Trace Chromium Research Articles

Determination of Trace Chromium (VI) in Tanning Wastewater by Flow Injection Spectrophotometry

In 1.0 mol/L H2SO4 solution, a rapid and simple flow—injection spectrophotometric method has been developed for Cr(Ⅵ) determination, based on the violet—red Cr(Ⅵ)—diphenylcarbazide chelates formed by reactions. The results show, under optimum conditions, the maximum absorption of the complex is at 540 nm and the detection limits of the method is 0.0136mg/L for Cr(Ⅵ) and Beer’s law is obeyed for Cr(Ⅵ) in the range of 0.03—1.60mg/L. The determination frequency is l00 times/h. The relative standard deviation of eleven replicates is less than 4.0%. The method has been applied to the determination of trace Cr(Ⅵ) in tanning wastewater with satisfactory results.

Magnetic immobilization of amine-functionalized magnetite microspheres in a knotted reactor for on-line solid-phase extraction coupled with ICP-MS for speciation analysis of trace chromium

The use of magnetic microspheres and nanoparticles for sample extraction in analytical chemistry has received increasing interest. However, previous magnetic particle-based solid-phase extraction (SPE) is usually performed in a batch mode. In this work, we report magnetic immobilization of amine-functionalized magnetite (Fe3O4) microspheres (AF-MMPs) onto the inner walls of a knotted reactor (KR) for on-line SPE coupled with ICP-MS for speciation analysis of trace chromium. A tubular magnet is sufficient to immobilize AF-MMPs onto the inner walls of a KR without the need for any frits or plugs. Sensitive speciation analysis of trace CrIII and CrVI in water was achieved based on selective on-line SPE of either CrIII and CrVI under controlled pH conditions on an AF-MMPs magnetically immobilized KR integrated into a flow injection system with on-line ICP-MS detection without the need for extra oxidation/reduction. On-line SPE of 2.4 mL aqueous solution gave an enhancement factor of 96 for CrIII and 47 for CrVI, a detection limit of 1.5 ng L−1 for CrIII and 2.1 ng L−1 for CrVI at a sample throughput of 23 h−1. The precision (RSD) for eleven replicate measurements of 100 ng L−1 CrIII and CrVI was 1.9% and 4.5%, respectively. The batch-to-batch reproducibility (RSD) for three parallel prepared AF-MMPs packed KRs for the SPE of CrIII and CrVI at 100 ng L−1 was less than 5.5%. One AF-MMPs packed KRs can be used for at least 75 cycles of preconcentration without significant loss of extraction efficiency. The developed method was successfully applied to the speciation analysis of trace CrIII and CrVI in drinking water samples.

A Simple and Sensitive Method for the Amperometric Detection of Trace Chromium(VI) Based on Prussian Blue Modified Glassy Carbon Electrode

AbstractA simple and sensitive method for the amperometric detection of trace amount of chromium(VI) using a Prussian blue modified glassy carbon electrode (PB/GCE) is described here. The Everitts salt/Prussian blue redox couple of the PB film was found to mediate the Cr(VI) reduction, and the mechanism of electrochemical reaction was investigated. The effects of PB film thickness, applied potential and electrolyte solution on the current response of Cr(VI) reduction were thoroughly studied. Under the optimized conditions, the PB/GCE provided a wide linear range for Cr(VI) analysis from 0.5 to 200 ppb with excellent sensitivity (15±0.2 nA/ppb) and low detection limit (0.15 ppb). In addition, the modified electrode showed excellent stability, reproducibility and good resistance to other metal ions and surfactants. Finally, the proposed method was applied to detect trace Cr(VI) in wastewater with satisfactory results. The great advantages of the method were characterized by the simplicity, ease of preparation, stability, short analysis time and cost‐efficiency.

Characteristics of Voltammetric Determination and Speciation of Chromium – A Review

AbstractThis article reviews the voltammetric methods of chromium determination, including adsorptive and catalytic adsorptive stripping voltammetry at liquid mercury, metallic films, and modified carbon paste electrodes. The principle applications of the catalytic adsorptive stripping voltammetric method of chromium(VI) determination in the presence of DTPA and nitrate, most useful in the analysis of chromium traces and its speciation, is presented in detail. Special emphasis is put on the presentation and characterization of the voltammetric procedures which make it possible to conduction speciation studies of chromium(VI) in the presence of a great excess of chromium(III) and surfactants. This survey is based on 173 articles.

