Chromium In Natural Water Samples Research Articles

Carrier mediated of toxic elements, Part (III) Permeability of Chromium using SLM containing TPPS/xylene and application of chromium in water samples

Extractive removal of chromium Cr (III) from chloride solutions was carried out using TPPS/xylene. The efficiency of this extractant was studied under various experimental conditions, such as concentration of the aqueous phase, concentration of TPPS and Cr (III) present in the initial aqueous feed. The DTPA as stripping phase, temperature and time of extraction was studied. The percentage of Cr (III) extraction decreases with the increase of temperature at varying concentration of TPPS. The interference of the Cr (VI), Cr (III) and chloride were examined at the optimized conditions. Under the optimum experimental conditions 98.6–99.9% of Cr (III) was extracted in 30–50 min at O/A of 1 with the initial feed concentration of 0.5 g/L of Cr (VI). The extracted Cr (III) was quantitatively stripped with 0.02M DTPA. The repeated transport experiments of SLM was shown and to reused in succeeding extraction of chromium (III). Finally a few experiments were performed with the water samples effluent from River Sea and lake. The repeated transport experiment of SLM was shown and the stability of SLM was described using the Danesi’s thermodynamic model. The long-term integrity of SLM was found. Total chromium was determined after the reduction of Cr (VI) to Cr (III) by using ascorbic acid as reducing reagent. The proposed optimization has been applied to the speciation of chromium in natural water samples with satisfactory results.

Neodymium(III) Hydroxide Coprecipitation-FAAS System for the Speciation of Chromium in Natural Waters

A new coprecipitation procedure is presented for the speciation of Cr(III) and Cr(VI) on neodymium(III) hydroxide precipitate. Chromium determination was performed by flame atomic absorption spectrometry. Total chromium was determined by application of the same procedure after reducing Cr(VI) to Cr(III). The concentration of Cr(VI) was calculated by the concentration difference between total Cr and Cr(III). The optimal parameters that affected the quantitative recoveries of Cr(III) were investigated. The influences of co-existing ions were controlled. The detection limit and preconcentration factor for Cr(III) were 2.1 mu g/L and 100, respectively. The method was applied to the speciation and determination of chromium in natural water samples.

Speciation, adsorption and determination of chromium(III) and chromium(VI) on a mesoporous surface imprinted polymer adsorbent by combining inductively coupled plasma atomic emission spectrometry and UV spectrophotometry

In the present study, a Cr(III)-imprinted polymer (Cr(III)-IIP) was prepared by an easy one-step sol-gel reaction with a surface imprinting technique on the support of silica mesoporous material. A new SPE method for the speciation, separation, preconcentration, and determination of Cr(III) and Cr(VI) by inductively coupled plasma atomic emission spectrometry and UV on the mesoporous-imprinted polymer adsorbent was developed. The structure of the imprinted polymer was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The adsorption kinetics, thermodynamics behavior, and recognition ability toward Cr(III) on Cr(III)-IIP and nonimprinted polymer were compared. The results showed that Cr(III)-IIP had higher selectivity and nearly a two times larger Langmuir adsorption capacity (38.50 mg/g) than that of NIP. The proposed method has been successfully applied in the determination and speciation of chromium in natural water samples with satisfactory results.

Room temperature ionic liquids enhanced the speciation of Cr(VI) and Cr(III) by hollow fiber liquid phase microextraction combined with flame atomic absorption spectrometry

A new method for the speciation of Cr(VI) and Cr(III) based on enhancement effect of room temperature ionic liquids (RTILs) for hollow fiber liquid phase microextraction (HF-LPME) combined with flame atomic absorption spectrometry (FAAS) was developed. Room temperature ionic liquids (RTILs) and diethyldithiocarbamate (DDTC) were used enhancement reagents and chelating reagent, respectively. The addition of room temperature ionic liquids led to 3.5 times improvement in the determination of Cr(VI). In this method, Cr(VI) reacts with DDTC yielding a hydrophobic complex, which is subsequently extracted into the lumen of hollow fiber, whereas Cr(III) is remained in aqueous solutions. The extraction organic phase was injected into FAAS for the determination of Cr(VI). Total Cr concentration was determined after oxidizing Cr(III) to Cr(VI) in the presence of KMnO4 and using the extraction procedure mentioned above. Cr(III) was calculated by subtracting of Cr(VI) from the total Cr. Under optimized conditions, a detection limit of 0.7ngmL−1 and an enrichment factor of 175 were achieved. The relative standard deviation (RSD) was 4.9% for Cr(VI) (40ngmL−1, n=5). The proposed method was successfully applied to the speciation of chromium in natural water samples with satisfactory results.

