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PubMed2002

Chemically facilitated chromium(VI) transport throughout an anion-exchange membrane application to an optical sensor for chromium(VI) monitoring.

The Raipore R1030 membrane, an anion-exchange membrane containing ammonium groups as ionogenic groups, was evaluated as the interface of an optical sensor for Cr(VI), and the effect of chemical parameters affecting Cr(VI) transport were studied. Good transport features were obtained, demonstrating the suitability of the Raipore R1030 membrane for this application. Thus, an optical sensor for chromium(VI) monitoring in industrial process waters was developed. The sensor is based on the renewable reagent approach and uses the Raipore R1030 membrane as the interface between the sample and the sensor head, which contains 1,5-diphenylcarbazide as spectrophotometric reagent for chromium. Chromium(VI) crosses the membrane and reacts with the reagent inside the sensor head, resulting in changes in the absorption of light. These changes are monitored in situ through a system of optical fibers. The sensor performance was tested by analysing samples from a waste water treatment plant for effluents from electroplating industries.

Anion Exchange Resins↗
PubMed2002

The metal reductase activity of some multiheme cytochromes c: NMR structural characterization of the reduction of chromium(VI) to chromium(III) by cytochrome c(7).

The redox reaction between CrO(4)(2-) and the fully reduced three-heme cytochrome c(7) from Desulfuromonas acetoxidans to give chromium(III) and the fully oxidized protein has been followed by NMR spectroscopy. The hyperfine coupling between the oxidized protein protons and chromium(III), which remains bound to the protein, gives rise to line-broadening effects on the NMR resonances that can be transformed into proton-metal distance restraints. Structure calculations based on these unconventional constraints allowed us to demonstrate that chromium(III) binds at a unique site and to locate it on the protein surface. The metal ion is located 7.9 +/- 0.4 A from the iron of heme IV, 16.3 +/- 0.7 A from the iron of heme III, and 22.5 +/- 0.5 A from the iron of heme I. Shift changes caused by the presence of unreactive MoO(4)(2-), a CrO(4)(2-) analogue, indicate the involvement of the same protein area in the anion binding. The titration of the oxidation of cytochrome c(7) shows a detailed mechanism of action. The presence of a specific binding site supports the hypothesis of the biological role of this cytochrome as a metal reductase.

Binding Sites↗
PubMed1981

Interferences in the spectrophotometric S-diphenylcarbazide determination of environmental hexavalent chromium in a chromium and zinc plating plant.

A study on the determination of environmental hexavalent chromium [Cr(VI)] was carried out in a chromium and zinc plating plant. The atmospheric particulate was collected both on glass wool filters and with an electrostatic sampler; Cr(VI) was determined by the S-diphenylcarbazide method. The filtered and electrostatically collected Cr(VI) was extracted with both 1.4% sulfuric acid and 7% sodium carbonate. Strong interference was observed when extraction was carried out with the acid medium. Alkaline extraction permits 95 +/- 6 (+/- SD)% recovery of the total chromium and has been shown to be suitable in releasing Cr(VI). The analyses of the alkaline samples were carried out with the standard addition method to compensate for a depressive interference of 26 +/- 8 (+/- SD)%. The absorbance decrease of the Cr-S-diphenylcarbazide complex is a time function, and it should be measured within a few minutes of the reagent addition.

Air Pollutants↗
PubMed1991

[Exposure to chromium compounds during processing of chromium iron ore].

The work verifies data gathered by Occupational Hygiene departments of Sanitary-Epidemiological Stations about workers exposure to chromium compounds in the processing of chrome iron ore. Research showed that 7 plants were involved in the processing of chrome iron ore and that the number of workers directly employed in the process amounted to 215-230. About 150 workers were exposed to high concentrations of chromium compounds which exceeded hygienic standards. All of them were employed only in metallurgical plants. The remaining 80-100 workers subjected to the study exposed to relatively low chromium concentrations were employed in chemical plants and refractory materials plants.

Air Pollutants, Occupational↗
PubMed1985

The formation of glutathione-chromium complexes and their possible role in chromium disposition.