Organically nanoporous silica gel based on carbon paste electrode for potentiometric detection of trace Cr(III)

A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5 wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0 × 10 −8 to 1.0 × 10 −3 M toward Cr(III) with a detection limit of 8.0 × 10 −9 M and a Nernstian slope of 19.8 ± 0.2 mV decade −1. The as-prepared electrode displayed rapid response (∼55 s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5–5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV–vis spectroscopy.

Investigation of polarographic interference between Se(IV) and Cr(VI), its elimination and application to Gerede river water

Trace chromium(VI) determination plays an important role since it is carcinogenic agent and toxic pollutant. For this purpose a direct method is developed using differential pulse polarography, DPP. When selenite was added into solutions of some ions such as copper(II), lead(II), cadmium(II), zinc(II), and chromium(VI) their DP polarographic peak decreased. This kind of interference will cause large errors in the determinations, its elimination is very important. The interference between selenite and Cr(VI) ions could be eliminated in B-R (Britton-Robbinson) buffer at pH 8.5. In this work the effect of components present in buffer has been investigated and it was found that phosphate and borate eliminated the formation of Cr–Se intermetallic compound formation. While it was possible to determine 1 × 10 −5 M Cr(VI) in the presence of 100 times more selenite as (1.0 ± 0.1) × 10 −5 M, in borate medium, it was possible to determine (1.0 ± 0.05) × 10 −5 M in phosphate medium. In the presence of selenite detection limit ( S/ N = 3) was 9.0 × 10 −8 M Cr(VI) by using either phosphate or borate This method was applied to Gerede river water, after oxidation all Cr(III) present into Cr(VI).

Determination of Total Chromium in the Marine Sediment Certified Reference Material by Inductively Coupled Plasma Optical Emission Spectrometry after Pressurized Acid Decomposition

(1) The marine sediment (NMIJ CRM 7302a) was directly decomposed with a mixture of 1 mL of hydrofluoric acid, 1 mL of nitric acid and 8 mL of (1 + 1)sulfuric acid in a Teflon sealed vessel at 230°C for 16 h. The total chromium was determined. (2) An indirect acid method after the decomposition of organic materials by H2SO4-HNO3 was compared to a direct acid decomposition method (1). The analytical results of the total-chromium (t-Cr) by methods (1) and (2) coincided with the certified value of the NMIJ CRM 7302a. The direct method of (1) was recommended for a pre-treatment of a marine sediment sample. On the other hand, an electron probe micro-analyzer (EPMA) was applied to an element analysis of the trace precipitation in a direct acid decomposition process in a Teflon-sealed vessel. The white trace precipitation was a crystal of AlF, and the black trace precipitation was carbon. Trace chromium was not detected by the precipitations. How to obtain accurate data from the pre-treatments was discussed regarding the data of this method and other data : that is EPA 3050B, ISO 11466, EPA 3052B, or NAA found from the Union Internationale des Laboratories Indepentants, Inter-Laboratoriy Practice report. The importance of deciding the assigned value was discussed for a statistical evaluation of the data of participants in a proficiency testing. The certified reference materials (CRM) should be furnished by both the sheet decomposition methods of CRM in addition to methods (sheet) for accurate quantitative analyses of the analytes in the CRM.

A study of nanostructured gold modified glassy carbon electrode for the determination of trace Cr(VI)

A nanostructured gold modified glassy carbon electrode (Aunano/GCE) was employed for the determination of trace chromium(VI). To prepare Aunano/GCE, the GCE was immersed into KAuCl4 solution and electrodeposition was conducted at the potential of −0·4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles were deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analysed to ensure that common interference in the determination of chromium(VI) by square wave voltammetry, do not influence the electrochemical response of the latter element. The results show that this method allows for Cr(VI) determinations with a much lower detection limit (0·01 µg L−1) in the presence of excess of Cr(III) than the commonly used diethylenetriammine pentaacetic acid (DTPA) method. The method was applied to determine levels of chromium(VI) in tap water and sewage water.

