Determination Of Total Cr Research Articles

Bottom-up uncertainty evaluation of complex measurements from correlated performance data: Determination of total Cr in yeast by ICP-MS after acid digestion

The objective interpretation of a measurement result requires knowing the associated uncertainty. The cost-effective collection of measurement performance data on the same day produces correlated values that can affect measurement uncertainty evaluation. This work describes a novel methodology for the bottom-up evaluation of measurements based on complex sample pretreatment and the instrumental quantification of the prepared sample applicable to correlated inputs. The numerical Kragten method is used to combine the uncertainty components shared in various analyte recovery determinations. The developed methodology was applied to the determination of total chromium in yeast samples by ICP-MS after microwave-assisted acid digestion. The developed analysis of yeast samples is fit for monitoring the contamination of this product since it is associated with a relative expanded uncertainty, U’, lower than 20%, ranging from 8.4% to 10.0% in determinations of Cr between 0.125 mg/kg and 305.5 mg/kg. Duplicate analyses are adequate for reference materials production (U′ < 7%).

Ion-exchange HPLC-ICP-MS: A new window to chromium speciation in biological tissues

The presented work proposes a novel analytical ICP-MS-based approach for the accurate and precise chromium speciation in biological tissues. The determination of total Cr(VI) and soluble Cr(III) species was carried out by alkaline EDTA extraction followed by their separation using ion-exchange high-performance liquid chromatography inductively coupled plasma mass spectrometry (IE-HPLC-ICP-MS). The developed method was validated according to the procedure given in the United States Food and Drug Administration guideline on the validation of bioanalytical methods. Validation parameters included limit of detection (≤ 0.03 μg g−1), limit of quantification (≤ 0.08 μg g−1), linearity (r ≥ 0.9998), intra-day and inter-day accuracy (86–110%) and precision (≤ 10%), extraction recovery (89–110%), carry-over effect and sensitivity. In addition, special attention was paid to the study of chromium species interconversion and the elimination of spectral interferences. Moreover, the validated ICP-MS method employing microwave acid digestion was used to determine the total Cr content in collected fractions. Finally, the whole ICP-MS-based methodology was applied to the analyses of two certified reference materials of hepatopancreas tissue. Obtained results indicated that the majority of chromium in biological tissues is bound to the solid residue, Cr(VI) was determined in none of the samples investigated. This is the first study focusing on soluble Cr(III), total Cr(VI), and total bound Cr species in biological tissues. It is characterized by efficient sample preparation and fast simultaneous analysis of Cr species with parallel total Cr analysis serving for chromium balance evaluation.

Chromium Leachability from Leather Waste and Eco-toxicity under Environmental Conditions

Chromium (III) is currently used in leather manufacture worldwide and the attention has been centered on the alleged environmental impact of chromium in leather waste. The effects of liquid-solid ratio, pH, contact time, rotational speed and temperature on the leachability of chromium from leather waste and the eco-toxicity were evaluated to investigate the ecological impact under environmental conditions. The characterization of leachate included the determination of total Cr and total organics (TOC), analysis of UV-visible absorption spectra, as well as the toxicity test with Photobacterium phosphoreum. The liquid-solid ratio, extractant pH, contact time and temperature significantly affected the leachability of chromium and toxicity of the leachate, whereas rotational speed slightly affected the leaching behavior when beyond 100 RPM. The toxicity of the leachate was related to both the amount of released substance which was mainly affected by contact time and liquid-solid ratio, and the species which was mainly affected by temperature and extractant pH. Finally, three samples from different tannery corresponding to leather waste were leached and characterized by total Cr, TOC and toxicity test under the environmental conditions of liquid-solid ratio 20:1(mL/g), pH 7.0, contact time 8 hours, rotational speed 100 RPM and temperature 25°C. These results contributed to the risk assessment of stacking field and waste management of chrome-containing leather.

