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1.
Crosslinked chitosan-bound FeC nanoparticles (CCBFeCNP) were prepared, and the adsorptive behavior of Cr(III) and Cr(VI) on
CCBFeCNP were assessed. At pH 6.0–10.0, CCBFeCNP is selective towards Cr(III) but hardly selective towards Cr(VI). The retained
Cr(III) is subsequently eluted with 0.5 mol L−1 HCl. Total chromium is determined after reduction of Cr(VI) to Cr(III) by ascorbic acid. A new method of flow injection using
a micro-column packed with CCBFeCNP as solid phase extractant has been developed for speciation of Cr(III) and Cr(VI) in water
samples, followed by flame atomic absorption spectrometry. The effects of pH, sample flow rate and volume, elution solution
and interfering ions on the recoveries of Cr(III) were systematically investigated. Under optimum conditions, the adsorption
capacity of CCBFeCNP for Cr(III) is 10.5 mg g−1 at pH 7.5. The procedure presented was applied to chromium speciation in water samples, and the results were satisfactory. 相似文献
2.
A study was undertaken to evaluate Saccharomyces cerevisiae as a substrate for the biosorption of Cr(III) and Cr(VI) aiming to the selective determination of these species in aqueous solutions. The yeast cells were covalently immobilised on controlled pore glass (CPG), packed in a minicolumn and incorporated in an on-line flow injection system. The effect of chemical and physical variables affecting the biosorption process was tested in order to select the optimal analytical conditions for the Cr retention by S. cerevisiae. Cr(III) was retained by the immobilised cells and Cr(VI) were retained by CPG. The speciation was possible by selective and sequential elution of Cr(III) with 0.05 mol L−1 HCl and 2.0 mol L−1 HNO3 for Cr(VI). The influence of some concomitant ions up to 20 mg L−1 was also tested. Quantitative determinations of Cr were carried out by means of inductively coupled plasma optical emission spectrometry (ICP OES). Preconcentration factors of 12 were achieved for Cr(III) and 5 for Cr(VI) when 1.7 mL of sample were processed reaching detection limits of 0.45 for Cr(III) and 1.5 μg L−1 for Cr(VI). The speciation of inorganic Cr in different kinds of natural waters was performed following the proposed method. Spiked water samples were also analysed and the recoveries were in all cases between 81 and 103%. 相似文献
3.
An isotope dilution method has been developed for the speciation analysis of chromium in natural waters which accounts for species interconversions without the requirement of a separation instrument connected to the mass spectrometer. The method involves (i) in-situ spiking of the sample with isotopically enriched chromium species; (ii) separation of chromium species by precipitation with iron hydroxide; (iii) careful measurement of isotope ratios using an inductively coupled plasma mass spectrometer (ICP-MS) with a dynamic reaction cell (DRC) to remove isobaric polyatomic interferences. The method detection limits are 0.4 μg L−1 for Cr(III) and 0.04 μg L−1 for Cr(VI). The method is demonstrated for the speciation of Cr(III) and Cr(VI) in local nullah and synthetically spiked water samples. The percentage of conversion from Cr(III) to Cr(VI) increased from 5.9% to 9.3% with increase of the concentration of Cr(VI) and Cr(III) from 1 to 100 μg L−1, while the reverse conversion from Cr(VI) to Cr(III) was observed within a range between 0.9% and 1.9%. The equilibrium constant for the conversion was found to be independent of the initial concentrations of Cr(III) and Cr(VI) and in the range of 1.0 (at pH 3) to 1.8 (at pH 10). The precision of the method is better than that of the DPC method for Cr(VI) analysis, with the added bonuses of freedom from interferences and simultaneous Cr(III) determination. 相似文献
4.
