Chromium In Samples Research Articles

Determination of soluble hexavalent chromium in samples of Portland cement from Brazilian cement manufacturers

Urbanization growing is nowadays highlighted in the big cities. Therefore, it is necessary to increase the production of cement, which is used in several areas of civil construction, to supplement the growing demand. Thus, the objective of this study was to determine the content of hexavalent soluble chromium in Portland cement samples from different cement industries in São Paulo state, Brazil, since this chemical species can cause adverse health effects as well as being a potential human carcinogenic for those who manipulate it. In Brazil, the emission of Cr6+ in the cement has no restrictions, since there is no current Brazilian law that determines the maximum concentration of it, whereas, in Europe, the current law 2003/53/EC establishes a maximum of 2 mg.kg-1. So, the Cr6+ content for different cement samples was determined by spectrophotometry based on the European standard EN196-10/2006. It was found by the analysis that among all types of cement produced in São Paulo, the only one that did not exceed the standard limit was the CP III, probably because this kind of cement has a high concentration of additions in its composition, responsible for diluting thereby chromium content. The other types of cement exceeded the established limit. It was concluded that Brazil urgently needs a law to regulate the hexavalent soluble chromium emission present in Portland cement to minimize the environmental and health effects that the cement out of specification may cause.

Chromium in Postmortem Material

Recently, considerable attention has been paid to the negative effects caused by the presence and constant increase in concentration of heavy metals in the environment, as well as to the determination of their content in human biological samples. In this paper, the concentration of chromium in samples of blood and internal organs collected at autopsy from 21 female and 39 male non-occupationally exposed subjects is presented. Elemental analysis was carried out by an electrothermal atomic absorption spectrometer after microwave-assisted acid digestion. Reference ranges of chromium in the blood, brain, stomach, liver, kidneys, lungs, and heart (wet weight) in the population of Southern Poland were found to be 0.11–16.4 ng/mL, 4.7–136 ng/g, 6.1–76.4 ng/g, 11–506 ng/g, 2.9–298 ng/g, 13–798 ng/g, and 3.6–320 ng/g, respectively.

Determinação de Cd, Cr e Pb no leite e na alimentação bovina do Brasil

The contamination of milk is one of the major health concerns because it is largely consumed by population, and the huge extension of the country limits the adequate inspection of this product. Although scientific studies have indicated the occurrence of milk contamination with toxic trace elements, no government policy for the detection and prevention of these components has been available. This study aimed at investigating the occurrence of lead, cadmium and chromium in samples of raw milk and processed milk in an attempt to identify the possible sources of contamination. Both the in natura raw milk and the processed milk evidenced the contamination with these toxic trace elements, and usually at levels above those permitted by Brazilian legislation. The most probable contamination source was the mineral salt employed for feeding cattle.

Anomalous content of chromium in a Cretaceous sandstone aquifer of the Bauru Basin, state of São Paulo, Brazil

Anomalous and natural concentrations of Cr6+, occasionally exceeding the permitted limit for human consumption (0.05 mg/L), have been detected in groundwater in the northwestern region of the state of São Paulo. As part of a water-rock interaction investigation, this article describes the chemical and mineralogical characterization of rock samples taken from boreholes in the municipality of Urânia, with the objective of identifying Cr-bearing minerals and determining how chromium is associated with these minerals. Rock sample analysis were performed using X-ray Fluorescence, X-ray Diffraction, Scanning Electron Microscopy, electron microprobe and sequential extraction techniques. Chemical analyses indicated that the quartzose sandstones show a geochemical anomaly of chromium, with an average content of 221 ppm, which is higher than the reported chromium content of generic sandstones (35 ppm). Diopside was identified as the primary Cr-bearing mineral potentially subject to weathering processes, with a chromium content of up to 1.2% as Cr2O3. Many of the diopside grains showed dissolution features, confirming the occurrence of weathering. Sequential extraction experiments indicated that 99.3% of the chromium in samples is tightly bonded to minerals, whereas 0.24% is weakly bonded via adsorption. Assuming hypothetically that all adsorbed chromium is released via desorption, the theoretical Cr concentration in water would be one order of magnitude higher than the concentrations of Cr6+ detected in groundwater.