Disposable plastic electrode for electrochemical determination of total chromium and hexavalent chromium

We report a sensitive electrochemical protocol based on an easy-to-produce and disposable plastic electrode for the determination of total chromium (Cr) and Cr(VI). The electrode was fabricated by sputtering a thin layer of gold on a polyethylene terephthalate (PET) substrate. The experimental factors influencing the fabrication and electrochemical analysis as well as potential interferences were investigated. Under optimum conditions, the determination of total Cr was achieved by adsorptive cathodic stripping voltammetry and the linear range was from 5 to 70μgL−1 and from 70 to 300μgL−1 with a limit of detection of 5μgL−1. The analysis of Cr(VI) was performed by amperometry and linearity in the range from 0.5 to 100μgL−1 with a limit of detection of 0.5μgL−1 was obtained. The applicability to spiked river water and textile samples was demonstrated with satisfying results. The proposed method has been proved to provide more convenient sensor fabrication and much higher sensitivity than other reports based on disposable electrodes. We believe it may provide a promising alternative for routine analysis of total Cr and Cr(VI).

Optimization and validation of strategies for quantifying chromium species in soil based on speciated isotope dilution mass spectrometry with mass balance

Strategies were designed to quantify hexavalent (Cr(VI)), soluble trivalent (Cr(III)) and insoluble chromium (Cr) species in soil by integrating existing methods of Cr(VI) and total Cr determination with speciated isotope dilution mass spectrometry (SIDMS, EPA Method 6800). Two different extraction methods that utilize a NaOH–Na2CO3 solution (EPA Method 3060A) and alkaline solution of ethylenediaminetetraacetic acid (EDTA) were used to extract Cr(VI) (along with soluble Cr(III) in the latter case). The extracted Cr was speciated by ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS), and the separated species were quantified using the mathematical relationships in SIDMS with simultaneous correction for their method-induced transformations. The Cr species that fell out as insoluble solid during extraction were determined by isotope dilution mass spectrometry (IDMS) after decomposing the extraction residues in a mixture of mineral acids according to EPA Method 3052. Several certified reference materials and a soil sample were analyzed using the proposed strategies. The measured mass fractions of Cr(VI) and total Cr in the reference materials statistically agreed with the certified values at 95% CL. The insoluble fraction of Cr accounted for 64–107% of the total Cr in the samples. The validity of the strategies was proved using mass balance by comparing the sum of the mass fractions of Cr(VI), soluble Cr(III) and insoluble Cr with the total Cr measured in the corresponding samples; the latter was determined by IDMS after decomposing the soils using EPA Method 3052 with single spiking.

Determination of total Cr in wastewaters of Cr electroplating factories in the I.organize industry region (Kayseri, Turkey) by ICP-AES

The wastewater pollution in industrial areas is one of the most important environmental problems. Heavy metal pollution, especially chromium pollution in the wastewater sources from electroplating, dyeing, and tannery, has affected the life on earth. This pollution can affect on all ecosystems and human health directly or by food chain. Therefore, the determination of total chromium in this study is of great importance. In this study, accurate, rapid, sensitive, selective, simple, and low-cost technique for the direct determination of total Cr in wastewater samples collected from the some Cr electroplating factories in March 2008 by inductively coupled plasma-atomic emission spectrometry has been developed. The analysis of a given sample is completed in about 15 min by this technique applied. As the result of the chromium analysis, the limit of quantification for the total Cr were founded to be over the limit value (0.05 mg L(-1); WHO, EPA, TSE 266, and inland water quality classification) as 1,898.78+/-0.34 mg/L at station 1 and 3,189.02+/-0.56 mg/L at station 2. The found concentration of total Cr has been determined to be IV class quality water according to the inland water classification. In order to validate the applied method, recovery studies were performed.