Evaluation of chromium contamination in water, sediment and vegetation caused by the tannery of Jijel (Algeria): a case study

In order to evaluate the chromium (Cr) contamination due to the discharge of waste waters from the tannery of Jijel in the Mouttas river (Algeria), samples of water, sediment and vegetation (Agropyrum repens) were collected during a 6 month period in four stations located upstream (control) and downstream of the tannery. The total chromium was measured by atomic absorption spectrophotometry. Metal inputs were clearly related to effluent discharges from the tannery into the river. Although only traces of chromium were found in water samples upstream of the tannery, very high concentrations (up to 860 times higher) were detected downstream. The contamination was not limited to water of Mouttas River because a same difference in chromium concentrations was also found in sediments and plants Agropyrum repens that were sampled upstream and downstream of the tannery. This work showed that the treatment process used in the wastewater treatment plant of the tannery of Jijel is not able to remove the chromium detected in their influents. The occurrence and chromium levels detected in the aquatic environment represent a major problem concerning drinking water resources and environmental protection of water bodies.

Rapid determination of chromium(VI) in electroplating waste water by use of a spectrophotometric flow injection system

A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water. The method is based on the reaction of Cr(VI) with sodium diphenylamine sulfonate (DPH) in acidic medium to form a purple complex ( λ max = 550 nm). Under the optimized conditions, the calibration curve is linear in the range 0.04–3.8 μg m l −1 at a sampling rate of 30 h −1. The detection limit of the method is 0.0217 μg m l −1, and the relative standard deviation is 1.1% for eight determinations of 2 μg ml −1 Cr(VI). The proposed method was applied to the determination of chromium in electroplating waste water with satisfactory results.

Chromium(III)-imprinted silica gel for speciation analysis of chromium in environmental water samples with ICP-MS detection

A new chromium(III)-imprinted 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS)-functionalized silica gel sorbent was synthesized by a surface imprinting technique and was employed as a selective solid-phase extraction material for speciation analysis of chromium in environmental water samples prior to its determination by inductively coupled plasma mass spectrometry (ICP-MS). The prepared Cr(III)-imprinted silica gel shows the selectivity coefficient of more than 700 for Cr(III) in the presence of Mn(II). The static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Cr(III) were 30.5 mg g −1 and 13.4 mg g −1. It was also found that Cr(VI) could be adsorbed at low pH by the prepared imprinted silica gel, and this finding makes it feasible to enrich and determine Cr(VI) at low pH without adding reducing reagents. The imprinted silica gel sorbent offered a fast kinetics for the adsorption and desorption of both chromium species. Under the optimized conditions, the detection limits of 4.43 pg mL −1 and 8.30 pg mL −1 with the relative standard deviations (R.S.D.s) of 4.44% and 4.41% ( C = 0.5 ng mL −1, n = 7) for Cr(III) and Cr(VI) were obtained, respectively. The proposed method was successfully applied to the speciation of trace chromium in environmental water samples. To validate the proposed method, two certified reference materials were analyzed and the determined values were in a good agreement with the certified values. The developed method is rapid, selective, sensitive and applicable for the speciation of trace chromium in environmental water samples.

Determination of trace elements in food samples by ICP-AES after preconcentration with p-toluenesulfonylamide immobilized on silica gel and nanometer SiO2

p-Toluenesulfonylamide was immobilized on silica gel and on nm-sized silicium dioxide (SiO2). Their adsorption efficiency toward metal ions was investigated by the batch equilibrium technique. Although silica gel and nm-SiO2 have the same composition (silicon and oxygen), the difference in their sizes and surface structures results in distinct chemical activity and selectivity. At pH 4, the adsorption capacity of modified silica gel adsorbent was found to be 4.9, 5.0, 33.2, and 12.6 mg g−1 for Cr(III), Cu(II), Pb(II) and Zn(II), respectively. However, the adsorption capacity of nm-SiO2 adsorbent toward Cr(III) was 26.7 mg g−1 under ultrasonic dispersing. The potential application of p-toluenesulfonylamide-modified silica gel for simultaneous preconcentration of trace chromium, copper, lead and zinc from two standard reference materials and two food samples was performed with satisfactory results.

Quantitative analysis of trace chromium in blood samples. Combination of the advanced oxidation process with catalytic adsorptive stripping voltammetry.

