Determination of lead, cadmium, copper and zinc in human tissues by differential pulse anodic stripping voltammetry

Summary A convenient electroanalytical technique for the simultaneous determination of lead, cadmium, copper and zinc in human blood and teeth is described. The method is based on differential pulse anodic stripping voltammetry at the static mercury drop electrode (SMDE). Optimum conditions for the anodic stripping of Pb, Cd, Cu and Zn were determined using ammonium acetate and dilute nitric acid (pH 2) as electrolytes. Interferences from other metals were not observed and the estimations were reproducible within a standard deviation of±4%. Low blank values and high sensitivity of the method allowed the determinations at sub-ppb levels with an electrolysis time of 1–3 min. The accuracy of the method has been tested by comparison with the results obtained by mass spectrometry and atomic absorption spectrometry. The results and findings are discussed in brief.

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Bestimmung von Blei, Cadmium, Kupfer und Zink in menschlichen Geweben mit Hilfe der Differentialpuls-Anodic Stripping Voltammetrie

Zusammenfassung Eine vorteilhafte elektroanalytische Methode zur Bestimmung von Pb, Cd, Cu und Zn in menschlichem Blut und in Zähnen wird beschrieben. Das Verfahren beruht auf der Differentialpuls-Anodic Stripping Voltammetrie an der statischen Quecksilbertropfelektrode. Mit Hilfe von Ammoniumacetat und verdünnter Salpetersäure (pH 2) als Trägerelektrolyten wurden die optimalen Bedingungen ausgearbeitet. Störungen durch andere Metalle wurden nicht beobachtet. Die Standardabweichung betrug ±4%. Infolge der niedrigen Blindwerte und der hohen Empfindlichkeit konnten Bestimmungen im Sub-ppb-Bereich mit Elektrolysezeiten von 1–3 min durchgeführt werden. Die Genauigkeit der Methode wurde durch Vergleich mit massenspektrometrischen und AAS-Untersuchungen bewiesen. Die Ergebnisse werden kurz diskutiert.

     

A minimum covariance basis for diatomic vibrational constants

An alternative semianalytical representation of diatomic vibrational energy levels to the Dunham expansion, is presented in the form of an expansion over Newton polynomials. This latter representation produces smaller variances and correlation coefficients than Dunham's representation, especially for light molecules. The method is illustrated by application to the vibrational levels of the ground state of the H₂ molecule. Extension of the method to vibrational-rotational levels is discussed briefly.     

Rubidium uranium trisulphate: A new chemical assay standard for uranium

Rubidium uranium trisulphate [Rb₂U(SO₄)₃] was prepared as a high purity compound of uranium in different lots of 250 g each. The compound was characterised and evaluated by chemical, atomic spectrosopic, infrared, X-ray diffraction and thermogravimetric methods for its use as a chemical assay standard for uranium. The compound is stoichiometric, pure, homogeneous and stable in atmospheric conditions. The solubility studies showed that Rb₂U(SO₄)₃ is easily soluble in mineral acids. An experiment based on Randomised Block Design was carried out to assign a value to the uranium content in Rb₂U(SO₄)₃ from the statistically analysed chemical data. The assigned value of [34.167±0.042]% to the uranium content is in close agreement with the theoretical value of 34.152%. Based on these studies, Rb₂U(SO₄)₃ is recommended as a chemical assay standard for uranium.     

Enantiomeric separation of a melatonin agonist Ramelteon using amylose-based chiral stationary phase

A new simple isocratic chiral liquid chromatographic method was developed for the enantiomeric purity of Ramelteon[(S)-N-[2-(1,6,7,8-tetrahydro-2H-indeno[5,4-b]furan-8-yl) ethyl]-propionamide], a melatonin agonist in bulk drugs. The chromatographic separation was achieved on Chiralpak AD-H, 250 mm × 4.6 mm, 5 μm column using a mobile phase system consisting of n-hexane, ethanol and methanesulfonic acid in the ratio of 900:100:0.1 (v/v/v). The mobile phase was pumped on the column at the flow rate of 1 mL min^?1. Addition of methane sulfonic acid in the mobile phase enhanced chromatographic efficiency and resolution between the enantiomers. The resolution between the enantiomers was found to be more than four. The developed method was subsequently validated and proved to be accurate and precise. The experimentally established limit of detection and quantification of (R)-enantiomer were found to be 25.5 and 77.2 ng ml^?1, respectively, for 20 μl injection volumes. The percentage recovery of (R)-enantiomer was ranged from 98.5 to 101.9 in bulk drug samples of Ramelteon. The stability of Ramelteon sample in analytical solution was checked for about 48 h at room temperature and was found to be stable for about 48 h. The proposed method was found to be suitable and accurate for the quantitative determination of (R)-enantiomer in drug substance.     

Path integration of a Lagrangian related to an electron gas in a random potential

Path integration of a Lagrangian related to an electron gas in a random potential is carried out within the framework of Feynman's polygonal approach. The integration is direct and does not require the knowledge of an auxiliary measure or the artificial coupling of the system to external forces.     

Determination of short-lived radionuclides in fresh fall-out debris for identification of nuclear weapon tests

Radiochemical procedures for the assay of short-lived fission and activation products are described. They are rapid and quantitative and the radionuclides separated are radiochemically pure. Ratios of some of the short-lived radionuclides obtained by these measurements for selected Chinese and French nuclear tests are given and provide information about the fissile material used in the tests.     

Path integration of a quadratic action with a generalized memory

Path integration of an action representing a harmonic oscillator with a generalized memory is carried out within the framework of Feynman's polygonal approach. The exact propagator obtained is in the form of an exponential integral over a single variable. Closed analytical results are available for special cases of the memory function.