Speciation of chromium in cow's milk by solid-phase extraction/dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)

Chromium can act either as an essential micronutrient or a chemical carcinogen, depending on its oxidation state. Of the two most stable chromium oxidation states, Cr(VI) is a known carcinogen, while Cr(III) is an essential element. Determination of total Cr cannot therefore be used to evaluate food safety of dairy products, as speciation is required for accurate assessment of potential toxicity. In this study, total Cr was determined by DRC-ICP-MS after mineralisation of freeze-dried milk samples. Chromabond NH2ion-exchange columns were used to separate Cr(VI) from Cr(III). During the separation process, Cr(VI) was selectively adsorbed onto the Chromabond NH2 column. The retained Cr(VI) was subsequently eluted with two column volumes of 2 M HNO3 and diluted to a final volume of 10 mL. After separation, the Cr(VI) was quantified by DRC-ICP-MS, using O2 as the reactive gas, to alleviate polyatomic ion interference. An O2 gas flow rate of 0.85 ml/min and a high-pass rejection parameter q (Rpq) = 0.5, provided the best compromise signal-to-noise ratio. The method was validated through determining the recovery in milk samples spiked with Cr(VI). The recoveries were quantitative and ranged from 96.4 to 99.2%. A whole milk powder reference material (NIST SRM 8435) was used to evaluate the accuracy of the total Cr quantification method. The observed value showed concordance with the certified value. The limits of detection (LOD) were 0.091 and 0.085 µg/L for total Cr and Cr(VI), respectively. These findings are important for the determination of maximum residue levels (MRLs) of Cr(VI) in dairy products.

Chemiluminescence determination of chromium(III) and total chromium in water samples using the periodate-lucigenin reaction

A new chemiluminescence (CL) method combined with flow injection technique is described for the determination of Cr(III) and total Cr. It is found that a strong CL signal is generated from the reaction of Cr(III), lucigenin and KIO4 in alkaline condition. The determination of total Cr is performed by pre-reduction of Cr(VI) to Cr(III) by using H2SO3. The CL intensity is linearly related to the concentration of Cr in the range 4.0 × 10−10–1.0 × 10−6 g mL−1. The detection limit (3sb) is 1 × 10−10 g mL−1 Cr and the relative standard deviation is 1.9% (5.0 × 10−8 g mL−1 of Cr(III) solution, n = 11). The method was applied to the determination of Cr(III) and total Cr in water samples and compared satisfactorily with the official method.

Chromium speciation study in polluted waters using catalytic adsorptive stripping voltammetry and tangential flow filtration

The catalytic adsorptive stripping voltammetry (CAdSV) has been applied to physico-chemical chromium speciation study in the upper Dunajec catchment, severely polluted by the tannery wastewater. The method is based on the adsorptive preconcentration of the Cr(III)–diethylenetriammine-N,N,N′,N″,N″-pentaacetic acid (DTPA) complex and the utilization of the catalytic reaction in the presence of nitrate. Under optimized conditions the CAdSV enables the oxidation state speciation study of Cr content by direct determination of Cr(VI) in the presence of the predominant Cr(III) concentration with the detection limit for chromium(VI) of 0.08 nM and the linearity range from 0.1 to 80 nM obtained for 20 s of accumulation, as well as the determination of total Cr after UV oxidation of Cr(III) to Cr(VI). Due to the difference in the chemical properties of different chromium species the CAdSV method makes possible a speciation study of Cr(III) and Cr(VI) oxidation state. The RSD of the determination of Cr(VI) and Cr(III) varies from 0.5 to 5%. It has been proved that in natural water in which strong complexants of Cr(III) such a humid acids are presented, Cr(VI) can be determined accurately in the presence of high excess of Cr(III). Fractionation of selected water samples with tangential flow filtration (TFF, cut-off 10 and/or 1 kDa) provides insight into physical Cr speciation, i.e. partitioning of the Cr(VI) and Cr(III) between the colloidal and the dissolved fractions. It has been shown that the content of the Cr species in the Dunajec river depends on the season, and is significantly higher in autumn and winter during the most intensive tanneries production processes. The concentration of total Cr exceeds occasionally the legally admissible level. A large fraction of total Cr(III) concentration is associated with the colloidal material, while Cr(VI) occurs solely in the truly dissolved form.

