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At least 1,045 records · Page 58Linked to original sources
PubMed1989

Determination of serum nickel by graphite furnace atomic absorption spectrometry with Zeeman-effect background correction: values in a normal population and a population undergoing dialysis.

An atomic absorption spectrometric method with Zeeman-effect background correction for the determination of nickel, which requires only serum dilution with an aqueous surfactant, is described. The average nickel concentration in sera collected from 38 healthy adult volunteers was 0.14 +/- 0.09 micrograms l-1 of Ni, which is approximately four times lower than normals reported previously (0.65 +/- 0.35 or 0.46 +/- 0.26 microgram l-1 of Ni). The procedure yielded accurate results for the analysis of three different reference serum pools. A comparison of the average nickel concentrations from a patient population undergoing regular haemodialysis with our normal population showed that the average concentration of serum nickel in the dialysis patient group (n = 27 patients) was 46 times higher than normal (6.38 +/- 3.36 micrograms l-1 of Ni; n = 40 specimens).

Adult↗
PubMed2004

Hydrogen bond directed self-assembly of core-substituted naphthalene bisimides with melamines in solution and at the graphite interface.

A series of red and blue highly fluorescent core-substituted naphthalene bisimide dyes has been synthesized and they have been investigated as supramolecular building blocks. NMR and UV-Vis titration experiments of these dyes with complementary melamines revealed the formation of triple hydrogen bonds (DAD-ADA arrays) in solution. At stoichiometric ratios, ditopic melamine receptors could dissolve otherwise insoluble bisimides by means of hydrogen bonding, even in aliphatic solvents. At the solution/graphite interface, one-dimensional chains of hydrogen bonded naphthalene bisimides and two-dimensional adlayers of ditopic melamines are formed for the pure compounds but little evidence for heterocomplexes between the two complementary building blocks could be obtained.

Journal Article↗
PubMed2005

Theoretical study of the reactivity of cesium with benzene and graphitic C(x)H(y) clusters.

The adsorption of a Cs atom on planar (C6H6 and C24H12) and nonplanar (C20H10 and C21H9) carbon clusters has been studied using the density-functional theory, with the local-density approximation and atomic pseudopotentials. Binding energies as a function of separation have been calculated for several configurations of the Cs atom on the different substrates. The adsorption on sites above the center of carbon rings is more stable than adsorption on top of carbon atoms and C-C bonds. In the case of the curved clusters, adsorption on the concave side is preferred compared to the convex side. The Cs bonding is stronger on the nonplanar clusters. The strength of the binding energy depends on two effects: the magnitude of the highest occupied molecular orbital-lowest unoccupied molecular orbital (LUMO) energy gap of the substrate, and the energy of the valence state of Cs relative to the LUMO of the substrate. Due to a favorable relative position of those two energy levels, charge transfer occurs from Cs to the two nonplanar clusters, and this provides an ionic contribution to the bonding. The analysis of the electronic density redistribution and of the local Fukui functions helps in the interpretation of the charge transfer and the reactivity.

Journal Article↗
PubMedDate not supplied

Determination of thallium in urine with Zeeman effect graphite furnace atomic absorption.

Thallium is determined in urine with a simple dilution as the only sample pretreatment. Zeeman effect background correction provides adequate accommodation for non-atomic absorption such that sufficient diluted urine can be introduced into the furnace to achieve a detection limit of 0.5 ng/mL. Precision and accuracy were evaluated with Environmental Protection Agency water samples and in vitro spiked urine pools; precision of 15% at the 6 ng/mL level was observed. Diluted urine was used in calibration, with only 4 to 5% difference in slope observed within run among randomly selected urine specimens.

Humans↗