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PubMed1996

Photochemical Synthesis of (eta(6)-Arene)chromium Hydrido Stannyl and (eta(6)-Arene)chromium Bis(stannyl) Complexes.

Photolysis of (eta(6)-arene)Cr(CO)(3) complexes and HSnPh(3) in aromatic solvents at room temperature has led to two classes of complexes: hydrido stannyl compounds containing the eta(2)-H-SnPh(3) ligand and bis(stannyl) compounds containing two SnPh(3) ligands. The ratio between the two complexes simultaneously produced depends on the choice of the arene. Complexes with different arenes (mesitylene, toluene, benzene, fluorobenzene, and difluorobenzene) have been obtained and characterized including X-ray structures for (eta(6)-C(6)H(3)(CH(3))(3))Cr(CO)(2)(H)(SnPh(3)) (1a), (eta(6)-C(6)H(3)(CH(3))(3))Cr(CO)(2)(SnPh(3))(2) (1b), (eta(6)-C(6)H(5)F)Cr(CO)(2)(SnPh(3))(2) (4b), and (eta(6)-C(6)H(4)F(2))Cr(CO)(2)(SnPh(3))(2) (5b). X-ray crystallography of the last three compounds has given the following results: 1b, monoclinic, space group P2(1)/c (No. 14), a = 13.905(4) Å, b = 18.499(2) Å, c = 17.708(2) Å, Z = 4, V = 4285(1) Å(3); 4b, orthorhombic, space group Pca2(1) (No. 29), a = 16.717(2) Å, b = 18.453(2) Å, c = 25.766(2) Å, Z = 8, V = 7948(2) Å(3); 5b, monoclinic, space group P2(1)/c (No. 14), a = 13.756(2) Å, b = 18.560(2) Å, c = 17.159(2) Å, Z = 4, V = 4372(2) Å(3). The relatively high J((119)Sn-Cr-H) and J((117)Sn-Cr-H) values as well as the X-ray structural data provide evidence for the existence of three-center two-electron bonds in the hydrido stannyl complexes. The (1)H NMR data of the complexes are compared with chromium-arene bond distances, and a sensible trend is observed and discussed.

Journal Article↗
PubMed2003

Specific extraction of chromium as tetrabutylammonium-chromate and spectrophotometric determination by diphenylcarbazide: speciation of chromium in effluent streams.

A very specific, selective, simple, and inexpensive procedure was developed for the speciation of CrVI and CrIII. This method is based on the quantitative extraction of chromate and CrIII (previously oxidized to CrVI) as a tetrabutylammonium-chromate ion-pair in methyl isobutyl ketone (MIBK), and then back extraction and preconcentration with an acidic diphenylcarbazide (DPC) solution. Back extraction was applied to achieve further preconcentration by a final factor of 20. The CrVI-DPC complex was determined in back-extract by a spectrophotometer at 548 nm. Under these extraction conditions, most of the probable concomitant cations and anions remained in the first inorganic phase. The calibration curve was linear up to 0.14 microg L(-1) of CrVI with a detection limit of 2.22 ng L(-1). The developed procedure was found to be suitable for the determination of the CrVI and CrIII species in various natural water samples with a relative standard deviation of better than 1.6%. The method was successfully applied to the speciation of chromium in spiked natural water samples, and also samples of effluent from a leather treatment plant.

Journal Article↗
PubMed2002

Hard X-ray microprobe studies of chromium(VI)-treated V79 Chinese hamster lung cells: intracellular mapping of the biotransformation products of a chromium carcinogen.

The uptake of carcinogenic and mutagenic Cr compounds and the intracellular distribution of their biotransformation products in V79 Chinese hamster lung cells were studied by synchrotron-radiation-induced X-ray emission (SRIXE). SRIXE analysis was performed on whole cells that had been treated with either Cr(III) or Cr(V) 1,10-phenanthroline complexes, or Cr(VI). The high spatial resolution (0.3 microm) and elemental sensitivity (~10(-15) g Cr/cell) of the technique provided detailed maps of Cr and other cellular elements in thin sections prepared from Cr(VI)-treated cells. The Cr carcinogen concentrated in P-rich regions corresponding to the nucleus, as well as other areas of the cell that are likely to correspond to organelles. This is the first study that has enabled the determination of the localization of the biotransformation products of Cr(VI) carcinogens in a target lung cell.

Animals↗
PubMed1987

Anion-exchange high-performance liquid chromatography of water-soluble chromium (VI) and chromium (III) complexes in biological materials.