Speciation analysis of chromium in natural water samples by electrothermal atomic absorbance spectrometry after separation/preconcentration with nanometer zirconium phosphate

A sensitive and simple method for the electrothermal atomic absorption spectrometry (ETAAS) determination of Cr(III) after separation/preconcentration on a micro-column packed with nanometer sized zirconium phosphate has been developed. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by 10% (m/v) of aqueous ascorbic acid. The limit of detection for Cr(III) was 1.5 ng/L with an enrichment factor of 300. The static adsorption capacity of the sorbent for Cr(III) was 9.34 mg/g. The relative standard deviation was 3.2% (n = 7, c = 10 ng/mL). The method was applied successfully to the determination of Cr(III) and Cr(VI) in natural water samples.

Speciation of Chromium in Water Samples with Homogeneous Liquid-Liquid Extraction and Determination by Flame Atomic Absorption Spectrometry

‡§ A novel method was developed for the speciation of chromium in natural water samples based on homogeneous liquid-liquid extraction and determination by flame atomic absorption spectrometry (FAAS). In this method, Cr(III) reacts with a new Schiff's base ligand to form the hydrophobic complex, which is subsequently entrapped in the sediment phase, whereas Cr(VI) remained in aqueous phase. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of sodium sulfite to the sample solution. Thus, separation of Cr(III) and Cr(VI) could be realized. Homogeneous liquid-liquid extraction based on the pH-independent phase-separation process was investigated using a ternary solvent system (water-tetrabutylammonium ion (TBA + )-chloroform) for the preconcentration of chromium. The phase separation phenomenon occurred by an ion-pair formation of TBA and perchlorate ion. Then sedimented phase was separated using a 100 µL micro-syringe and diluted to 1.0 mL with ethanol. The sample was introduced into the flame by conventional aspiration. After the optimization of complexation and extraction conditions such as pH = 9.5, [ligand] = 1.0 × 10 ‒4 M, [TBA + ] = 2.0 × 10 ‒2 M, [CHCl3] = 100.0 µL and [ClO4 ‒ ] = 2.0 × 10 ‒2 M, a preconcentration factor (Va/Vs) of 100 was obtained for only 10 mL of the sample. The relative standard deviation was 2.8% (n = 10). The limit of detection was sufficiently low and lie at ppb level. The proposed method was applied for the extraction and determination of chromium in natural water samples with satisfactory results.

Speciation Analysis of Chromium by Adsorptive Stripping Voltammetry in Tap and River Water Samples

AbstractAn adsorptive stripping voltammetric method for speciation analysis of chromium in natural water samples has been developed. Ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) were used as complexing agents for Cr(III) present in the sample and formed as products of Cr(VI) reduction, respectively. Under optimum experimental conditions linear relations in the range from 1×10−6 to 3×10−5 mol L−1 without accumulation and from 1×10−9 to 1×10−7 at 30 s accumulation time were obtained for Cr(III) and Cr(VI), respectively. For samples in which Cr(III) concentration is higher than 1×10−6 mol L−1 the Cr(III) and Cr(VI) were determined simultaneously in one voltammetric cell. For samples in which Cr(III) concentration is below 1×10−6 mol L−1 only Cr(VI) was selectively determined in the presence of Cr(III), which did not influence the Cr(VI) signal. The determination of Cr(III) and Cr(VI) was successful with the application of the proposed procedure in the presence of common foreign ions. The presented method was applied for the speciation of chromium in spiked tap and river water samples with satisfactory results.