Grabarczyk M 《Analytical and bioanalytical chemistry》2008,390(3):979-986
A simple and fast catalytic adsorptive stripping voltammetric procedure for trace determination of Cr(VI) in natural samples
containing high concentrations of humic substances has been developed. The procedure for chromium determination in the presence
of DTPA and nitrates was employed as the initial method. In order to enhance the selectivity vs. Cr(III) the measurements
were performed at 40°C. Interference from dissolved organic matter such as humic and fulvic acids was drastically decreased
by adding Amberlite XAD-7 resin to the voltammetric cell before the deaeration step. The whole procedure was applied to a
single cell, which allowed monitoring of the voltammetric scan. Optimum conditions for removing humic and fulvic acids due
to their adsorption on XAD-7 resin were evaluated. The use of XAD-7 resin also minimize interferences from various cationic,
anionic, and nonionic surfactants. The calibration graph for Cr(VI) for an accumulation time of 30 s was linear in the range
5 × 10−10 to 5 × 10−8 mol L−1. The relative standard deviation for determination of Cr(VI) at a concentration of 1 × 10−8 mol L−1 was 3.5% (n = 5). The detection limit estimated from 3 times the standard deviation for low Cr(VI) concentrations and an accumulation
time of 30 s was about 1.3 × 10−10 mol L−1. The proposed method was successfully applied to Cr(VI) determination at trace levels in soil samples. 相似文献
5.
《International journal of environmental analytical chemistry》2012,92(4):375-381
An inductively coupled plasma atomic emission spectrometric (ICP-AES) method was developed for speciation and simultaneous determination of Cr and As, since these two analytes are commonly determined in various water samples in order to assess their toxicity. The objective of this research was to study the speciation of Cr(III), Cr(VI) in the presence of As(III) and/or As(V) using solid phase extraction (SPE) and ICP-AES. For these measurements, four spectral lines were used for each analyte with the purpose of selecting the most appropriate for each element. Finally with the use for first time of a cation-exchange column filled with benzosulfonic acid and elution with HCl, the speciation in solutions which contained [Cr(III)?+?Cr(VI)?+?As(V)] and [Cr(III)?+?Cr(VI)?+?As(III)] was examined. It was demonstrated that the separation of the two chromium species is almost quantitative and the simultaneous determination of chromium species and total arsenic analytes is possible, with very good performance characteristics. The estimated limits of detection for Cr(III), Cr(VI), As(III) and/or As(V) were 0.9?µg?L?1, 1.1 µg?L?1, 4.7 µg?L?1 and 4.5 µg?L?1 respectively, the calculated relative standard deviations (RSDs) were 3.8%, 4.1%, 5.2% and 5.1% respectively, and finally the accuracy of the methods was estimated using a certified aqueous reference material and found to be 5.6% and 4.8% for Cr(III) and Cr(VI) respectively. The method was applied to the routine analysis of various water samples. 相似文献
6.
An isotope dilution mass spectrometric (IDMS) method, using the formation of positive thermal ions, was developed for Cr(III)
and Cr(VI) speciation in aerosol particles. Cr(III) and Cr(VI) spike species, enriched in 53Cr, were applied for the isotope dilution step. After leaching of filter collected aerosol samples by an alkaline solution
at pH 13, species separation was carried out by extraction with a liquid anion exchanger in methyl isobutyl ketone. Cr(VI)
in the organic phase was re-extracted into an ammoniacal solution and chromium was then isolated from both fractions of species
by electrodeposition. Detection limits of 30 pg/m3 for Cr(III) and of 8 pg/m3 for Cr(VI) were achieved in atmospheric aerosols for volumes of air samples of about 120 m3. These low detection limits allowed the determination of chromium species in continental aerosol particles in dependence
on different seasons. The Cr(III) /Cr(VI) ratio was always found to be about 0.3 whereas dust from soil erosion, which is
probably the primary source of chromium in the atmosphere, showed higher ratios. This indicates that chromium is oxidized
in the atmosphere. The accuracy of the method was demonstrated in two interlaboratory comparisons of Cr(VI) determinations
in welding dust samples. The IDMS method also contributed to the certification of a corresponding standard reference material
organized by the Standard Reference Bureau of the European Union. Chromium speciation, including the determination of elemental
chromium Cr(0), was carried out in aerosols of different welding processes for stainless steel. These analyses showed distinct
differences in the distribution of chromium species in the welding process and can be used as an exact calibration method
for routine methods in this important field of monitoring corresponding working places.
Received: 19 August 1996/Revised: 24 September 1996/Accepted: 28 September 1996 相似文献
7.