The reduction of Cr(VI) to Cr(III) by glutathione (GSH) in vitro resulted in the formation of two different GSH-chromium complexes with an approximate molecular-weight of 10,000 and 5000, respectively. Both complexes exhibited strong fluorescence. The molar ratio between oxidized glutathione (GSSG) and chromium was calculated by determining the chromium content of the two isolated complex species by flameless Atomic Absorption Spectrometry (AAS).

Chromates↗
PubMed2000

Gas-phase reactions of chromium and chromium fluoride cations CrFn+ (n = 0-4) with phosphane.

The reactions of chromium and chromium fluoride monocations CrFn+ (n = 0-4) with phosphane are investigated by Fourier-transform ion cyclotron resonance mass spectrometry. Besides condensing slowly with phosphane, Cr+ is unreactive. The ionic products of the chromium fluoride cations are as follows: (i) CrF+ yields CrPH2+ and subsequently CrPH3+; (ii) from CrF2+, the ions PH3+, Cr+, and CrF2H+ are generated; and (iii) both CrF3+ and CrF4+ yield PH3+. The structure and formation of [Cr,P,H3]+ are investigated by collision-induced dissociation and isotopic labeling experiments. For the neutral species [P,H3,F2] formed by reaction of CrF2+ with phosphane, the structures are interrogated by quantum-mechanical calculations at the MP2/6-31++G** level of theory.

Journal Article↗
PubMed1999

[Low-molecular-weight chromium-binding substances in hepatic and nephric tissues of chromium-exposed rats].

Male Wistar rats were injected intraperitoneally with potassium dichromate(2.55 mg Cr6+ per kg body weight) for 7 days, and were observed continuously for 7 days after stopping Cr injection. The results were that concentrations of chromium-binding substances (HMW-Cr, LMW-Cr, and MMW-Cr) increased significantly with the extension of Cr injection time; MMW-Cr was not found in the control group. MMW-Cr may be a valuable indicator in diagnosing chromium toxication. It was efficient to use Sephadex G-50 column chromatography and ultra-violet absorption spectrometry-atomic absorption spectrophotometry in isolation, and then it was followed by quantitative analysis of chromium-binding substances.

Animals↗
PubMed1997

Microprobe X-ray absorption spectroscopic determination of the oxidation state of intracellular chromium following exposure of V79 Chinese hamster lung cells to genotoxic chromium complexes.

The oxidation state of intracellular chromium has been determined directly in mammalian lung cells exposed to mutagenic and carcinogenic chromium compounds. Microprobe X-ray absorption spectroscopy (XAS) experiments on single V79 Chinese hamster lung cells showed that Cr(VI) and Cr(V) complexes were reduced completely (>90%) to Cr(III) within 4 h of exposure of the cells. This result provides direct evidence for the hypothesis that these genotoxic oxidants react rapidly with intracellular reductants.

Animals↗
PubMed1999

Chromium-tolerant bacteria isolated from industrial effluents and their use in detoxication of hexavalent chromium.

Three bacterial strains were isolated from effluents of leather (CMBL Cr13, CMBL Cr14) and steel (CMBL Cr15) industries for their possible use in chromium(VI) detoxication of industrial waste. CMBL Cr13 was found to tolerate chromium(VI) up to a concentration of 45 g/L in the medium, while CMBL Cr14 and CMBL Cr15 could tolerate up to 40 g/L. These bacteria were also checked for resistance to other metals. They resisted a lead concentration of 1 g/L and cadmium concentration of 550 mg/L in the medium. They showed optimum growth at pH 7.3-7.5 at a temperature of 35-37 degrees C. CrVI-reducing ability of the three strains ranged from 70 to 80% after 3 d of incubation. The possible use of these bacteria in environmental cleanup is discussed.

Biodegradation, Environmental↗
PubMed1991

In vivo nephrotoxicity induced in mice by chromium(VI). Involvement of glutathione and chromium(V).

