansalzes als Ionisierungshilfe erzeugt. Als Indicatorisotop zur Isotopenverdünnung wird das langlebig-radioaktive ¹²⁹I verwendet. Der Aufschluß der Proben geschieht mit Flußsäure in einer Teflonbombe, wobei anschließend das Iod als AgI isoliert wird. Während ohne Zugabe einer Sulfitlösung nur ein geringer Anteil des Iods isoliert werden kann, erhöht sich die Isolierungsausbeute auf über 75% bei Vorhandensein dieses Reduktionsmittels. Mit dieser Methode werden einige geochemische Standards des Centre de Recherches Pétrographiques et Géochimiques in Nancy sowie verschiedene antarktische und nichtantarktische Steinmeteorite analysiert. Die dabei bestimmten Gehalte schwanken vom unteren ng/g- bis in den g/g-Bereich, wobei relative Standardabweichungen von 2–3% bei Gehalten > 100 ng/g erhalten werden. Die Nachweisgrenze liegt bei etwa 6 ng/g. Das beschriebene, massenspektrometrische Verfahren eröffnet als definitive Methode die Möglichkeit, erstmals auch Iodspuren in geochemischen Standards zertifizieren zu können. Bei der Anwendung auf antarktische Meteorite konnte damit auch ein Iodüberschuß in einigen dieser Proben gegenüber dem normalerweise bekannten Iodgehalt nicht-antarktischer Meteorite bestätigt werden. Für Iodgehalte ab dem oberen ng/g-Bereich wurde auch eine iodid-selektive Elektrode in Verbindung mit einem alkalischen Aufschluß und einer chromatographischen Abtrennung erfolgreich eingesetzt. Bei Verwendung von Sulfit als Reduktionsmittel lagen hier die Isolierungsausbeuten bei etwa 85%.

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Mass spectrometric iodine trace determinations in geochemical standard reference materials and in meteorites

Summary Isotope dilution mass spectrometry is being used for the first time to analyse iodine traces in rocks, e. g. in geochemical standard reference materials and in meteorites. Iodine is measured in the mass spectrometer by producing negative I^– thermal ions using a rhenium double-filament ion source and a lanthanum salt as an auxiliary chemical for ionization. The long-lived radioactive ¹²⁹I is applied as a spike for the isotope dilution technique. The decomposition of the sample is carried out with hydrofluoric acid in a teflon bomb and iodine is isolated as AgI. By adding some drops of a sulfite solution, the isolation yield for this procedure is above 75% whereas a much less portion of the total iodide can only be isolated without this reducing agent. With this method different geochemical standards from the Centre de Recherches Pétrographiques et Géochimiques in Nancy as well as various Antarctic and non-Antarctic meteorites have been analysed. The iodine contents of these samples are in the range between some ng/g and some g/g. Relative standard deviations of 2–3% are obtained for contents above 100 ng/g. The detection limit is about 6 ng/g. The mass spectrometric analysis is a definitive method and opens the possibility to certify iodine traces in geochemical standards for the first time. Applying this method for the analysis of Antarctic meteorites, an iodine excess in some of these samples compared to the normal iodine concentration in non-Antarctic meteorites could be confirmed. Iodine contents in the higher ng/g level could also be analysed by an iodide-selective electrode in combination with an alkali fusion and a chromatographic separation of iodide. By using sulfite for reduction, isolation yields of about 85% could be obtained.

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Herrn Prof. Dr. K. H. Lieser zum 65. Geburtstag gewidmet

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Herrn Prof. Dr. L. Schultz, MPI Mainz danken wir für die Überlassung der Meteoritenproben, Herrn Dr. K. Govindaraju, Nancy für diejenige der geochemischen Standards. Im Zusammenhang mit der Untersuchung antarktischer Meteorite möchten wir die gute Zusammenarbeit mit Frau Dr. G. Dreibus, Herrn Prof. L. Schultz und Herrn Prof. H. Wänke vom MPI in Mainz hervorheben. Der Deutschen Forschungsgemeinschaft, die im Rahmen des Schwerpunktprogramms Antarktisforschung die Untersuchungen über Meteorite unterstützt hat, und dem Fonds der Chemischen Industrie danken wir für die finanzielle Hilfe.     

Comparative thermodynamic investigation of binary Ga-Bi system; Experimental determination of enthalpies of mixing and activity estimation for liquid Ga-Bi alloys

The results of experimental and analytical thermodynamic investigation of binary Ga-Bi system are presented in this paper. Integral molar enthalpies of mixing for liquid Ga-Bi alloys were obtained using quantitative differential thermal analysis. Activities of bismuth in the entire composition range and temperature interval 573-1073 K, were calculated by Zhang-Chous method for binary systems having two liquid or solid coexisting phases in combination with other Chous method developed for simple eutectic systems. Activities of gallium were derived from Gibbs-Duhem equation. Comparison between experimental, calculated values and existing literature data shows good agreement.     