Mohammad Ali Karimi Rasul Shahin Sayed Zia Mohammadi Abdolhamid Hatefi‐Mehrjardi Javad Hashemi Javad Yarahmadi 《中国化学会会志》2013,60(11):1339-1346
A new solid phase extraction (SPE) method has been developed for the speciation of Cr(III) and Cr(VI). This method is based on the adsorption of Cr(VI) on modified alumina‐coated magnetite nanoparticles (ACMNPs). Total chromium in different samples was determined as Cr(VI) after oxidation of Cr(III) to Cr(VI) using H2O2. The chromium concentration has been determined by flame atomic absorption spectrometric (FAAS) technique and amount of Cr(III) was calculated by substracting the concentration of Cr(VI) from total chromium concentration. The effect of parameters such as pH, amount of adsorbent, contact time, sample volume, eluent type, H2O2 concentration and cetyltrimethylammonium bromide (CTAB) concentration as modifier on the quantitative recovery of Cr(VI) were investigated. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation (RSD) of Cr(VI) were 140 (for 350 mL of sample solution), 0.083 ng mL?1, 0.1‐10.0 ng mL?1 and 4.6% (for 5.0 ng mL?1, n = 7), respectively. This method avoided the time‐consuming column‐passing process of loading large volume samples in traditional SPE through the rapid isolation of CTAB@ACMNPs with an adscititious magnet. The proposed method was successfully applied to the determination and speciation of chromium in different water and wastewater samples and suitable recoveries were obtained. 相似文献
8.
We report an in-situ harvesting technique of electron-hole (e−-h+) carriers (e.g., the defect electrons in the O2 − matrix and the self-trapped holes, Si–O−–Si) generated during sol-gel processing. In the absence of redox species, the e−-h+ centers created during room temperature sol-gel polycondensation steps are quickly annihilated and deactivated. However,
when Cr(VI) ions are pre-dispersed in sol-gel solutions, the ejected electrons can be effectively harvested for the reduction
of Cr(VI) to Cr(III) ions which are encapsulated in the silica gel matrix. The Cr(VI) ions, the possible intermediate oxidation
states of chromium ions such as Cr(V) and/or Cr(IV), and the stable Cr(III)-hole complexes in the sol-gel matrix are investigated
using uv-visible spectroscopy, electron paramagnetic resonance spectroscopy, and cyclic voltammetry. The chemical stability
of Cr(VI) and Cr(III) in sol-gel networks is compared to that in aqueous solutions. The results indicate that the utilization
of e−-h+ carriers generated in the sol-gel can be an effective and selective means for investigating the redox process of Cr(VI) and
encapsulating the stable Cr(III) ions in the confined sol-gel environments. 相似文献
9.
Abdel-Aziz Youssef El-Sayed Ebtesam Ahmad Saad Basheer Mohamed Mohamed Ibrahime Mohamed Tarek Mohamed Zaki 《Mikrochimica acta》2000,135(1-2):19-27
Simple, rapid, sensitive and selective methods for the determination of Cr(III) and W(VI) with flavonol derivatives in the
presence of surface-active agents are proposed. In the pH ranges 3.4–4.2 and 1.9–2.5, the molar absorptivities of Cr(III)-morin-emulsifier
S (EFA) and W(VI)-morin-polyvinylpyrrolidone (PVP) systems are 1.13×105 and 2.13×104 L mol−1 cm−1 at 435 and 415 nm, respectively. The Cr(III)-quercetin-PVP and W(VI)-quercetin-cetylpyridinium bromide (CPB) systems are
formed in the pH ranges 4–4.6 and 2.2–2.8 with molar absorptivities 1.02×105 and 9.02×104 L. mol−1 cm−1 at 441 and 419 nm, respectively. The linear dynamic ranges for the determination of Cr(III) and W(VI) with morin in the presence
of EFA and PVP are 0.03–0.46 and 0.71–8.1 μg mL−1, respectively. The corresponding ranges with quercetin are 0.04–0.54 and 0.14–2.1 μg mL−1 of Cr(III) and W(VI), respectively. The r.s.d (n = 10) for the determination of 0.25 and 3.7 μg mL−1 of Cr(III) and W(VI) with morin and their detection limits are 0.88 and 0.99% and 0.016 and 0.63 μg mL−1, respectively. Using quercetin, the r.s.d (n = 10) for 0.22 and 1.2 μg mL−1 of Cr(III) and W(VI) and their detection limits are 0.92 and 0.91% and 0.015 and 0.08 μg mL−1, respectively. The critical evaluation of the proposed methods is performed by statistical analysis of the experimental data.
The proposed methods are applied to determine Cr in steel, non-ferrous alloys, wastewater and mud filtrate and to the determination
of W in steel.
Received March 8, 1999. Revision January 21, 2000. 相似文献
10.