LIBS analysis of chromium in samples of dyed wool fabric

A method for the analysis of chromium in wool fabric samples was developed. It is fast and cheap with no sample preparation. This method involved the use of double pulse Laser Induced Breakdown Spectrometry (LIBS) for the wool fabric samples dyed by two types of metal complex dyes (C.I. Acid Orange 173 and C.I. Acid Black 60). A commercially available LIBS spectrometer was calibrated with the aid of authentic wool fabric samples previously analysed by F-AAS after microwave digestion. Comparable results can be obtained using this unique procedure if the same set of standards is used for XRF and LIBS calibration. Limits of detection for chromium achieved by suggested LIBS methods (from 5 to 10 mg kg−1) are comparable with the WD XRF ones (from 4 to 5 mg kg−1).

Seasonal variation in trace metals concentrations in the Ialomita River, Romania

Sampling streams for metals is an important aspect of water-quality monitoring. Using ICP-AES the concentration of some microelements in the Ialomiţa River (Romania) were determined. In order to grasp the different phases of the river regime, samples were collected from its water-sediment interface at seven locations along the river, during three campaigns: during snow melting periods in the mountain zones (April), the period of reduced flow and high water temperature (August) and the period of high precipitations (November). HNO3 was added to the samples for fixation. Cadmium and copper appear accidentally; lead was detected only in samples collected in the vicinity of roads; the MAC (maximum admitted concentration) for surface waters is exceeded for nickel and chromium in samples collected in April and respectively in April and November; zinc concentrations were usually above the MAC; molybdenum concentration was above the set reference value, especially for samples collected in April and November. Possible explanations are given for the presence of the investigated microelements along the river.

Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis

We report a method for determining total chromium in tanning samples using sequential injection analysis (SIA) with a diode-array spectrophotometric detector. With a suitable analytical sequence CrO4(2-) is converted to Cr2O7(2-) inside the tubes of the SIA system, after total oxidation of chromium(III). A data matrix is obtained and analysed by several chemometric techniques based on multivariate analysis: principal components analysis, simple-to-use interactive self-modelling mixture analysis, and multivariate curve resolution-alternating least-squares. We studied several samples from different stages of a tanning process. Two of these samples were easily oxidized but the others needed more extreme conditions. The analytical sequence prepared, which was based on obtaining a pH gradient and used H2SO4 as reagent, is valid and independent of the level of oxidation needed for the sample. We established a calibration model and evaluated the figures of merit. In some samples we found interferents. With this method the amounts of chromium in each sample were quantified and the results were statistically similar to those obtained by use of the reference method, atomic absorption spectrometry.

XAS study of chromium in thermally cured mixture of clay and Cr-containing plating sludge

Chromium oxide and clay are two important refractory ingredients. This study mixed with clay an industrial hazardous electroplating sludge that contained Cr(OH) 3, followed by thermal curing at 900 or 1100 °C for 4 h. Synchrotron-based X-ray absorption spectroscopy (XAS) was used to investigate the change of electronic property of chromium in samples. XANES spectra show that chromium in the mixture thermally cured at 1100 °C is virtually non-Cr(OH) 3 Cr(III), whilst there is considerable fraction of Cr(VI) in that cured at 900 °C. The ingredients in clay enhanced the chemical reduction of Cr(VI) into Cr(III), as indicated by the relatively smaller pre-edge peak in the mixture XANES when in comparison with the raw sludge. For the raw plating sludge heated at 1100 °C, its pre-edge peak position shifts to lower photon energy by approximately 1.0 eV, as compared with that at 900 °C. This indicates that chromium in the 1100 °C heated sludge might have a lesser oxidation state, probably in a form of Cr(V). The intensity of the white band is greater in the Cr XANES spectra from the sample heated at 1100 °C than that heated at 900 °C.

Determination of chromium(III) and total chromium in water by derivative atomic absorption spectrometry using flow injection on-line preconcentration with a double microcolumn.

A rapid and sensitive method has been proposed for the sequential determination of chromium(III) and total chromium in water samples by flame atomic absorption spectrometry combined with a flow injection on-line preconcentration on a double-microcolumn. The chromium(III) and total chromium in samples were retained on a double-microcolumn with a cation exchange resin, respectively, and eluted directly into a nebulizer by 3 mol L(-1) HNO3. The characteristic concentration (gives a derivative absorbance of 0.0044) and the detection limit (3sigma) for chromium were 0.512 microg L(-1) and 0.647 microg L(-1) for a preconcentration time of 1 min, respectively. This is an improvement of 20 and 14-times than those of conventional FI-FAAS. The proposed method allows the determination of chromium in the range of 0-90 microg L(-1) with a relative standard deviation of 3.63% at the 10 microg L(-1) level. The method has been applied for the analysis of chromium in reference water of National Research Center for Certified Reference Materials (GBW08607) and other water samples with satisfactory results.

