Decomposition of biological materials,rocks, and soils in pure oxygen under dynamic conditions for the determination of selenium at trace levels

Selenium is evolved from organic materials and from rocks and soils, after admixture with silicic acid and with silicic acid/cellulose, respectively, by combustion in oxygen under dynamic conditions in a special combustion apparatus. While concomitant elements that form sparingly volatile oxides remain in the ash on the sample holder, seleniun dioxide volatilizes and condenses on a cold finger, whence it is dissolved off with hydrochloric acid (1 + 1) or nitric acid (65% $\text{w}\text{v}$) by boiling under reflux. The isolated selenium is determined either by hydride-generation a.a.s. or by differential pulse cathodic stripping voltammetry. Detection limits for the overall procedures lie at 3 and 30 ng g^-1 respectively.     

The spectrographic determination of trace elements in rocks,minerals and soils

Summary The total content of trace elements in rocks, minerals and soils is determined by a semi-quantitativecathode layer arc spectrographic technique. For more accurate determinationsa variable internal standard technique, in which the trace element contents are compared with that of iron, is employed. This method is combined with a chemical concentration for the analysis of extracts of soils and plant materials. The chemical concentration technique involves the use of 8-hydroxyquinoline, tannic acid and thionalide, and gives recovery of microgram quantities of most trace elements, rejecting at the same time the alkalis, alkaline earths and phosphate.

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Zusammenfassung Der Gesamtgehalt von Spurenelementen in Gesteinen, Mineralien und Bodenproben wird nach einem halbquantitativen Verfahren bestimmt; hiezu werden die Proben in gehöhlten, als Kathoden geschalteten Elektroden im Bogenstrom verbrannt. Für genauere Bestimmungen wird nach einem abgeänderten Verfahren der quantitativen Spektralanalyse die Menge des Spurenelementes der Probe in Bezug auf ihren Eisengehalt ermittelt. Diese Methode ist mit einer chemischen Anreicherung für die Untersuchung von Bodenextrakten und Pflanzenmaterial kombiniert. Die Technik der chemischen Anreicherung beruht auf der Verwendung von 8-Oxichinolin, Gerbsäure und Thionalid; auf diese Weise lassen sich Mikrogramme der meisten Spurenelemente ermitteln, bei gleichzeitiger Abscheidung der Alkalien, Erdalkalien und Phosphate.

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Résumé La teneur globale des traces d'éléments dans les roches, les minéraux et les sols, est déterminée par une technique semi-quantitative, spectrographique d'arc à couche cathodique. Pour les dosages plus précis, on emploie une technique à étalon interne variable dans laquelle les teneurs en traces sont comparées à celles du fer. Cette méthode est combinée avec une concentration chimique pour l'analyse des extraits de sols et de végétaux. La technique de concentration chimique comporte l'emploi d'oxine, d'acide tannique et de thionalide et permet de récupérer des quantités de l'ordre du microgramme de la plupart des éléments en traces, ce qui élimine simultanément les alcalins, les alcalino-terreux et les phosphates.

     

Determination of trace elements in biological materials by neutron activation and extraction with TOPO

Solvent extraction with TOPO from 6M hydrochloric acid is proposed as a method for the elimination of interfering activities in neutron activation analysis of biological material for trace elements. By this procedure²⁴Na,⁴²K,³²P,⁸²Br, and⁴⁷Ca are efficiently removed, and a number of trace element activities can be measured by Ge(Li) spectrometry. Chemical yields are determined by re-activation. Data for Cu, Zn, Mo, and Cd in two biological standards are presented.     