Birsen Demirata 《Mikrochimica acta》2001,136(3-4):143-146
A method is described for the quantitative preconcentration and separation of trace chromium in water by adsorption on melamine-urea-formaldehyde
resin. Cr(VI) is enriched from aqueous solutions on the resin. After elution the Cr(VI) is determined by FAAS. The capacity
of the resin is maximal at ∼ pH 2. Total chromium can be determined by the method after oxidation of Cr(III) to Cr(VI) by
hydrogen peroxide. The relative standard deviations (10 replicate analyses) for 10 mg/L levels of Cr(VI), Cr(III) and total
chromium were 1.5, 3.5 and 2.8% respectively. The procedure has been applied to the determination and speciation of chromium
in lake water, tap water and chromium-plating baths. 相似文献
11.
Juan C. Vidal José M. Sanz Juan R. Castillo 《Fresenius' Journal of Analytical Chemistry》1992,344(6):234-241
Summary The pyrolysed graphite L'vov platform of a tube furnace is considered as an electrode for the electrodeposition and speciation of chromium by electrothermal atomisation atomic absorption spectrometry (ETA-AAS). Firstly, a preliminary study of the Cr(VI)/Cr(III) voltammetric behavior at pH 4.70 on a glassy-carbon electrode is carried out. Secondly, the L'vov platform is used as a cathodic macro-electrode for the selective preconcentration of Cr(VI)/Cr(III) on a mercury film. Speciation of Cr(VI)/Cr(III) is carried out on the basis of the electrolysis potential (Ee): at pH 4.70 and Ee=–0.30 V, only Cr(VI) is reduced to Cr(III) and accumulated as Cr(OH)3 by adsorption on a mercury film; at Ee=–1.80 V both Cr(VI) and Cr(III) are accumulated forming an amalgam with added mercury(II) ions. Once the film has been formed, the platform is transferred to a graphite tube to atomise the element. The reliability of the method was tested for the speciation of chromium in natural waters and it proves to be highly sensitive thanks to the electroanalytical step. In all samples, the Cr(VI) concentration was less than the detection limit (0.15 ng ml–1), and the concentration of Cr(III) agrees with those of total chromium. The analytical recovery of Cr(VI) added to water samples [3.50 ng ml–1 of Cr(VI)] was 105±6.2%. 相似文献
12.
The possibility of using moss (Funaria hygrometrica), immobilized in a polysilicate matrix as substrate for speciation of Cr(III) and Cr(VI) in various water samples has been investigated. Experiments were performed to optimize conditions such as pH, amount of sorbent and flow rate, to achieve the quantitative separation of Cr(III) and Cr(VI). During all the steps of the separation process, Cr(III) was selectively sorbed on the column of immobilized moss in the pH range of 4-8 while, Cr(VI) was found to remain in solution. The retained Cr(III) was subsequently eluted with 10 ml of 2 mol l−1 HNO3. A pre-concentration factor of about 20 was achieved for Cr(III) when, 200 ml of water was passed. The immobilized moss was packed in a home made mini-column and incorporated in flow injection system for obtaining calibration plots for both Cr(III) and Cr(VI) at low ppb levels that were compared with the plots obtained without column. After separation, the chromium (Cr) species were determined by inductively coupled plasma mass spectrometry (ICP-MS) and flame atomic absorption spectrometry (FAAS). The sorption capacity of the immobilized moss was found to be ∼11.5 mg g−1 for Cr(III). The effect of various interfering ions has also been studied. The proposed method was applied successfully for the determination of Cr(III) and Cr(VI) in spiked and real wastewater samples and recoveries were found to be >95%. 相似文献
13.
Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer-scale TiO2 particles) was prepared by a sol-gel method and characterized by X-ray diffraction and scanning electron microscopy. The adsorptive behavior of Cr(III) and Cr(VI) on immobilized nanometer TiO2 was assessed. Cr(III) was selectively sorbed on immobilized nanometer TiO2 in the pH range of 7-9, while Cr(VI) was found to remain in solution. A sensitive and selective method has been developed for the speciation of chromium in water samples using an immobilized nanometer TiO2 microcolumn and inductively coupled plasma atomic emission spectrometry. Under optimized conditions (pH 7.0, flow rate 2.0 mL/min), Cr(III) was retained on the column, then eluted with 0.5 mol/L HNO3 and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid. The adsorption capacity of immobilized nanometer TiO2 for Cr(III) was found to be 7.04 mg/g. The detection limit for Cr(III) was 0.22 ng/mL and the RSD was 3.5% (n = 11, c = 100 ng/ mL) with an enrichment factor of 50. The proposed method has been applied to the speciation of chromium in water samples with satisfactory results. 相似文献
14.