Flux of heavy metal accumulation in various organs of the intertidal marine blue crab, Portunus pelagicus (L.) from the Kuwait coast after the Gulf War

The metal levels of arsenic, chromium, copper, lead, magnesium, manganese, selenium, vanadium, and zinc concentrations were determined in various body organs, viz., hepatopancreas, gills, gonad, gastric stomach, and muscle of the blue crab, Portunus pelagicus (Crustacea: Decapoda) to assess the bioaccumulation of metals associated with petroleum input a decade after the 1991 Gulf War oil spillage. Sample solutions prepared were analyzed using an atomic absorption spectrophotometry. High concentrations of Zn and Cu in the muscle and hepatopancreas tissues were a strong indicative of high exposure of P. pelagicus to these metals. However, muscle tissue had been found to accumulate the highest values for all metal speciations analyzed. Copper, zinc, and chromium in samples collected from Station II covering the Kuwait City area were often in excess of those present in Station I and III. Arsenic, lead, magnesium, manganese, selenium, and vanadium were greater in individuals obtained from Station I. A significant correlation was found to exist between Se and V in crab muscle with a surge in Se metal concentration, which was found to be inversely proportional to that of V metal concentration irrespective of the sex of the crab. The difference in patterns of metal occurrence and the significant increase in the Cu and Zn concentrations in various organs of the crab were largely associated with the 1991 Gulf War oil spill. Such results could be used as a baseline for the monitoring of the level of metals in marine organisms of future studies.

Flow analysis of micro amounts of chromium(III) and (VI) in natural water by solid phase spectrophotometry using diphenylcarbazide

Specific determination of chromium(III) and chromium(VI) in natural water samples was performed without mutual separation. The chromium in sample solution was concentrated on cation-exchange resin packed in a flow-through cell as a reaction product of chromium(VI) with diphenylcarbazide. The absorbance increase caused by the accumulation of the complex on cation-exchange resin was continuously measured. By using peroxodisulfate as an oxidizing agent, the chromium(III) in sample solution was completely oxidized to chromium(VI). The chromium(III) concentration was calculated by the difference between the values of the total chromium and chromium(VI). The detection limit for chromium(VI) and total chromium was 70 pg and 120 pg, respectively. This method was applied to the specific determination of chromium in several natural water samples. The results of the total chromium obtained by the proposed method show moderate agreement with that obtained with ICP-MS. Unlike the previous results reported in chromium speciation studies, the predominant chromium species in natural water was chromium(VI).

Rapid soil analyses of overburden material from historic mines with SNMS

Plasma-based Secondary Neutral Mass Spectrometry (SNMS) is designed and usually used for depth-resolved determination of the elements in inhomogeneous samples. This report shows that it is also advantageous for the quantification of the total elemental inventory of granular material. As an example of such an application, the quantitative elemental analysis of soil samples from residues of three historic mines in Baden-Wurttemberg is presented. The results obtained with SNMS, using a high primary energy of Ep = 1340 eV, were compared to the concentrations measured by Atomic Absorption Spectroscopy (AAS) and X-Ray Fluorescence (XRF). A reasonable correspondence was found with a mean deviation between all three methods of about 50%. However, SNMS measurements of standard soils, without any matrix adaptation of the elemental sensitivities, exhibited mean deviations from the certified concentrations of only 20–30 wt% down to concentrations below 10–2 wt%. The advantages of SNMS against AAS and XRF are its simple sample preparation and the rapid detection of all elements in the analyzed material within some 10 min. In each of the three samples chromium, nickel, copper, zink and lead (only sample HS 64) were found in concentrations exceeding the limiting values of the German Sewage Sludge Ordinance (SSO).