Analytical evaluation of comparative data on trace elements in biological materials

Large bodies of data on a given material from different sources appear a major advantage of intercomparison experiments and a sound basis for a straight statistical evaluation (as is the usual approach in the assignment of recommended or consensus values). On closer inspection of the results, however, it is usually found that only one or two techniques are represented in statistically significant numbers, most frequently AAS and NAA, and their distribution may not be normal. Correct results are sometimes hidden among laboratory means in the lower or upper part of the frequency distribution plots. Conventional statistics neglecting procedural details and the chemistry behind a procedure may result in incorrect assignment from the reported data, which can be affected by unidentified systematic effects. Generally, in the lowest concentration range contamination predominates as the systematic error determining the accuracy of results. Activation analysis being the least vulnerable to this type of error, it is, if applicable, in principle the most likely to give correct answers. Follow-up work was carried out in this laboratory on the IAEA reference samples of Milk Powder A-11, Muscle Tissue H-4, Fish Flesh MA-A-2 and the Soil-5, clearly demonstrating the potential of activation analysis as verification technique. By determining the same element in the destructive and nondestructive mode, and on the basis of two different isotopes, virtually independent approaches are achieved, often allowing the disclosure of different types of errors. Results are also reported for nickel by a new voltammetric technique enabling its determination at the microgram per kilogram level.     

Speciation of trace elements in biological materials: trends and problems.

In the determination of trace elements in biological materials, speciation is of particular importance as the essential effects or toxicity of an element and its metabolic behaviour depend to a large extent on the chemical forms in which it is present in the organism. Speciation is relatively easy if a property of a particular compound can be measured directly in the sample without interference from the other components of the material, e.g., the enzymic activities of the metallo-enzymes. Another possibility for speciation is immunoassay, which likewise allows direct determination of a particular trace element. At present, however, with most trace elements both fractionation methods and analytical procedures have to be combined and speciation has to be carried out by determining the elemental content in the separated fractions. The methods and apparatus used in taking, storing and preparing the samples can, therefore, not be selected solely according to the requirements of trace element determination, but it is also essential to ensure that the biological structures of the components to be separated remain intact. In this work the need for speciation in the investigation of the toxic and essential effects of trace elements is shown with the help of some examples, and the problems that can occur in the various steps of sampling, storage and sample preparation are discussed.     

Radiochemical determination of some trace elements in biological materials using short-lived isotopes

A radiochemical procedure for the consecutive separation of vanadium and molybdenum, copper, manganese, rubidium and potassium is proposed for the analysis of biological materials. Vanadium and molybdenum are extracted together with 0.1% BPHA solution in toluene, copper followed by manganese are extracted as diethyldithio-carbamate complexes with chloroform and rubidium and potassium are precipitated as tetraphenylborates.     

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.     

Determination of trace elements in biological materials by instrumental epithermal neutron activation analysis

The use of reactor epithermal neutrons in instrumental activation analysis is described for the determination of trace elements via long-lived isotopes. A boron carbide filter is used. Results of analyses of human erythrocytes, plasma, urine and some biological reference materials are given to demonstrate the applicability of the method to biological samples. Bromine, iron, cesium, rubidium, selenium and zinc and cobalt are determined. The method provides accuracy and reliability similar to conventional thermal neutron activation but is faster. Limits of detection attainable with the two techniques are compared.     

Determination of trace elements in biological materials using tetramethylammonium hydroxide for sample preparation

A method to prepare milk powder, bovine liver and bovine muscle samples for analysis by electrothermal atomic absorption spectrometry (ETAAS) is proposed. Samples are mixed with a small amount of tetramethylammonium hydroxide (TMAH) and a stable and homogeneous slurry is produced in ca. 2 h with heating at 60–70 °C. After such sample preparation and dilution with water, trace elements are determined in certified reference materials. Pyrolysis and atomisation temperatures are optimised for each element, and several modifiers are investigated. External calibration is used for every analyte. Limits of detection (LODs), precision and accuracy are reported for Cd, Pb, Ni, Cr, Cu and Ag and compared with those obtained after conventional acid digestion. The main advantages of the proposed method are the simplicity of sample preparation and the longer lifetime of the graphite tube.     