Thulium hydroxide: A new coprecipitant for speciation of chromium in natural water samples

A coprecipitation procedure has been established for chromium speciation in natural water samples. The procedure is based on the coprecipitation of Cr(III) on thulium hydroxide precipitate. After reduction of Cr(VI) to Cr(III) by using potassium iodide, the presented method was applied to the determination of the total chromium. The level of Cr(VI) is calculated by difference of total chromium and Cr(III) levels. The procedure was optimized for some analytical parameters including pH, sample volume, matrix effects, etc. The detection limits based on 3 σ criterion were 0.87 μg L −1 for Cr(III) and 1.18 μg L −1 for Cr(VI). The procedure presented was validated by the analysis of BCR-144R Sewage Sludge (domestic origin). The presented method was applied for the speciation of chromium in environmental sample with satisfactory results (recoveries > 95%, R.S.D.s < 10%).

Determination of chromium(III) and total chromium in natural waters using a surface ion-imprinted silica gel as selective adsorbent

A sensitive and selective method has been developed to determine Cr(III) and total Cr in natural water samples by ICP-AES with a Cr(III)-imprinted aminopropyl-functionalised silica gel adsorbent. The Cr(III)-imprinted and non-imprinted adsorbent were prepared by an easy one-step reaction with a surface imprinting technique. Their maximum static adsorption capacities for Cr(III) were 11.12 mg g−1 and 3.81 mg g−1, respectively. The relative selectivity factors (α r) for Cr(III)/Co(II), Cr(III)/Au(III), Cr(III)/Ni(II), Cr(III)/Cu(II), Cr(III)/Zn(II), and Cr(III)/Cr(VI), were 377, 21.4, 15.4, 27.7, 26.4, and 31.9, respectively. Under the optimal conditions, Cr(III) can be absorbed quantitatively, but Cr(VI) was not retained. Total chromium was obtained after reducing Cr(VI) to Cr(III) with hydroxyammonium chloride. The detection limit (3σ) for Cr(III) was 0.11 ng mL−1. The relative standard deviation was 1.2%. The proposed method has been validated by analysing two certified reference materials and successfully applied to the determination and speciation of chromium in natural water samples with satisfactory results.

Determination of Cr(III) and total chromium in water samples by cloud point extraction and flame atomic absorption spectrometry

A sensitive and selective method has been developed for the speciation of chromium in water samples based on cloud point extraction (CPE) separation and preconcentration and determination by flame atomic absorption spectrometry. In the CPE method, Cr(III) reacts with acetylacetone yielding a hydrophobic complex, which is entrapped in the Triton X-100 surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. Under the optimal conditions, the detection limit of this method for Cr(III) was 0.32 ng mL−1 with an enrichment factor of 35, and the relative standard deviation was 3.4% (c = 100 ng mL−1, n = 7). The method has been applied to the speciation of chromium in natural water samples with satisfactory results.

Speciation of chromium in water samples with cloud point extraction separation and preconcentration and determination by graphite furnace atomic absorption spectrometry

A novel method has been developed for the speciation of chromium in natural water samples based on cloud point extraction (CPE) separation and preconcentration, and determination by graphite furnace atomic absorption spectrometry (GFAAS). In this method, Cr(III) reacts with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) yielding a hydrophobic complex, which then is entrapped in the surfactant-rich phase, whereas Cr(VI) remained in aqueous phase. Thus, separation of Cr(III) and Cr(VI) could be realized. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by using ascorbic acid as reducing reagent. PMBP was used not only as chelating reagent in CPE procedure, but also as chemical modifier in GFAAS determination of chromium. The detection limit for Cr(III) was 21 ng L −1 with an enrichment factor of 42, and the relative standard deviation was 3.5% ( n = 7, c = 10 ng mL −1). The proposed method has been applied to the speciation of chromium in natural water samples with satisfactory results.