The role of glutathione (GSH) and chromium (V) in chromium (VI)-induced nephrotoxicity in mice was investigated at 24 h after K2Cr(VI)2O7 ip injection. Nephrotoxicity was assessed by measurements of relative kidney weight and serum urea nitrogen. Cr(VI) nephrotoxicity was accompanied by decreased renal GSH and glutathione reductase (GSSG-R) levels. Pretreatment with buthionine sulfoximine, an inhibitor of GSH biosynthesis, enhanced Cr(VI)-induced nephrotoxicity, and remarkably diminished kidney GSH and GSSG-R levels. In contrast, pretreatment with glutathione methyl ester, a GSH-supplying agent, prevented Cr(VI) from exerting a harmful effect on mouse kidney and restored kidney GSH level. Administration of a Cr(V) compound, K3Cr(V)O8, induced much higher toxicity in mouse kidney than Cr(VI), but it failed to diminish renal GSH level. Another Cr(V) compound, Cr(V)-GSH complex, and Cr(III) nitrate did not cause a nephrotoxic effect in mice. The mechanism of Cr(VI)-induced nephrotoxicity was explained using GSH and Cr(V).

Animals↗
PubMed1984

Distribution and chromium-binding capacity of a low-molecular-weight, chromium-binding substance in mice.

The distribution of low-molecular-weight, chromium-binding substance (LMWCr) and high-molecular-weight, chromium-binding substance (HMWCr) in the organ cytosol were analyzed by means of Sephadex G-25 gel filtration, after a single i.p. injection of K2Cr2O7 (280 mumol, Cr/Kg) to mice (male dd, 23 +/- 2 g). The amount of Cr in LMWCr per mouse was highest in the liver (83 micrograms), followed by those in the kidney (10 micrograms) and other organs (3-1 micrograms), with lesser amounts of Cr in HMWCr in all the organs. In these organs LMWCr was found to bind 3-28 times the amount of Cr to that in the in vivo binding after the in vitro incubation with K2Cr2O7 at 37 degrees C, showing a high Cr binding capacity of the substance. No inductive formation of LMWCr was observed in the liver even after daily repetitive administration of Cr (150 mumol/Kg, 4 days). Time course studies on the liver and the kidney of mice injected with K2Cr2O7 showed no difference in the accumulation of Cr in LMWCr and in the ratio of Cr in LMWCr to that in HMWCr between the organs at intervals of from 5 min to 24 hr after the injection. The comparative affinity of Cr(III) for LMWCr and for the serum proteins decreases in the order LMWCr, transferrin, albumin. The transfer of Cr from LMWCr to albumin and vice versa was almost negligible. However, significant amounts of the metal transfer was found from LMWCr to transferrin and vice versa, and from albumin to transferrin. These findings suggest that LMWCr is distributed widely in the body and it quickly binds invaded Cr in stable form at an organ site, especially in the liver, with participation of albumin or/then transferrin. This supports the hypothesis that LMWCr plays a large role in Cr detoxification.

Animals↗
PubMed1985

Effects of chromium(VI) and chromium(III) on energy charge and oxygen consumption in rat thymocytes.

The cytotoxic effects of chromium compounds in two oxidation states have been studied in rat thymocytes. endogenous nucleotide levels and oxygen consumption were examined as relevant parameters of the physiological state of the cell. Incubation of rat thymocytes with Cr(VI) produced a marked unbalance of endogenous purine nucleotide pool and a parallel decrease in oxygen consumption. A close correlation between the reduction of oxygen consumption and ATP level in rat thymocytes treated with increasing concentrations of Cr(VI) has been found. In rat thymocytes permeabilized with digitonin and in isolated rat liver mitochondria both Cr(VI) and Cr(III) showed, at different range of concentrations, a marked inhibition of maximal oxygen consumption rate (uncoupled respiration). The effects observed were depending on chromium oxidation state and on different mitochondrial sites of substrate oxidation.

Adenosine Diphosphate↗
PubMed2001

Effect of organic solvents in the on-line thermal lens spectrometric detection of chromium(III) and chromium(VI) after ion chromatographic separation.

