共查询到20条相似文献,搜索用时 31 毫秒
1.
Ph. Goodall 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):5-13
The development of a spectrophotometric method for the determination of hydrogen peroxide in uranyl nitrate solutions is reported.
The method involves the measurement of the absorbance at 520 nm of a vanadyl peroxide species. This species was formed by
the addition of a reagent consisting of vanadium (V) (50 mmol·dm−3) in dilute sulphuric acid (2 mol·dm−3 H2SO4). This reagent, after dilution, was also used as an extractant for organic phase samples. The method is simple and robust
and tolerant of nitric acid and U(VI). Specificity and accuracy were improved by the application of solid phase extraction
techniques to remove entrained organic solvents and Pu(IV). Reverse phase solid phase extraction was used to clean-up aqueous
samples or extracts which were contaminated with entrained solvent. A solid phase extraction system based upon an extraction
chromatography system was used to remove Pu(IV). Detection limits of 26 μmol·dm−3 (0.88 μg·cm−3) or 7 μmol·dm−3 (0.24 μg·cm−3) for, respectively, a 1 and 4 cm path length cell were obtained. Precisions of RSD=1.4% and 19.5% were obtained at the extremes
of the calibration curve (5 mmol·dm−3 and 50 μmol·dm−3 H2O2, 1 cm cell). The introduction of the extraction and clean-up stages had a negligible effect upon the precision of the determination.
The stability of an organic phase sample was tested and no loss of analyte could be discerned over a period of at least 5
days. The presence of trace levels of reductants interfered with the determination, e.g., hydrazine (<2 mmol·dm−3), but this effect was ameliorated by increasing the concentration of the colormetric reagent. 相似文献
2.
Vibha Saxena Vinay Shirodkar Rajiv Prakash 《Journal of Solid State Electrochemistry》2000,4(4):234-236
A device has been developed for the measurement of copper(II) ions (Cu2+) in aqueous medium. The device reported here is an electrochemical transistor which consists of two platinum electrodes separated
by 100 μm spacing and bridged with an anodically grown film of polycarbazole. Polycarbazole film (undoped form) is observed
to be highly selective for the Cu(II) ions. In a completed device, the conductivity of the polycarbazole film changes on addition
of Cu(II) ions. The change in conductivity is attributed to the conformational changes in the polymer phase on occupation
of the Cu(II) ions, without affecting electron/proton transfer. The device turns on by adding 2.5 × 10−6 M Cu(II) ions and reaches a saturation region beyond 10−4 M Cu(II) ion concentrations. In the above concentration range, the device response [I
D vs. log Cu(II) ion concentration] is linear. The selectivity of the device for other metal ions such as Cu(I), Ni(II), Co(II),
Fe(II), Fe(III), Zn(II) and Pb(II) is also studied.
Received: 6 April 1999 / Accepted: 20 August 1999 相似文献
3.
A new ternary ion-association complex of tungsten(VI), 4-nitrocatechol (NC), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (Thiazolyl Blue, MTT) was obtained and studied using an extraction-spectrophotometric method. The optimum pH, reagent
concentrations, and extraction time were determined. The composition of the complex was found to be W(VI): NC: MTT = 1: 2:
2. The extraction process was investigated quantitatively and the key constants were calculated. The molar absorptivity of
the chloroform extract at λmax = 415 nm was 2.8 × 104 dm3 mol−1 cm−1, and the Beer’s law was obeyed up to 8.8 μg cm−3 tungsten(IV). The limit of detection and limit of quantification were calculated to be 0.27 μg cm−3 and 0.92 μg cm−3, respectively. The effect of foreign ions and reagents was studied and a competitive method for determination of tungsten
in products from ferrous metallurgy was developed. The residual standard deviation and the relative error were 0.53 % and
0.2 %, respectively. 相似文献
4.