A new method for pretreating blood samples for trace Cr analysis is described. The advanced oxidation process (AOP with H2O2 and 5.5-W UV irradiation for 60 min) is used to remove biological/organic species for subsequent analysis. Prior to the AOP pretreatment, acid (HNO3) is used at pH 3.0 to inhibit the enzyme catalase in the blood samples. Catalytic adsorptive stripping voltammetry at a bismuth film electrode gives a Cr concentration of 6.0 +/- 0.3 ppb in the blood samples. This concentration was confirmed by dry-ashing the blood samples and subsequent analysis by atomic absorption spectroscopy. This current method may be used to monitor chromium, a trace metal in humans, and the efficacy and safety of chromium supplements as adjuvant therapy for diabetes.

Coastal Pollution Mitigation with Lime and Zero Valent Iron

The Taiwan Strait region has many miles of coastline, and the Taiwan Straits Tunnel (TST) project faces many potential pollution problems as construction proceeds through sensitive areas. Conventional approaches for pollution mitigation require further examination. The recent development of nanoscale particle technology has shown distinct advantages for contaminant attenuation and ground improvement. This paper is focused on trace metals and is part of the overall effort to develop the nanoscale particle technology. Trace metals in ground and surface waters represent a continued threat to human and ecological health. One of the difficulties in removing toxic concentrations of trace metals from solution is the variable oxidation state and amphoteric nature of multiple constituents. In particular, while cationic metals (e.g., Pb2+, Cd2+, Ni2+) may be rendered less mobile under high pH conditions, anionic metals (e.g., AsO4 3−, CrO4 2−, SeO4 2−)may become more mobile. The objective of this research was to evaluate the sorption of both cationic and anionic trace elements, including arsenic (As), cadmium (Cd), chromium (Cr) and selenium (Se) under batch conditions. Mixtures of a local residual soil were tested alone and in combination with lime and zero valent iron. It was hypothesized that lime would raise the pH and precipitate positively charged metals while zero valent iron would create reducing conditions favorable to the immobilization of negatively charged metals. Results indicate that the use of lime and/or zero valent iron can increase the sorption capacity of soil. Compared to the baseline soil, sorption capacity increased with addition of lime for arsenic and cadmium while it decreased for chromium and selenium. In the case of zero valent iron addition, sorption capacity increased for cadmium, chromium and selenium, while showing no change for arsenic. When both lime and zero valent iron were used, the sorption capacity increased for all metals tested. These results suggest that the combined use of lime and zero valent iron may serve as an alternative treatment technology for removing trace metals from contaminated water systems.

Studies and Application of Catalytic Kinetic Spectrophotometric Determination of Trace Chromium(VI) Sensitized by Microemulsion Medium

A new catalytic kinetic spectrophotometric method for the determination of trace amount of chromium (VI) in microemulsion medium has been developed. The method is based on the catalytic effect of chromium (VI) on the oxidation of nuclear fast red in the presence of Tween-80 microemulsion and HAc-NaAc buffer solution (pH = 5.2). The linear ranges are in the range of 0 approximately 0.0480 microg mL(-1) of Cr (VI) at 528 nm and the detection limit is 1.56x10(-9)g mL(-1). The method has been applied in determination of Cr (VI) in water and food samples with satisfactory results. The relative standard deviation is less than 4.6 % and the recovery is 93.5 approximately 104 %.

Measurement of concentrations of trace metals in arable soils with animal manure application using instrumental neutron activation analysis and the concentrated acid digestion method

An experiment was conducted to determine the accumulation of trace metals, zinc (Zn), chromium (Cr), manganese (Mn) and iron (Fe), in three types of arable soils (Brown Lowland soil, Andosol and Brown Forest soil) amended with chemical fertilizers (CHF), cattle farmyard manure (CFM) and pig farmyard manure (PFM) over a 5-year period. Two methods were used to determine the total amount of trace metals: the instrumental neutron activation analysis (INAA), as a non-destructive measurement, and the concentrated acid digestion method (CADM), as a destructive measurement. Results of soil analyses using both INAA and CADM indicated that PFM application resulted in a considerable increase in the amount of Zn in arable soils compared with CHF application, unlike CFM application. Results obtained from the two methods were not fully in agreement for Cr. Based on INAA, soil accumulation of Cr from CFM and PFM applications was not significant in any soil type. In contrast, based on CADM, Cr accumulation was relatively higher in the Brown Forest soil with PFM than with CHF application. The soil types and treatments exerted various effects on Cr, Mn and Fe concentrations. The 5-year application of animal manure did not result in a considerable increase in Cr, Mn and Fe concentrations in soils, whereas longer-term application may lead to a gradual accumulation of Cr and Fe depending on the soil and manure types. The use of CADM in the present study may not always be adequate to assess the accumulation of trace metals in soils amended with CFM and PFM because of the conditions of the measurements, such as sensitivity, dilution level or type of instrument, and not because of the digestion method. The types of soil and manure affect trace metal accumulation in arable soils, and elements in the manure relate to the ability of soils to retain trace metals. It is important that the results of non-destructive and destructive measurements, obtained using INAA and CADM, be evaluated properly.