The effect of methanol, acetone and acetonitrile on the sensitivity, selectivity and the detection limits (LODs) of the determination of chromium species by ion chromatography was investigated. A collinear dual-beam thermal lens spectrometer was used for the direct detection of chromium complexes [pre-column derivatized Cr(III)-pyridine-2,6-dicarboxylic acid, and post-column derivatized Cr(VI)-1,5-diphenylcarbazide] following the ion chromatographic separation on a Dionex HPIC-CS5A solvent compatible column. Different amounts of organic solvents were added directly to the eluent (up to 30%) and to the post-column reagent (up to 60%) to improve the thermooptical properties of the solvents. Consequently, the sensitivity of the technique was increased by a factor of 2-3 and LODs of 0.1 and 10 microg dm(-3) were achieved for Cr(VI) and Cr(III), respectively, when the eluent reaching the detector contained 30% of acetonitrile. The addition of organic solvents also resulted in significant changes in retention times, which improved the Cr(III)/Cr(VI) separation.

Chromatography, Liquid↗
PubMed2003

Determination of hexavalent chromium by on-line dialysis ion chromatography in a matrix of strong colourants and trivalent chromium.

Hexavalent chromium detection in the presence of a high load of colourants without any false positive and in-procedure oxidation of Cr(III) is an important area of study. Colourants are a class of interfering substances in many spectroscopic analyses and chromatographic separations and detection. A purification method using an on-line dialysis technique for ion chromatography (IC) has been developed to remove water-soluble anionic dyes and particulate colourants and other substances to facilitate Cr(VI) quantification and the method is discussed. The dialysis was optimized with Cr(VI) standard solutions for quantification. The efficacy of the procedure for the removal of anionic dyes and detection of Cr(VI) was checked with a Cr(VI) spiked synthetic preparation containing a water-soluble dye and trivalent chromium. Soluble Cr(VI) extracted with organic dyes from environmental samples was analyzed. The method has a detection limit of 5 microg/l, recovery rate of 100% and analysis time less than 20 min.

Chromatography, Liquid↗
PubMed1992

Differential determination of chromium(VI) and total chromium in natural waters using flow injection on-line separation and preconcentration electrothermal atomic absorption spectrometry.

A rapid, sensitive and selective method for the differential determination of CrIII and CrVI in natural waters is described. Chromium(vi) can be determined directly by flow injection on-line sorbent extraction preconcentration coupled with electrothermal atomic absorption spectrometry using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of CrIII to CrVI by potassium peroxydisulfate. Chromium(III) can be calculated by difference. The optimum conditions for sorbent extraction of CrVI and oxidation of CrIII to CrVI are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 microliters samples was achieved after preconcentration for 60 s, giving detection limits of 16 ng l-1 for CrVI and 18 ng l-1 for total Cr (based on 3 sigma). Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100-200 ng l-1. The selectivity of the determination of CrVI was evaluated by analysing spiked reference materials in the presence of CrIII, resulting in quantitative recovery of CrVI.

Chromium↗
PubMed1997

Lack of toxicity of chromium chloride and chromium picolinate in rats.

OBJECTIVE: To evaluate the safety of chromium (Cr) as a nutrient supplement. Several recent studies have reported beneficial effects of supplemental Cr at levels higher than the upper limit of the suggested intake for Cr. Trivalent Cr is considered relatively nontoxic but some recent unconfirmed studies have questioned its toxicity. We evaluated the toxicity of Cr chloride and a more bioavailable form of trivalent Cr, Cr tripicolinate. METHODS: Harlan Sprague Dawley rats (4 weeks of age) were fed a stock diet to which was added 0, 5, 25, 50 or 100 mg of Cr per kg of diet as chloride or picolinate. Fasting blood samples were taken at 11 and 17 weeks and animals sacrificed at 24 weeks of age. Lack of toxicity was demonstrated by blood and histological measurements. Chromium incorporation into tissues was determined by graphite furnace atomic absorption. RESULTS: There were no statistically significant differences in body weight, organ weights or blood variables among all the groups tested at 11, 17 and 24 weeks. Blood variables measured were glucose, cholesterol, triglycerides, blood urea nitrogen, lactic acid dehydrogenase, transaminases, total protein and creatinine. Histological evaluation of the liver and kidney of control and animals fed 100 mg/kg Cr as Cr chloride or picolinate also did not show any detectable differences. Liver and kidney Cr concentrations increased linearly for both the Cr chloride and picolinate fed animals. CONCLUSIONS: These data demonstrate a lack of toxicity of trivalent Cr, at levels that are on a per kg basis, several thousand times the upper limit of the estimated safe and adequate daily dietary intake for humans. Animals consuming the picolinate supplemented diets had several-fold higher Cr concentrations in both the liver and kidney than those fed Cr chloride.