Determination of trace elements in biological fluids

Main approaches to the trace element analysis of biological fluids and problems appearing in this case are considered. The specific character of these approaches is illustrated by the examples of the analysis of real samples for various trace elements. The advantage of methods for the direct determination of trace elements in these samples is demonstrated.     

An accurate procedure for multielement neutron activation analysis of trace elements in biological materials

A procedure for radiochemical neutron activation analysis of biological materials for As, Cd, Co, Cu, Ga, Hf, Mg, Mn, Na, Sb, Sc, Se, Zn, and the rare-earth elements (REE) has been developed. Maximum control over accuracy has been emphasized. Samples are digested under reflux in the presence of carrier for every element determined, and a chemical yield is measured for every element assayed. The procedure has been tested by replicate analysis of National Bureau of Standards bovine liver sample (SRM-1577). Values agree to within their uncertainties with those given by NBS for the 9 elements of this group that they have analyzed. Accuracies at the 90% confidence level for elements in the liver sample are estimated as better than ±10% for Cu, Na, and Zn, between ±10 and ±25% for As, Co, Hg, La, Mn, and Se, and between ±25 and ±50% for Cd, Sb, Sc, and Sm.     

Selective spectrographic determination of trace elements in pure copper

Summary For the determination of various trace elements with the globule-arc technique a method is used where individual shutters are employed in front of the film plane of the spectrograph. The shutters are automatically operated by a conventional tape reader. It permits to optimate the sensitivity in tracing various elements as the analytical lines are registered only at maximum vaporization and excitation. Further it is possible to eliminate coincidence of some lines by using one shutter for each element to be determined. In the analysis a 2m ARL grating spectrograph with photographic registration is used. A sample of 1 g is placed on a carrier electrode of copper. Graphite is used as counter electrode. The sample is melted in a 9 A continuous direct current arc. The total time of exposure is 240 s.

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Selektive spektrographische Bestimmung von Elementspuren in reinem Kupfer

Zusammenfassung Zur Bestimmung von Elementspuren in Kupfer mit der Kugelbogenmethode werden individuelle Blenden vor der Filmebene des Spektrographen verwendet, die automatisch durch ein konventionelles Lochstreifengerät gesteuert werden. Dadurch wird eine optimale Empfindlichkeit für jedes Element erzielt, da die Analysenlinien nur bei maximaler Verdampfung und Anregung aufgenommen werden. Außerdem werden Koinzidenzen vermieden, da für jedes Element eine Blende verwendet wird. Zur Anwendung kommt ein 2m ARL Gitterspektrograph mit photographischer Registrierung. Eine 1 g-Probe wird auf eine Trägerelektrode aus Kupfer gegeben, wobei Graphit als Gegenelektrode dient. Die Probe wird in einem kontinuierlichen Gleichstrombogen von 9 A geschmolzen. Die Gesamtbelichtungszeit beträgt 240 s.

     

Radiochemical separation of the trace elements As,Mo, Sb and Se from some biological standard reference materials

A radiochemical procedure for simultaneous determination of the trace elements As, Mo, Sb and Se after thermal neutron irradiation, based on destruction of the sample with saturated Mg/NO₃/₂ or oxygen combustion, followed by solvent extraction of each element from a common aliquot in 6M hydrochloric acid is deterials was analyzed and good agreement with certified values was obtained.The paper was presented in part at the 6th European Conference on Analytical Chemistry, Euroanalysis VI, Paris, September 1987.     

Very accurate,simultaneous determination of trace amounts of Co and Ni in biological materials by radiochemical neutron activation analysis

A very accurate and sensitive method for the simultaneous determination of trace amounts of Co and Ni in biological materials has been elaborated. The method is based on radiochemical neutron activation. Irradiation of samples in Cd-shielded channel of a nuclear reactor assures balanced activity ratio of⁵⁸Co and⁶⁰Co isotopes and favourable detection limits for both nickel and cobalt. Column chromatography (ion exchange and extraction) has been used for the quantitative and selective isolation of the determined radionuclides. High accuracy of the method has been demonstrated by the analysis of several certified reference materials.     