Celal Duran Mustafa Soylak Volkan Numan Bulut Ali Gundogdu Mehmet Tufekci Latif Elci Hasan Basri Senturk 《中国化学会会志》2007,54(3):625-634
A method for speciation of Cr(III) and Cr(VI) in real samples has been developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its pyrrolidinedithiocarbamate (APDC) complex by using a column containing Amberlite XAD–2000 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO4. Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of pH, flow‐rate, adsorption and batch capacity and effect of various metal cations and salt anions on the sorption onto the resin were investigated. The adsorption is quantitative in the pH range of 1.5–2.5, and Cr(VI) ion was desorbed by using H2SO4 in acetone. The recovery of Cr(VI) was 97 ± 4 at a 95% confidence level. The highest preconcentration factor was 80 for a 200 mL sample volume. The adsorption and batch capacity of sorbent were 7.4 and 8.0 mg g?1 Cr(VI), respectively, and loading half time was 5.0 min. The detection limit of Cr(VI) is 0.6 μg/L. The procedure has been applied to the determination and speciation of chromium in stream water, tap water, mineral spring water and spring water. Also, the proposed method was applied to total chromium preconcentration in microwave digested moss and rock samples with satisfactory results. The developed method was validated with CRM‐TMDW‐500 (Certified Reference Material Trace Metals in Drinking Water) and BCR‐CRM 144R s (Certified Reference Material Sewage Sludge, Domestic Origin) and the results obtained were in good agreement with the certified values. The relative standard deviations were below 6%. 相似文献
15.
Shayessteh Dadfarnia Ali Mohammad Haji Shabani Masood Reza Shishebor Kolsom Hosseini Cisakht 《International journal of environmental analytical chemistry》2013,93(13):1320-1328
A sensitive and simple method for determination of chromium species after separation and preconcentration by solid phase extraction (SPE) has been developed. For the determination of the total concentration of chromium in solution, Cr(VI) was efficiently reduced to Cr(III) by addition of hydroxylamine and Cr(III) was preconcentrated on a column of immobilised ferron on alumina. The adsorbed analyte was then eluted with 5?mL of hydrochloric acid and was determined by flame atomic absorption spectrometery. The speciation of chromium was affected by first passing the solution through an acidic alumina column which retained Cr(VI) and then Cr(III) was preconcentrated by immobilised ferron column and determined by FAAS. The concentration of Cr(VI) was determined from the difference of concentration of total chromium and Cr(III). The effect of pH, concentration of eluent, flow rate of sample and eluent solution, and foreign ions on the sorption of chromium (III) by immobilised ferron column was investigated. Under the optimised conditions the calibration curve was linear over the range of 2–400?µg?L?1 for 1000?mL preconcentration volume. The detection limit was 0.32?µg?L?1, the preconcentration factor was 400, and the relative standard deviation (%RSD) was 1.9% (at 10?µg?L?1; n?=?7). The method was successfully applied to the determination of chromium species in water samples and total chromium in standard alloys. 相似文献
16.
Halil İbrahim Ulusoy Ramazan Gürkan Öznur Yılmaz Mehmet Akçay 《Journal of Analytical Chemistry》2012,67(2):131-139
A sensitive and selective method has been developed for the determination of chromium in water samples based on using cloud
point extraction (CPE) preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Cr(III) ions with Brilliant Cresyl Blue (BCB) in the presence of non-ionic surfactant Triton X-114. Under the optimum conditions, the preconcentration of 50 mL of water
sample in the presence of 0.5 g/L Triton X-114 and 1.2 × 10−5 M BCB permitted the detection of 0.42 μg/L chromium(III). The calibration graph was linear in the range of 1.5–70 μg/L, and
the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Cr(III) in water samples
and certified water samples. In addition, the developed CPE-FAAS method was also used for speciation of the inorganic chromium
species after reduction of Cr(VI) to Cr(III) using a thiosulphate solution of 120 mg/L in the presence of Hg(II) ion as a
stabilizer. 相似文献
17.