Pinheiro SC Descalzo AB Raimundo IM Orellana G Moreno-Bondi MC 《Analytical and bioanalytical chemistry》2012,402(10):3253-3260
This paper describes the synthesis and characterization of a fluorescent ion-imprinted polymer (IIP) for selective determination
of copper ions in aqueous samples. The IIP has been prepared using a novel functional monomer, 4-[(E)-2-(4′-methyl-2,2′-bipyridin-4-yl)vinyl]phenyl methacrylate (abbreviated as BSOMe) that has been spectroscopically characterized
in methanolic solution, in the absence and in the presence of several metal ions, including Cd(II), Cu(II), Hg(II), Ni(II),
Pb(II), and Zn(II). The stability constant (2.04 × 108 mol−2 l2) and stoichiometry (L2M) of the BSOMe complex with Cu(II) were extracted thereof. Cu(II)-IIPs were prepared by radical polymerization using stoichiometric
amounts of the fluorescent monomer and the template metal ion. The resulting cross-linked network did not show any leaching
of the immobilized ligand allowing determination of Cu(II) in aqueous samples by fluorescence quenching measurements. Several
parameters affecting optosensor performance have been optimized, including sample pH, ionic strength, or polymer regeneration
for online analysis of water samples. The synthesized Cu(II)-IIP exhibits a detection limit of 0.04 μmol l−1 for the determination of Cu(II) in water samples with a reproducibility of 3%, exhibiting an excellent selectivity towards
the template ion over other metal ions with the same charge and close ionic radius. The IIP-based optosensor has been repeatedly
used and regenerated for more than 50 cycles without a significant decrease in the luminescent properties and binding affinity
of the sensing phase. 相似文献
5.
Yasar Arafat Abbasi Akbar Ali Muhammad Haleem Khan Muhammad Mufazzal Saeed Kashif Naeem 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):277-283
The extraction behavior of nalidixic acid (HNA) in CH2Cl2 has been studied for various di- and trivalent metal ions such as Cu(II), Fe(II), Ni(II), Mn(II), Sb(II), Co(II), Sc(III),
Y(III), Nd(III) and Eu(III) from aqueous buffer solutions of pH 1–7 with 0.1 mol dm−3 nalidixic acid in dichloromethane. Separation factors of Sc(III) from these metals has shown that its clean separation is
possible at pH 3.4–4. The parameters affecting the extraction of Sc(III) were optimized. The composition of the extracted
adduct was determined by slope analysis method that came out to be Sc(NA)3. Extraction of Sc(III) was studied in the presence of various cations and anions. Among the anions studied only fluoride,
citrate and oxalate have significant interference whereas, Fe(III) has reduced the extraction to 53% that can be removed by
using ascorbic acid as reducing agent. The proposed extraction system proved good stability up to six extraction-stripping
stages for the extraction of Sc(III). 相似文献
6.
Summary Stability constants of copper (II) and nickel (II) oxalates have been determined by paper electrophoresis. Oxalic acid (0.005
mol dm−3) was added to the background electrolyte: 0.1 mol dm−3 HClO4. The proportions of HC2O
4
−
and C2O
4
2−
were varied by changing the pH of the electrolyte, these anions yielding the complex ions MHC2O
4
+
and M(C2O4)
2
2−
, average values of the stability constants for which are 102.4 and 107.6 respectively for Cu(II), and 102.3 and 106.5 for Ni(II) (μ=0.1,30°). 相似文献
7.
Agnieszka Nosal-Wiercińska Gra?yna Dalmata 《Monatshefte für Chemie / Chemical Monthly》2009,8(1):1421-1424
Abstract
This article proposes a simple and fast method of In(III) determination in the presence of Cd(II) and Pb(II). The catalytic activity of N-methylthiourea was used in the In(III) electroreduction, which also had a slight effect on the electroreduction process of Cd(II) and Pb(II). By applying square wave voltammetry it was possible to determine 3 × 10−7 mol dm−3 In(III) in the presence of 5 × 10−5 mol dm−3 Cd(II) and 1 × 10−4 mol dm−3 Pb(II) in 5 mol dm−3 NaClO4 at pH 2. The calibration curve for In(III) was linear from 3 × 10−7 to 5 × 10−4 mol dm−3. The relative standard deviation for In(III) determination was about 3.0%. 相似文献8.
Alaa Eldin M. Abdel-Hady 《Transition Metal Chemistry》2008,33(7):873-878
A kinetic study of the oxidation of [Co(H2L)(H2O)2]2+ (H2L = N,N-bis (salicylaldehyde-1,2-diaminoethane) Schiff base) by periodate in aqueous solution was performed over pH (2.3–3.4) range,
(0.1–0.5) mol dm−3 ionic strength and temperatures 20–35 °C for a range of periodate and complex concentrations. The reaction rate showed a
first-order dependence on both reactants and increased with pH over the range studied. The effects of Cu(II) and Fe(II) on
the reaction rate were investigated over the (1.0–9.0) × 10−5 mol dm−3 range. The reaction was inhibited as the concentration of Cu(II) increased, and it was independent on Fe(II) concentrations
over the ranges studied. An inner-sphere mechanism is proposed for the oxidation pathways of both the protonated and deprotonated
CoII complex species. 相似文献
9.