Decomposition of aminotetrazole based energetic materials under high heating rate conditions

A T-jump/time-of-flight mass spectrometer (T-Jump/TOFMS) is used to probe the decomposition of several aminotetrazole containing energetic materials under very high heating rates of 10(5)-10(6) K/s. The materials investigated are 5-amino-1-methyl-1H-tetrazolium dinitramide (MeHAT_DN), 1,5-diamino-4-methyl-1H-tetrazolium dinitramide (MeDAT_DN), 1,5-diamino-1H-tetrazolium nitrate (DAT_N), 1,5-diamino-4-methyl-1H-tetrazolium azide (MeDAT_N3), and 5-aminotetrazolium dinitramide (HAT_DN). Subtle differences between materials in functional group placement and anion composition allow for further understanding of the decomposition pathway of the tetrazole structure and various anions. Two decomposition pathways for the tetrazole ring are observed, which result in the primary formation of HN(3) or N(2). The N(2) formation pathway occurs when functional groups are placed symmetrically around the tetrazole ring, whereas asymmetric placement results in HN(3) production. The differing anion compositions also show effects on thermal stability of the salts, as is demonstrated by a lower decomposition temperature for the azide containing salt compared to the similar dinitramide containing material. For the decomposition of the dinitramide molecule, high temperature (N(2)O forming) and low temperature (NO(2) forming) decomposition pathways are observed, as has been previously suggested.     

Determination of trace elements in Brazilian rice grains and in biological reference materials by neutron activation analysis

Instrumental neutron activation analysis was applied to the determination of the elements Na, K, Br, As, Rb, Zn, Co, Fe and Sc in Brazilian rice samples and in biological standards. Hg and Se concentrations were determined by using a simple radiochemical separation. The chemical procedure was carried out by means of distillation of Hg and Se in HBr medium and subsequent precipitation of selenium by sodium metabisulfite and mercury by thioacetamide. The accuracy of the instrumental and radiochemical methods was evaluated by means of analysis of the Reference Materials NBS-Bovine Liver, Bowen's Kale and NBS-Rice Flour.     

Determination of trace elements in crude oils and organic materials extracted from oil-forming source rocks in China by INAA

A combination of Soxhlet extraction, column chromatography and INAA with GC and GC-MS was used in this work for the study of the abundance patterns of 36 trace elements and their correlation in nearly 100 samples of crude oil and organic materials extracted from oil-forming source rocks from 10 main Chinese oilfields. The low V/Ni ratios of 0.01 to 0.3 state the oil-forming continent environment. The geochemical significance hinted from other trace element abundances is also briefly discussed.     

Determination of some additional trace elements in certified standard reference materials (soils, sludges, sediment) by ICP-emission spectrometry

Summary The concentration of some additional elements like Ag, Au, B, Ba, Be, Co, Li, Mo, Na, P, Pt, and S in some standard reference materials (SRM's) were determined by using high resolution ICP (Inductively Coupled Plasma)-emission spectrometry. The materials used were three soils and three sludges from the BCR (Community Bureau of Reference, European Communities) and one sediment from NBS (National Bureau of Standards, USA). The aqua regia soluble and the total content using HF-treatment were shown. The given results are the mean values of 6 independent measurements for each material and for each decomposition method (certification conditions). The quantitative determination of Au and Pt was not possible due to severe spectroscopic interferences, which could not be eliminated. Beside the concentration values also the measured detection limits and the limits of determination for each element in the matrices under investigation are given. For comparison and for testing the validity of the decomposition procedures, also certified elements like Cd, Cu, Ni and Zn have been analysed in all the samples.

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Bestimmung einiger zusätzlicher Spurenelemente in zertifizierten Referenzmaterialien (Boden, Schlamm, Sediment) durch ICP-Emissions-Spektrometrie