A high-performance anion-exchange liquid chromatograph coupled to visible-range (370 nm) and UV (280 nm) detectors and an atomic-absorption spectrometer allowed the rapid determination of CrVI and/or complexes of CrIII in rat plasma, erythrocyte lysate and liver supernatant treated with CrVI or CrIII in vitro. CrVI in the eluates was determined using both the visible-range detector and atomic-absorption spectrometer (AAS). The detection limits of CrVI in standard solutions using these methods were 2 and 5 ng (signal-to-noise ratio = 2), respectively. Separations of the biological components and of CrIII complexes were monitored by UV and AAS analyses, respectively. Time-related decreases of CrVI accompanied by increases in CrIII complexes were observed, indicating the reduction of CrVI by some of the biological components. The reduction rates were considerably higher in the liver supernatant and erythrocyte lysate than in the plasma. These results indicate that the anion-exchange high-performance liquid chromatographic system is useful for simultaneous determination of CrVI and CrIII complexes in biological materials.

Animals↗
PubMed1985

The effects of inorganic chromium and brewer's yeast on glucose tolerance, plasma lipids, and plasma chromium in elderly subjects.

Twenty-three healthy, well-nourished, free-living elderly volunteers were given daily, for 10 wk, 5 g brewer's yeast, 200 micrograms Cr3+ as chromic chloride (CrCl3), or placebo. There were no significant changes in glucose tolerance, insulin, cholesterol or triglycerides after supplementation in any of the three groups. Plasma Cr3+ rose significantly after supplementation with CrCl3 but did not change after yeast or placebo supplementation. Plasma Cr3+ did not increase after an oral glucose load and did not correlate with glucose, insulin or lipid values in any of the groups. Calculated intakes of eight indicator nutrients were well above 100% of the RDA except for calcium. These healthy elderly persons, eating nutritious diets, are not at risk for Cr3+ deficiency as measured by the absence of a clinical response to CrCl3 or brewer's yeast supplementation. This study suggests that age per se is not a factor leading to Cr deficiency.

Aged↗
PubMed2003

[Determination of chromium(III) and chromium(VI) in water using flow injection on-line preconcentration and separation with flame absorption spectrometric detection].

A rapid and sensitive method for the sequential determination of Cr(III) and Cr(VI) in water samples based on flow injection on-line preconcentration and separation with two-microcolumn system-flame atomic absorption spectrometry has been developed. The Cr(III) and Cr(VI) in water samples were respectively retained in a microcolum with cation exchange resin and in a microcolumn with anion exchange resin and were eluted directly by 15% HNO3 and 8% NH4NO3, respectively. The characteristic concentrations (pre-concentration time of 1 min) for Cr(III) and Cr(VI) were 1.50 micrograms.L-1 and 1.39 micrograms.L-1, respectively, The relative standard deviations at 10 micrograms.L-1 level were 3.41% and 1.80%, and the corresponding detection limits (3 sigma) were 1.03 micrograms.L-1 and 0.54 microgram.L-1, respectively. The satisfactory recovery of 93.48%-107.5% could be obtained from water samples.

Chromium↗
PubMed1994

Low-frequency EPR detection of chromium(V) formation by chromium(VI) reduction in whole live mice.

Measurements by direct low frequency EPR spectroscopy provide the first evidence that Cr(V) is generated in one-electron reduction of Cr(VI) in live mice. The Cr(V) yield reached a maximum about 10 min following Cr(VI) intravenous injection and then decayed slowly with a life time of approximately 37 min. The time for the Cr(V) EPR signal to reach maximum intensity increased with the dose of Cr(VI). A discernible EPR signal was still observable at a dose as low as 0.1 mmol/kg. The Cr(V) was found predominantly in the liver, with a small amount in the blood. No Cr(V) signal was detectable in heart, spleen, kidney, and lung. Pretreatment of the animals with metal ion chelators, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and 1,10-phenanthroline significantly reduced the intensity of the Cr(V) signal that was observed.

Animals↗
PubMed1995

Low-frequency EPR study of chromium(V) formation from chromium(VI) in living plants.

The reduction of Cr(VI) by green algae and higher plants was investigated using a low-frequency EPR spectrometer equipped with an extended loop gap resonator. Incubation of algae (Spirogyra and Mougeotia) with Cr(VI) generated both Cr(V) and Cr(III). The maximum Cr(V) signal was observed in about 10 minutes. Incubation of Cr(VI) with oat, soybean, and garlic generated Cr(V). The maximum Cr(V) peak appeared after more than 10 hours of incubation, and Cr(V) was located predominantly in the roots. The Cr(V) peak exhibited hyperfine splittings of about 0.79 gauss, typical of the Cr(V) complexes with diol-containing molecules. The results suggest that the reduction of Cr(VI) to lower oxidation states by living plants may provide a detoxification pathway for Cr(VI) in ecological systems. The results also indicate that low-frequency EPR may be used to investigate the metabolism of paramagnetic metal ions in intact plants.

Chlorophyta↗