Development of a procedure for the determination of chromium in samples of urine and serum by neutron activation analysis

Since the mid-fifties the possibility of a causal relationship between deficient chromium and insulin metabolism and the manifestation of certain varieties of diabetes mellitus has been presumed. The determination of the chromium status under pathophysiological conditions may be helpful for the study of this problem. For these purposes an analytical procedure as reference system was developed which allows the determination of chromium in biological matrices down to the concentration of 0.03 ng/ml. It is based on NAA and is used in the framework of a commonly used procedure based on GF-AAS. For its application blood and urine samples are freeze-dried and irradiated. After wet digestion with HNO3 in a microwave combustion system chromium is separated for measurement from the matrix nuclides with the help of the ion-exchanger Cellex-P. The individual steps of the procedure were evaluated by means of tracer experiments.

Sample Preparation Methods for Analysis of Spent Chrome Ores

Two methods of sample preparation were compared for analysis of total chromium in samples of spent ore. These spent ores result from the production of chromium chemicals. In the standard method used by the U.S. Environmental Protection Agency, the sample is reacted with nitric and hydrochloric acids and hydrogen peroxide to extract the reacted chromium from the solid matrix and to convert the chromium to the soluble hexavalent state. In the proposed alternative method of sample preparation, the sample is reacted with oxidants in an alkaline medium to more completely convert the chromium to the hexavalent state. The oxidized chromium sample is then dissolved in a hydrochloric acid solution for analysis. High and low chromium concentration samples of spent ore were prepared using the EPA and our proposed methods. Solutions were analyzed using two accepted wet chemistry methods. Comparisons were made of the efficiency of the sample preparation methods and a recommendation is made for further work.

Evidence from chromium abundances in mantle rocks for extraction of picrite and komatiite melts

ONE of the more important aspects of understanding the geochemical differentiation of the Earth is an accurate knowledge of the compositions of magmas produced by direct melting of the upper mantle, which are called primary magmas1. It is clear that a variety of primary magma compositions can develop within the mantle, depending on the source composition, the presence of volatiles, the extent of melting and the pressure of melt segregation1–4. Proposed primary magma compositions span a wide composition range, from basalts with ∼8–ll% MgO, through picrites with ∼11–20% MgO, to komatiites with ∼20–28% MgO; there is no agreement as to which is the dominant type of primary magma. We suggest here that the abundances of chromium in samples of the Earth's upper mantle indicate that, of the wide variety of possible primary liquids produced in experimental studies of mantle melting, the dominant type of primary liquid actually extracted from the mantle has been picritic to komatiitic, with ≳;15% MgO.

Application of Atomic Magneto-Optical Rotation Spectroscopy to Direct Determination of Trace Copper, Manganese and Chromium

Atomic magneto-optical rotation spectroscopy (AMORS) based on the Faraday effect was applied to direct determination of trace amounts of copper, manganese and chromium in samples containing complex matrices: The NBS Orchard Leaves, the NBS Bovine Liver, mandarine orange juice and volcanic ashes. Suspensions of powder samples and diluted juice were pipetted into a graphite tube atomizer and atomized directly or after mild charring. One of the AMORS’s inherent advantages is the insensitivity to background scattering caused by non-atomic species which is generated from sample matrix on atomization. This facilitates analyses by direct atomization. Such an advantageous feature of AMORS is exemplified in the practical analyses.

Tablaser: trace (element) analyzer based on laser ablation and selectively excited radiation

Trace element analysis based on laser ablation and selectively excited radiation (TABLASER) is proposed as a new and reliable microultratrace technique for quantitative in situ element analysis. Measurements of trace quantities of chromium in samples of NBS standard reference steel, doped skim milk powder, and doped flour have been undertaken. A linear 45 degrees slope dependence of signal vs concentration that extends beyond 1% in the case of chromium was observed. Although the present sensitivity limit is in the ppm range, improved overlap between the probing dye laser beam and the wave of atomized material combined with a better design of the optical system could reduce the detection limit of the TABLASER to the ppb range. This would correspond to an absolute detection limit of about 10(-16) g. An important feature of this new technique is its relative freedom from chemical matrix effects, which suggests the possibility of a universal calibration curve for all elements irrespective of the substrate matrix in which they are contained. This technique is also adaptable to multielement analysis.

The absolute abundance of the chromium isotopes in some secondary minerals

Isotopic assays have been made on the chromium in samples from fourteen different chrominiferous minerals from different geographic and meteoritic sources. The results of the assays indicate that it is not possible to unequivocally state that variations in isotopic composition have been observed.