Preliminary studies on arsenic species in some environmental samples

Arsenic compounds have been determined in some environmental samples from the German Environmental Specimen Bank (ESB) (marine mussels, freshwater mussel and fish, sea-gull eggs) and certified reference materials (DORM-1, DOLT-1, NBS Oyster Tissue) after separation by open column cation and anion exchange chromatography by two different methods of total arsenic determination in separated fractions (instrumental neutron activation analysis or hydride generation atomic absorption spectrometry). Arsenobetaine has been identified as the major species in all the different materials.     

LEMS: application of the method to study the static quadrupole moment of the isomer in 179W

The method of the level mixing spectroscopy (LEMS) was applied for the first time for the study of the static quadrupole moments of high-K isomers in the A ≈ 180 mass region. Results from a preliminary experiment for the static quadrupole moment of the (750 ns) isomer in ¹⁷⁹W give a limit for its upper value Q < 7b, corresponding to a quadrupole deformation of β2< 0.343.     

The vanadium content of human dental enamel and its relationship to caries

A method for the determination of vanadium in dental enamel based on neutron activation analysis is described. After rapid dissolution of the irradiated sample in perchloric acid,⁵²V is quickly separated by solvent extraction from mixed perchloric-hydrochloric medium with N-benzoyl-N-phenyl hydroxylamine (BPHA) reagent in toluene in 95% yield. The technique was applied to samples from a low caries area of Dalmatia, Zemunik (DMFT<2), and a normal area, Novigrad (DMFT>5), in the same region. No significant differences in vanadium content were found between the two areas, nor between deciduous and permanent teeth. The levels in other areas of Yugoslavia were found to be similar, with a mean concentration of 3.7±1.5 ng·g⁻¹ for 37 samples, with a nearly normal distribution; a few impacted teeth gave lower values. The method can also be adapted to the analysis of bone and biological materials generally.     

Evaluation of the CuCl+ stability constant and molar absorptivity in aqueous media

Upper and lower bound estimates of the CuCl⁺ stability constants produced by various investigations have been quantitatively examined. Our analyses, including our own ultraviolet spectroscopic investigations, indicate that the CuCl⁺ stability constant in 1 molar HClO₄ is β₁=0.70±0.23. The CuCl⁺ molar absorptivity at a wavelength of 250 nm was determined as 1860 cm²-mol^?1. Our analyses suggest the bound β ₁ ^′≤0.37 for the formation constant of MgCl⁺ at one molar ionic strength.     

Measured gyromagnetic ratios of individual excited states in the ground- and gamma-bands of166Er

The gyromagnetic ratios of levels up to the 10 ₁ ⁺ in the ground-state band and of the 2 ₂ ⁺ state in theγ-band of¹⁶⁶Er were simultaneously determined experimentally by means of the thin-foil, perturbedγ-ray angular distribution technique utilizing the transient hyperfine field manifest at nuclei of Er ions rapidly traversing polarized Fe. Beams of 220- and 160-MeV⁵⁸Ni projectiles were used to Coulomb excite the levels of interest. The present results are compared with the spin-dependencies ofg-factors of levels in the ground-band predicted by recent cranked Hartree-Fock-Bogoliubov calculations and with interacting boson model expectations which includeg-boson effects.     

Construction of a compact spectrofluorometer/spectrophotometer system using a flexible liquid core waveguide

A liquid-core waveguide made of Teflon AF-2400 has been used to construct a simple, sensitive and robust instrument capable of performing fluorimetric and spectrophotometric analyses on aqueous solutions. The instrument, which uses a CCD array detection system, is unique in that high performance is achieved for both measurement techniques with minimal changes in instrument configuration. The fluorimetric detection limits for quinine sulfate and chlorophyll-a are 0.06 nanomolar and 0.03 nanomolar, respectively. Absorbance measurements using the same instrument demonstrate nanomolar detection capacities for hydrogen sulfide and subnanomolar detection limits for methylene blue.     

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.     

On processing standards in radiochemical neutron activation analysis

In radiochemical neutron activation analysis, standards may be measured directly or subjected to the same radiochemical processing as the sample. Some considerations in regard to processing are examined, and the advantages and disadvantages of this approach discussed. It is concluded that processing of standards is often inadvisable and can lead to errors, particularly if used as a substitute for radiochemical yield determinations.     

Trace heavy metals in various Yugoslav tobaccos

Summary Levels of trace heavy metals in various kinds of tobacco are poorly studied, so their determination in this matrix is important both from the point of view of health studies connected with smoking and more general aspects of the uptake of trace elements by plants. Because of its great sensitivity, neutron-activation analysis is very suitable for determination of trace heavy metals. The great range of concentrations to be expected makes non-destructive analysis less suitable. Thus As, Cd, Cu, Hg, Mn, Sb, Se, U, V and Zn were determined by means of rapid radiochemical separations and measurement of the-ray spectra of the isolated radionuclides with an NaI detector. Iron, and manganese at higher levels, was determined spectrophotometrically. The accuracy of the results, which represent the mean value of at least two measurements for about 10 varieties of Yugoslav tobacco, was checked by the analysis of various standard reference materials and good agreement were obtained with certified or literature values. The results were compared with analyses of Kentucky IR-1 tobacco.

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Zusammenfassung Die Schwermetallspuren in verschiedenen Tabaksorten wurden bisher nur wenig untersucht. Deren Bestimmung ist sowohl für Fragen der Gesundheit der Raucher wie im allgemeinen hinsichtlich der Spurenelementaufnahme durch Pflanzen von Bedeutung. Die Neutronenaktivierungsanalyse ist für die Bestimmung von Schwermetallspuren ihrer hohen Empfindlichkeit wegen sehr geeignet. Die weiten Konzentrationsgrenzen, mit denen zu rechnen ist, lassen nicht-destruktive Analysenverfahren weniger geeignet erscheinen. Daher wurden As, Cd, Cu, Hg, Mn, Sb, Se, U, V und Zn radiochemisch rasch abgetrennt und die Gammaspektren der isolierten Radionuklide mit einem NaJ-Detektor bestimmt. Größere Mengen Eisen und Mangan wurden spektrophotometrisch bestimmt. Die Genauigkeit der Ergebnisse, die ihrerseits den Durchschnittswert von wenigstens zwei Messungen bei ungefähr 10 jugoslawischen Tabaksorten darstellen, wurde durch Vergleich mit verschiedenen Standardproben geprüft. Dabei wurde gute Übereinstimmung mit gesicherten Werten bzw. Literaturangaben erzielt. Die Resultate wurden mit Analysenwerten von Kentucky-IR-1-Tabak verglichen.

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Paper presented at the International Symposium on Microchemical Techniques, Davos, May 1977.