Mass spectrometric determination of cadmium in i.a.e.a. fish solubles

The cadmium content of the I.A.E.A Fish Solubles [A-6 (1975)] was determined by the isotope dilution method. After dry-ashing and dissolution of the specimen, the cadmium was equilibrated with a known amount of ¹⁰³Cd spike, isolated by ion exchange, purified by dithizone extraction, and converted to the sulfide form in 1% H₃PO₄ solution. The CdS precipitate was loaded onto a baked single rhenium filament for mass spectrometric analysis. The ¹⁰³Cd/¹¹⁰Cd ratio was measured to compute the cadmium content of 0.278 ± 0.032 ppm (dry weight basis) in the Fish Solubles.     

Absorbance(a.Intensity(a.u.)

正the XAS is a bulk characterization rather than a sur‐face‐sensitive tool. The penetration depth is a function of X‐ray attenuation coefficient of the material at the relevant incident X‐ray energy, it is about 5–10 mm when measuring the LIII edge of Ce at around 6 keV [51,52]. Recently, Schmitt et al. [20] re‐viewed the XAS study on the defect structure and chemistry in ceria and its solution. Herein, we just survey this tool used for characterization of reduced ceria powder as a catalyst.In a partially reduced ceria, the XANES part of X‐ray absorp‐tion spectrum for the Ce LIII edge can be used to quantify Ce3+and Ce4+ valence states to study the effect of particle size, do‐     

N.m.r. studies of a rate process in a bridged biphenyl: Resolution of a discrepancy between n.m.r. and polarimetric kinetic data

Total bandshape analysis of the temperature-dependent n.m.r. spectrum of the bridge methylene protons in 6,6-dicarbethoxy-1,2,3,4-dibenzcyclohepta-1,3-diene has been carried out to yield the following activation parameters: ΔG = 60.96 ± 0.17 kJmol^?1 (14.57 ± 0.04 kcal mol^?1), ΔH^? = 47.3 ± 0.8 kJ mol^?1 (11.3 ± 0.2 kcal mol^?1) and ΔS^? = ?45.6 ± 3.3 J mol^?1 K^?1 (?10.9 ± 0.8 cal mol^?1 K^?1). A value of ΔG^? in agreement with the above may be obtained from a bandshape analysis (at a suitable temperature) of the spectrum of the methylene protons in the carbethoxy groups. In our opinion, the rate process described by these activation parameters must be the configurational inversion of the biphenyl system, and thus the polarimetric data on this compound reported by Iffland and Siegel [J. Am. Chem. Soc. 80, 1947 (1958); half-life of 80 min at room temperature] are seriously called to question, as previously noted by Sutherland and Ramsay [Tetrahedron 21, 3401 (1965)]. We have attempted unsuccessfully to repeat the polarimetric work, and have been able to show by means of thin-layer chromatography in the cold, mass spectral analysis and polarimetry that an optically active impurity (as yet unidentified) is the most probable cause of the discrepancy.     

Analytical application of second-harmonic a.c. polarography

Phase-selective second-harmonic a.c. polarography can be used to distinguish two different species having similar reduction potentials. Because each species has a different phase angle depending on the electrode kinetics, a certain phase angle can be chosen to detect only one component in the mixture. In 1 M potassium chloride solution, indium-(III) at the 4 × 10^-6 M level can be determined in the presence of 50-fold amounts of cadmium(II), and zinc(II) at the 2 × 10^-5 M level in the presence of 100-fold amounts of nickel(II).     

Anodic a.c. polarography of methylthymol blue

The anodic a.c. polarographic properties of methylthymol blue (MTB) were investigated in the supporting electrolyte of potassium nitrate containing buffer. The difference in the peak potentials of MTB and EDTA is a good measure of the difference in the stabilities of both chelates. The stability constant of mercury(II)-MTB complex was successfully determined on the basis of that reported for the mercury(II)-EDTA complex.     

Synthesis of a teichoic acid fragment of bacillus var.niger w.m. by a phosphotriester approach

Three properly-protected derivatives, one non-terminal and two terminal units, of 3-0-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-sn-glycerol have been joined together by two interglyceridic (2→1) phosphotriester linkages to afford, after removal of all protective groups, a teichoic acid fragment.     

Diagrammatic kinetic theory for a lattice model of a liquid. I. Theory

We present a diagrammatic formalism for the time correlation functions of density fluctuations for an excluded volume lattice gas on a simple d-dimensional hypercubic lattice. We consider a multicomponent system in which particles of different species can have different transition rates. Our theoretical approach uses a Hilbert space formalism for the time dependent dynamical variables of a stochastic process that satisfies the detailed balance condition. We construct a Liouville matrix consistent with the dynamics of the model to calculate both the equation of motion for multipoint densities in configuration space and the interactions in the diagrammatic theory. A Boley basis of fluctuation vectors for the Hilbert space is used to develop two formally exact diagrammatic series for the time correlation functions. These theoretical techniques are generalizations of methods previously used for spin systems and atomic liquids, and they are generalizable to more complex lattice models of liquids such as a lattice gas with attractive interactions or polymer models. We use our formalism to construct approximate kinetic theories for the van Hove correlation and self-correlation function. The most simple approximation is the mean field approximation, which is exact for the van Hove correlation function of a one component system but an approximation for the self-correlation function. We use our first diagrammatic series to derive a two site multiple scattering approximation that gives a simple analytic expression for the spatial Fourier transform of the self-correlation function. We employ our second diagrammatic series to derive a simple mode coupling type approximation that provides a system of equations that can be solved for the self-correlation function.     

Biomimetic approach to communesin B (a.k.a. nomofungin)

The development of an approach to the alkaloid communesin B (2) is presented. The approach is based on considerations of a possible biosynthetic sequence involving an oxidative coupling of tryptamine with a derivative of the ergot alkaloid aurantioclavine. Structure revision is also suggested for the recently isolated microfilament disrupting alkaloid nomofungin.     

Fast sweep a.c. polarography

Summary The design of a fast sweep a.c. polarograph suitable for recording second harmonic and intermodulation polarograms is described. The instrument was found suitable for determining reducible species down to concentrations of approximately 2×10^–7 M. By integrating the faradaic response a considerable improvement in precision can be obtained.

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Fast-Sweep-Wechselstrompolarographie

Zusammenfassung Ein Polarograph wird beschrieben, der zur Aufnahme von Polarogrammen mit Hilfe der 2. Harmonischen und der Zwischenmodulation geeignet ist. Reduzierbare Substanzen können bis herab zu 2 · 10^–7 M erfaßt werden. Durch Integration des Faradaystroms kann eine beträchtliche Verbesserung der Genauigkeit erreicht werden.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9.1972 in Heidelberg, Germany.