Two single-step extraction procedures validated by BCR, extraction with 0.43 mol dm−3 acetic acid and 0.05 mol dm−3 EDTA, are used for assessing bioavailable species of Pb and Cd in soils. After an extensive study of interferences of humic
substances and using standard additions procedures, the extractable contents of Pb and Cd have been determined by DPASV directly
in soil extracts with a good reproducibility (RSD varied from 1.0 to 7.9 %). Pb(II) and Cd(II) were released from complex
in EDTA extracts by pH adjustment to 1 with 1 mol dm−3 HCl. The results were compared with those obtained with atomic absorption spectrometry and indicated reasonable agreement
of both methods. Exchangeable forms represented 0.2 to 3.3 % and 13.0 to 63.6 % of total content of Pb and Cd in soils, respectively.
EDTA extraction released from soils 7.9 to 29.9 % and 33.5 to 59.6 % of total content of Pb and Cd, respectively. 相似文献
10.
Joaquin F. Perez-Benito 《Monatshefte für Chemie / Chemical Monthly》2001,132(12):1477-1492
Summary. The catalytic action of Cu(II) on the decomposition of H2O2 in near-neutrality aqueous solutions is activated by halide ions. The activation energies amount to 113±7 (parent reaction)
and 69.9±1.4 (chloride-activated reaction) kJ · mol−1. Free-radical chain mechanisms are proposed for both the parent reaction and the halide-activated reaction. The catalyst
activation caused by halide ions is explained in terms of coordination of halide ligands by both Cu(II) and Cu(I), the coordination
causing a higher stabilization of Cu(I) than of Cu(II). At low concentrations, Br− causes an inhibition of the Cu(II)/H2O2 reaction. This is explained in terms of an increase of the rate of termination of the chain reaction due to the scavenging
effect of OH radicals caused by Br−.
Received March 27, 2001. Accepted (revised) May 25, 2001. 相似文献
11.
A novel heterospin one-dimensional (1-D) chain complex containing both Cu(II) and nitroxide radical ligands, {[Cu(tcph)(H2O)4][Cu(tcph)(NIT3Py)2]·2H2O}
n
(1) (H2tcph = tetrachloro-phthalic acid, NIT3Py = 2-(3′-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide), has been synthesized
and structurally characterized. The structure consists of neutral chains of copper(II) ions bridged by tcph and coordinated
alternatively by nitroxide radicals as spin branches and solvated water as co-ligand. The magnetic data were fitted using
an approximate theoretical model based on population analysis to obtain the coupling parameter values of J
Cu2-Rad = 22.4 cm−1 and J′Cu1-Cu2 = −2.4 cm−1, indicating the intramolecular ferromagnetic interaction between Cu(II) and NIT3Py and weak antiferromagnetic interaction
between Cu1 and Cu2 linked by tcph. 相似文献
12.
V. A. Demin A. I. Kamenev N. P. Zveryak V. I. Zarembo 《Journal of Analytical Chemistry》2010,65(1):87-90
The behavior of Cd(II), Pb(II), Cu(II), and I− in the aqueous solutions of sodium chloride is studied by stripping voltammetry. A new version of using an indicator electrode
from carbon glass ceramics modified with mercury for the consecutive stripping determination of Cd(II), Pb(II), Cu(II), and
iodide is proposed. The mercury-graphite electrode was formed in the solution of a supporting electrolyte based on NH4Cl, HCl, 0.05 M potassium tetraoxalate (KH3C4O3 · 2H2O), and 5 × 10−5 M mercury(II). At first, Cd(II), Pb(II), Cu(II), and then iodide were determined by anodic-cathodic stripping voltammetry
after adding a sample solution (table salt, 10–100 mg/mL NaCl). 相似文献
13.