Chromium speciation by solid phase extraction on Dowex M 4195 chelating resin and determination by atomic absorption spectrometry

A solid phase extraction procedure has been established for chromium speciation in natural water samples prior to determination by atomic absorption spectrometry. The procedure is based on the solid phase extraction of the Cr(VI)- Dowex M 4195 chelating resin. After oxidation of Cr(III) to Cr(VI) by using H 2O 2, the presented method was applied to the determination of the total chromium. The level of Cr(III) is calculated by difference of total chromium and Cr(VI) levels. The procedure was optimized for some analytical parameters including pH, eluent type, flow rates of sample and eluent, matrix effects, etc. The presented method was applied for the speciation of chromium in natural water samples with satisfactory results (recoveries >95%, RSDs <10%). In the determinations of chromium species, flame atomic absorption spectrometer was used. The results were checked by using NIST SRM 2711 Montana soil and GBW 07603 Bush branched and leaves.

Speciation analysis of chromium in natural water samples by electrothermal atomic absorbance spectrometry after separation/preconcentration with nanometer-sized zirconium oxide immobilized on silica gel

Silica gel was prepared by the sol–gel method, modified with nanometer-sized zirconium oxide, and this material was characterized by X-ray diffraction. A micro-column packed with silica gel modified with nanometer zirconium oxide as sorbent has been developed for the quantitative separation and preconcentration of trace amounts of chromium(III) prior to their determination by electrothermal atomic absorption spectrometry. Total chromium was determined after the reduction of chromium(VI) to chromium(III) by 10% (m/v) of aqueous ascorbic acid as reducing reagent. The adsorption capacity for chromium(III) was found to be 2.36 mg g−1. The detection limit for chromium(III) was 15 ng L−1 with an enrichment factor of 100. The relative standard deviation was 3.2% (n = 7, c = 2.0 ng mL−1).

Speciation of Cr(III) and Cr(VI) by nanometer titanium dioxide micro-column and inductively coupled plasma atomic emission spectrometry

A sensitive and selective method has been developed for the speciation of Cr(III) and Cr(VI) in natural water using a nanometer titanium dioxide micro-column (20 mm×3.0 mm i.d.) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Under the optimized conditions (pH 6.0, flow rate 1.0 ml min −1), Cr(III) was retained on the column, then eluted with 2.0 mol l −1 HCl and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid as reducing reagent. The adsorption capacity of nanometer TiO 2 for Cr(III) was found to be 7.6 mg g −1. The detection limit for Cr(III) was 0.32 μg l −1 and the relative standard deviation (R.S.D.) was 2.4% ( n=11, C=100 μg l −1) with an enrichment factor of 50. The proposed method has been applied to the determination and speciation of chromium in natural water samples with satisfactory results.

ON-LINE SOLID PHASE EXTRACTION SYSTEM FOR CHROMIUM DETERMINATION IN WATER SAMPLES BY FLOW INJECTION-FLAME ATOMIC ABSORPTION SPECTROMETRY

ABSTRACT An on-line solid phase extraction system has been established for flow injection flame atomic absorption spectrometric determination of chromium on Chromotrope 2R coated Amberlite XAD-1180 (2R-1180) resin. Some parameters such as pH, flow rates of sample and elution solution, matrix effects on the quantitative recoveries of chromium from the resin were examined. The detection limit (3σ) was 2.59 µg/L for preconcentration at 6.5 mL/min. The method was applied for the determination of traces chromium in natural water samples with satisfactory results (relative standard deviations below 5%, recoveries >95%).

Synthesis and characterization of a new resin functionalized with 2-naphthol-3,6-disulfonic acid and its application for the speciation of chromium in natural water

A polystyrene divinyl benzene (8%) copolymer has been functionalized by coupling it through NN group with 2-naphthol-3,6-disulfonic acid (NDSA). The resulting resin has been characterized by elemental analysis, thermogravimetric analysis and infrared spectra. The hydrogen ion, water regain and metal ion capacities of the resin have been determined. Two forms of chromium show different exchange capacities at different pH values, viz. Cr(III) selectively retained at pH 6.5 whereas Cr(VI) retained at pH 1.5. Hence complete separation of the two forms of chromium is possible. The kinetic studies show that the exchange of Cr(III) and Cr(VI) follows second-order kinetics. The metal ion concentration was measured by flame atomic absorption spectrometry. The method has been successfully applied for the speciation of chromium in natural water samples.