Chromium speciation study in polluted waters using catalytic adsorptive stripping voltammetry and tangential flow filtration

The catalytic adsorptive stripping voltammetry (CAdSV) has been applied to physico-chemical chromium speciation study in the upper Dunajec catchment, severely polluted by the tannery wastewater. The method is based on the adsorptive preconcentration of the Cr(III)–diethylenetriammine-N,N,N′,N″,N″-pentaacetic acid (DTPA) complex and the utilization of the catalytic reaction in the presence of nitrate. Under optimized conditions the CAdSV enables the oxidation state speciation study of Cr content by direct determination of Cr(VI) in the presence of the predominant Cr(III) concentration with the detection limit for chromium(VI) of 0.08nM and the linearity range from 0.1 to 80nM obtained for 20s of accumulation, as well as the determination of total Cr after UV oxidation of Cr(III) to Cr(VI). Due to the difference in the chemical properties of different chromium species the CAdSV method makes possible a speciation study of Cr(III) and Cr(VI) oxidation state. The RSD of the determination of Cr(VI) and Cr(III) varies from 0.5 to 5%. It has been proved that in natural water in which strong complexants of Cr(III) such a humid acids are presented, Cr(VI) can be determined accurately in the presence of high excess of Cr(III). Fractionation of selected water samples with tangential flow filtration (TFF, cut-off 10 and/or 1kDa) provides insight into physical Cr speciation, i.e. partitioning of the Cr(VI) and Cr(III) between the colloidal and the dissolved fractions. It has been shown that the content of the Cr species in the Dunajec river depends on the season, and is significantly higher in autumn and winter during the most intensive tanneries production processes. The concentration of total Cr exceeds occasionally the legally admissible level. A large fraction of total Cr(III) concentration is associated with the colloidal material, while Cr(VI) occurs solely in the truly dissolved form.

Determination of Cr(III) and Cr(VI) by solvent extraction-atomic absorption spectrophotometry

Masking a large amount of Cr(III) with EDTA, micro amounts of Cr(VI) were extracted into methyl isobutyl ketone (MIBK) as diethyl dithiocarbamate (DDTC) complex and analyzed by atomic absorption spectrophotometry.(a) Determination of Cr(VI): Take a sample solution {containing less than 50 μg of Cr(VI)} into a 100 ml beaker, add 10.0 ml of 0.2 M EDTA solution and boil for 5 min. After cooling to room temperature, adjust the pH value to 45. Transfer the solution to a 100 ml separatory funnel, add 2.5 ml of 2% DDTC solution and make the total volume of it to 50 ml with distilled water. Add 10.0 ml of MIBK and shake the solution vigorously for 5 min. Wash the stopper of the separatory funnel with samll quantities of water and stand for 10 min. Separate the layers and measure the Cr concentration in the MIBK extract with a Hitachi model 207 atomic absorption spectrophotometer, using air-acetylene flame (analytical line; 3579 A). The extractability of Cr(VI) was 74.8%. The respective presence of less than 5-fold Bi(III), 20-fold Co(II), 10-fold Fe(III) and 5-fold V(V) of Cr(VI) did not interfere. (b) Determination of total Cr: Take a sample solution (containing less than 20 mg of Cr) into a beaker, add 2 ml of (1+4) H2SO4. Add 0.01 N KMnO4 solution dropwise while heating until the solution becomes faintly pink, and boil for 5 min. After cooling, dilute to constant volume with distilled water. Then, take a given volume (containing less than 40 μg of Cr) of the solution, adjust the pH value to 45 Transfer the solution to a 100 ml separatory funnel and determine amounts of Cr as the procedure (a) after addition of 2% DDTC solution. The extractability of Cr(VI) in this case was 98.1%.Amounts of Cr(III) were calculated from difference between those of total Cr and Cr(VI). The relative error was +3%.