A new melamine based polymeric sequestering resin was prepared for preconcentration and separation of hexavalent chromium from water, and its sequestering action was investigated. The water-insoluble, cross-linked sequestering resin was formed by reaction with bromosuccinic acid and cross-linking of melamine. The active sequestering group on the resin is NH-(Succinic acid) or salt thereof. The resulting chelating resin was characterized by infrared spectra. The newly prepared resin quantitatively retained Cr(VI) at pH 2.0-4.0 when the flow rate was maintained between 1 and 5 ml min−1. The retained Cr(VI) was instantaneously eluted with 25 ml of 0.1 M NaOH. The chromium species were determined by a flame atomic absorption spectrometer. The limits of detection for Cr(VI) and Cr(III) were found to be 5.3 and 4.2 μg l−1, respectively. The precision and accuracy of the proposed procedure was checked by the use synthetic and reference steel samples. The established preconcentration method was successfully applied to the determination and selective separation of Cr(VI) in electroplating industry wastewater. Total concentrations determined by the spectrophotometric method (110.3±0.6 g l−1 Cr(VI) and 1.2±0.3 g l−1 Cr(III)) are compared with those found by FAAS and the obtained results (110.4±1.8 g l−1 Cr(VI) and 1.4±0.5 g l−1 Cr(III)) show good agreement. 相似文献
18.
K. E. Collins Pierina S. Bonato Cielita Archundia Maria Eliana L. R. de Queiroz Carol H. Collins 《Chromatographia》1988,26(1):160-162
Summary Chromium can be present in aqueous solution as Cr(VI) or in monomeric, dimeric, trimeric and higher polymeric forms of Cr(III). Many monomeric forms of Cr(III) are possible, with the water molecules of Cr(H2O)
6
3+
substituted by anionic or neutral species. This proliferation of Cr(III) species makes the complete speciation of chromium a continuing challenge to the analyst. A simple and effective cation exchange procedure for the separation of various of these species uses a small glass column containing 1 mL of pre-treated cation exchange resin (Na+ form). Stepwise elution with solutions of perchloric acid, Ca2+ (pH=2) and La3+ (pH=2) separates Cr(VI) and seven Cr(III) species from CrX3 to tetramer. Radiometric (Cr-51), spectrophotometric and other detection methods can be employed; the use of radiochromium gives the lowest detection limit. 相似文献
19.
Elahe Kazemi Shayessteh Dadfarnia Fatemeh Izadi 《International journal of environmental analytical chemistry》2017,97(11):1080-1093
A selective, simple and fast dispersive micro solid phase extraction method using magnetic graphene oxide (GO) as an efficient sorbent has been developed for the extraction, separation and speciation analysis of chromium ions. The method is based on different adsorption behaviour of Cr(VI) and Cr(III) species onto magnetic GO in aqueous solutions which allowed the selective separation and extraction of Cr(VI) in the pH range of 2.0–3.0. The retained Cr(VI) ions by the sorbent were eluted using 0.5 mL of 0.5 mol L?1 nitric acid solution in methanol and determined by ?ame atomic absorption spectrometry. Total chromium content was determined after the oxidation of Cr(III) to Cr(VI) by potassium permanganate. All effective parameters on the performance of the extraction process were thoroughly investigated and optimised. Under the optimised conditions, the method exhibited a linear dynamic range of 0.5–50.0 µg L?1 with a detection limit of 0.1 µg L?1 and pre-concentration factor of 200. The relative standard deviations of 3.8% and 4.6% (n = 8) were obtained at 25.0 µg L?1 level of Cr(VI) for intra- and inter-day analysis, respectively. The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in environmental water samples. 相似文献
20.
A speciation procedure has been established for the flame atomic absorption spectrometric determination of Cr(III) and Cr(VI) based on coprecipitation of Cr(III) by using praseodymium(III) hydroxide (Pr(OH)3) precipitate. In the presented system, Cr(III) was quantitatively (>95%) recovered at the pH range of 10.0?C12.0 on Pr(III) hydroxide, while the recoveries of Cr(VI) were below 10%. The method was applied to the determination of the total chromium after reduction of Cr(VI) to Cr(III) by using hydroxylamine hydrochloride. The concentration of Cr(VI) is calculated by difference of total chromium and Cr(III) levels. The analytical parameters including pH of the aqueous medium, amount of Pr(III), centrifugation speed, sample volume were optimized. The influences of matrix ions were also investigated. The method was validated by the analysis of TMDA 70 fortified lake water certified reference material. The method was applied to the speciation of chromium in water samples. 相似文献