Animals↗
PubMed1991

Role of solubilized chromium in the induction of morphological transformation of Syrian hamster embryo (SHE) cells by particulate chromium(VI) compounds.

Chromium(VI) compounds--Ca, Sr, Zn and Pb chromates--were studied for cytotoxicity and morphological transformation in Syrian hamster embryo (SHE) cells in relation to their solubilization in cell culture conditions and intracellular Cr concentration. Ca, Sr and Zn chromates were completely solubilized after 1 day of incubation in cell cultures; for Pb chromate, 20-36% Cr was solubilized only after 7 days. In two parallel transformation assays, the SHE cells were treated with suspensions or with corresponding supernatants (containing only solubilized Cr) of these compounds. A statistically significant relationship was observed between the Cr treatment concentration and the amount of Cr per cell, irrespective of the compound (except suspensions of Pb chromate). The cytotoxicity was due to extracellular solubilized chromium because treatments with either supernatants or suspensions of Ca, Sr and Zn chromates gave the same LC50 of 0.31 +/- 0.01 microgram Cr/ml. A clear dose-response relationship was observed for the induction of morphological transformation for each compound, either previously solubilized or in suspension. The expression of the transformation frequencies as a function of the Cr concentration/cell revealed that (i) the transformation frequency is dependent on the Cr concentration/cell irrespective of the Cr compound Ca, Sr or Zn chromate, (ii) the transformation frequency induced by solubilized Pb chromate is higher than that induced by the other compounds at the same concentration of Cr/cell. A double treatment with solutions of Cr and Pb at corresponding concentrations induced the same transformation frequency as the solubilized Pb chromate. The results show that the solubilization of particulate Cr(VI) compounds is a critical step for their cytotoxic and transforming activities; the intracellular soluble Cr is the sole causative agent of the transforming activity of Ca, Sr and Zn chromates, while Pb appears to act synergistically with Cr in inducing the transformation by Pb chromate.

Animals↗
PubMed1992

Ascorbate is the principal reductant of chromium(VI) in rat lung ultrafiltrates and cytosols, and mediates chromium-DNA binding in vitro.

Chromium(VI) reductase activity was measured in ultrafiltrates of rat lung after various pretreatments in vitro at 37 degrees C and pH 7.0. Pretreatment of ultrafiltrates with L-ascorbate oxidase (EC 1.10.3.3), which specifically eliminated ascorbate, blocked approximately 95% of chromium(VI) reductase activity in ultrafiltrates. Preincubation of ultrafiltrates with heat-denatured ascorbate oxidase or the sulfhydryl-blocking agent N-ethylmaleimide (NEM) had no significant effect on Cr(VI) reductase activity. In rat lung cytosols, L-ascorbate oxidase blocked approximately 95% and NEM blocked approximately 15% of Cr(VI) reductase activity. The extent of inhibition of Cr(VI) reductase activity in cytosols by L-ascorbate oxidase was significantly decreased to approximately 75% after addition of 1.0 mM NADPH. When Cr(VI) was incubated with salmon sperm nuclei suspended in rat lung cytosol for 15 min, Cr became bound to nuclear DNA. This Cr-DNA binding was completely inhibited by preincubation of rat lung cytosols with L-ascorbate oxidase and inhibited approximately 60% by preincubation with NEM. Taken together these data suggest that ascorbate and/or ascorbate-dependent factors are the principal reductants of Cr(VI) in both ultrafiltrates and cytosols prepared from rat lung and ascorbate-dependent metabolism of Cr(VI) results in Cr binding to nuclear DNA in vitro. Although sulfhydryl-containing factors and NADPH-dependent factors only make a minor contribution to Cr(VI) reduction in rat lung cytosols, sulfhydryls may be significantly involved in the binding of Cr to nuclear DNA.

Animals↗