Flow injection direct spectrophotometric assay for the speciation of trace chromium(III) and chromium(VI) using chromotropic acid as chromogenic reagent

A new rapid and sensitive FI assay is reported for the simultaneous direct spectrophotometric determination of trace Cr(VI) and Cr(III) in real samples. The method is based upon the reaction of Cr(VI) with chromotropic acid (CA) in highly acidic medium to form a water-soluble complex ( λ max = 370 nm). Cr(III) reacts with CA only after its on-line oxidation to Cr(VI) by alkaline KIO 4. The determination of each chromium species in the sample was achieved by absorbance differences. The calibration curves were linear over the range 3–4000 μg l −1 and 30–1200 μg l −1 for Cr(VI) and Cr(III), respectively, while the precision close to the quantitation limit was satisfactory in both cases ( s r = 3.0% for Cr(VI) and 4.0% for Cr(III) ( n = 10) at 10 and 50 μg l −1 level, respectively). The method developed proved to be adequately selective and sensitive ( c L = 1 and 10 μg l −1 for Cr(VI) and Cr(III), respectively). The application of the method to the analysis of water samples (tap and mineral water) gave accurate results based on recovery studies (93–106%). Analytical results of real sample analysis were in good agreement with certified values.

Application of Dithizone-Modified TiO2 Nanoparticles in the Preconcentration of Trace Chromium and Lead from Sample Solution and Determination by Inductively Coupled Plasma Atomic Emission Spectrometry

A new method using dithizone-modified TiO2 nanoparticles (nanometer TiO2-DZ) as solid-phase extractant has been developed for the simultaneous preconcentration of trace amounts of chromium and lead prior to their measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The preconcentration conditions of the analytes, including the effects of pH, sample flow rate and volume, elution conditions and interfering ions on the recovery of the analytes were investigated. At pH 5, the adsorption capacity of the nanometer TiO2-DZ was found to be 5.8 mg g−1 and 22.5 mg g−1 for Cr and Pb, respectively. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr and Pb were 0.38 and 1.72 ng mL−1, respectively. The proposed method was applied to the determination of trace chromium and lead in foodstuffs, plants and water samples with satisfactory results.

Mineral Contents of Aloe vera Leaf Gel and Their Role on Streptozotocin-Induced Diabetic Rats

The role of some inorganic elements like vanadium, zinc, sodium, potassium, calcium, copper, manganese, and traces of chromium in the improvement of impaired glucose tolerance and their indirect role in the management of diabetes mellitus are being increasingly recognized. In traditional methods, medicinal plants are being used, which contain both organic and inorganic constituents. In the present study, an attempt has been made to analyze the inorganic elements present in Aloe vera leaf gel and their role on diabetes-related biochemical alterations in experimental rats. Special emphasis was given to the inorganic parts by carefully preparing ash of the leaf gel. The results clearly indicate the presence of several hypoglycemic-activity-possessing elements in the gel. The ash treatment also resulted in hypoglycemic action. In conclusion, the presence of various inorganic trace elements in the gel might account for the hypoglycemic nature of the plant.

Growth rate hysteresis of a potassium dihydrogen phosphate (KDP) crystal in the presence of traces of impurity

The growth rate of the (1 0 0) face of a single potassium dihydrogen phosphate (KDP) crystal was investigated in the presence of traces of chromium (III) up to 5 ppm in a flow cell at different rates of changes of supercooling (±0.1 and ±0.2 °C/min). Hysteresis in crystal growth rates in the presence of chromium (III) was induced by decreasing and increasing the supercooling. The growth hysteresis is described qualitatively by a mathematical model considering the pinning mechanism of Cabrera and Vermilya, the two-dimensional Gibbs–Thompson effect on step movement and by assuming slow adsorption of impurity species on the crystal surface.