Compton suppression neutron activation analysis: Past,present and future

Conclusions In this work a review of the development of compton suppression is presented. It was shown that the application of Compton-suppression counting in instrumental NAA reduces the detection limits and improves the accuracy for a list of elements by substantial reduction of the background of the -spectroscopy. Results for certified reference materials obtained through the use of Compton suppression are normally more accurate and in agreement with the published values. Compton suppression is particularly helpful for low level concentrations in environmental samples to those elements which exhibit severe special interferences in the normal NAA counting. A list of the elements with isotopes having single or close to single -ray decay schemes and which could benefit from Compton-suppression counting is presented. Also, evaluation is made regarding the reliability of Compton suppression with increase in the overall dead-time of the counting. It was concluded that this method does not provide accurate quantification of the isotopes when the overall dead-time exceeds the 10% range. Investigation of the natural background was performed with Compton suppression for the purpose of neutron activation analysis application. The method presented proves to broaden the application of NAA and helps in its competition for simplicity, accuracy and reliability with the modern methods of elemental analysis. Future application of coincidence spectrometry in activation analysis should include better enclosing of the primary detector, utiliza5tion of x-ray and well type detectors, -, -, and -- coincidence techniques.     

Multielement XRF Semimicroanalysis of Pb(Zr,Ti)O3 Type Ferroelectric Ceramic Materials Doped with Pb(Nb,Mn)O3 and Bi2O3 by the Thin Layer Method

A method of wavelength-dispersive XRF analysis of Pb(Zr,Ti)O₃ type ferroelectric ceramics doped with Pb(Nb,Mn)O₃ and Bi₂O₃ is presented. The major elements Pb, Zr, Ti and minor elements Nb, Mn, Bi were determined. Matrix effects were minimized by using the thin layer method. Standards of the same chemical composition but varied masses were prepared to simplify calibration. To minimize errors resulting from inhomogeneity of a mass per unit area, the internal standard was used. Preparation of the sample consisted in digesting 25mg of the materials (with nickel as the internal standard) in sulfuric acid, evaporating to dryness and digesting in nitric acid and hydrogen peroxide, filling up to 25mL, and dropping 0.5mL of the solution onto a substrate. Standard samples were prepared by dropping different amounts of the multielement solution onto the substrate. The residual standard deviation for the reference sample of mass from 0.25mg to 0.7mg was within the range of 0.001–0.009mg (correlation coefficient 0.998–0.999) for major elements and within the range of 0.00003–0.0009mg (correlation coefficient 0.989–0.993) for minor elements. The detection limits for 0.5mg samples were within the range of 0.015%–0.35% for manganese and zirconium, respectively.     

Uranium in coral skeletons determined by epithermal neutron activation analysis

A simple and non-destructive method has been proposed for the routine determination of uranium by epithermal neutron activation analysis in coral skeletons. Using a cadmium capsule, about 0.1-0.2 g samples were irradiated for 6 hours in the Triga Mark II Reactor. Measurements of -ray (²³⁹Np via ²³⁹U) were performed with each sample and standard after cooling for about three days. Compared with a non-destructive thermal NAA, the present method was found to improve the sensitivity because it reduced the intense Compton background induced by ²⁴Na. We determined uranium in coral standards within 2% of analytical precision. The data obtained for the carbonate standards are mostly consistent with reported values. The present method could be usefully applied to determine uranium contents in fossil corals from the Funafuti Atoll in the Pacific. The distribution of uranium between seawater and coral skeletons is also discussed in order to understand the environmental media in which the coral grew.     

Determination of boron in food and biological reference materials by neutron capture prompt-γ activation

Summary Boron concentrations were determined by in-beam neutron capture prompt- activation analysis for 31 food and biological reference materials prepared by the National Institute of Standards and Technology, Agriculture Canada, the National Institute for Environmental Studies of Japan, and the International Atomic Energy Agency. Sensitivity and background enhancements that are consequences of neutron scattering in hydrogenous matrices such as biological reference materials are discussed, as are correction methods for nuclide interferences, with emphasis on sodium. The limit of quantitation for these materials is 1.0–2.5 g/g and the limit of detection is 0.3–0.8 g/g, depending on the irradiation time. For materials with boron levels 30 g/g (e.g., most botanicals), the total analytical uncertainty is 2%.Temporary summer employment at the United States Food and Drug Administration, 200 C St., SW, Washington, DC 20204, USA