The complexation of As(V) in aqueous solutions in the presence of iron(III) was investigated spectrophotometrically with both
variable and constant ionic strengths. The determined thermodynamic and stoichiometric formation constants of the FeHAsO4+ species are log10∘β = 9.21± 0.01 and log10Iβ (1.0mol⋅dm−3 NaClO4) = 7.78 ± 0.01, respectively. The numerical treatment of the obtained spectral data was performed with the SPECA program. The analysis required the consideration
of the hydrolysis of Fe(III) and the protonation of As(V) in the pH range studied. No significant hydrolysis was observed
because of the low pH values (pH < 2.5) involved. The stabilities of the solid Fe(III) arsenates was established by solubility
experiments. All of the solubility experiments were performed in aqueous NaClO4 solutions at constant ionic strength (1.0mol⋅dm−3) and at 25∘C. The experimental data were consistent with FeAsO4⋅2H2O being the solid phase (log10 ∘ Kso = −24.30± 0.08). The corresponding thermodynamic constants were computed by means of the Modified Bromley's Methodology (MBM)
that describes the variation of the activity coefficients of all of the ions involved in the complexation and precipitation
equilibria with the medium and ionic strength. Finally, the solid phase obtained in this work was also characterized by FT-IR
and FT-Raman spectroscopies, and the hydration of the solid iron arsenate was confirmed by X-ray diffraction data. 相似文献
14.
In this work, 1,10-phenanthroline was used as a complexing agent for the separation and preconcentration of Cd(II), Co(II), Ni(II), Cu(II) and Pb(II) on activated carbon. The metals were adsorbed on activated carbon by two methods: static (1) and dynamic (2). The optimal condition for separation and quantitative preconcentration of metal ions with activated carbon for the proposed methods was for (1) in the static methods in the pH range 7-9. The desorption was found quantitative with 8 mol dm−3 HNO3 for Cd(II) (92.6%), Co(II) (95.6%), Pb(II) (91.0%), and with 3 mol dm−3 HNO3 for Cd(II) (95.4%), Pb(II) (100.2%). The preconcentration factor was 100 with R.S.D. values between 1.0 and 2.9%. For (2), the dynamic method (SPE), the pH range for the quantitative sorption was 7-9. The desorption was found quantitative with 8 mol dm−3 HNO3 for Cd(II) (100.6%), Pb(II) (94.4%), and reasonably high recovery for Co(II) (83%), Cu(II) (88%). The optimum flow rate of metal ions solution for quantitative sorption of metals with 1,10-phenanthroline was 1-2 cm3 min−1 whereas for desorption it was 1 cm3 min−1. The preconcentration factor was 50 for all the ions of the metals with R.S.D. values between 2.9 and 9.8%.The samples of the activated carbon with the adsorbed trace metals can be determined by ICP-OES after mineralization by means of a high-pressure microwave mineralizer. The proposed method provides recovery for Cd (100.8%), Co (97.2%), Cu (94.6%), Ni (99.6%) and Pb (100.0%) with R.S.D. values between 1.2 and 3.2%.The preconcentration procedure showed a linear calibration curve within the concentration range 0.1-1.5 μg cm−3. The limits of detection values (defined as “blank + 3s” where s is standard deviation of the blank determination) are 5.8, 70.8, 6.7, 24.6, and 10.8 μg dm−3 for Cd(II), Pb(II), Co(II), Ni(II) and Cu(II), respectively, and corresponding limit of quantification (blank + 10s) values were 13.5, 151.3, 20.0, 58.9 and 33.2 μg dm−3, respectively.As a result, these simple methods were applied for the determination of the above-mentioned metals in reference materials and in samples of plant material. 相似文献
15.
T. V. Maltseva E. O. Kudelko V. N. Belyakov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2336-2339
It was studied the equilibrium adsorption and adsorption kinetics of Cu(II), Cd(II), Pb(II), and Cr(VI) by composite hydroxides
formed by Me
x
O
y
· nH2O and Me0.4–0.7Al0.6–0.3O
y
· nH2O, where Me = Zr, Sn and Ti. It was estimated the values of the diffusion coefficients of adsorbed ions Cu(II) and Cr(VI)
from kinetic values. It was established that the estimated diffusion coefficients of adsorbed ions Cu(II) are in the range
0.4 × 10−12–2.5 × 10−12 m2/s for individual hydroxides and 1.2 × 10−12–2.8 × 10−12 m2/s for double hydroxides. The obtained values of diffusion coefficients Cr (VI) for double hydroxides are 0.1 × 10−10–0.4 × 10−10 m2/s. 相似文献
16.
Brahim Hacht 《Journal of solution chemistry》2008,37(2):155-163
Potentiometric titrations of aqueous acetic acid alone and in the presence of Ca(II) or Mg(II) ions have been carried out
under physiological conditions at the temperature 37 °C and ionic strength 0.15 mol⋅dm−3 (NaCl) at different ligand-to-metal ratios. Changes in pH were monitored with a glass electrode calibrated daily in terms
of the hydrogen ion concentrations. Titration data within the pH range 2.5 to 6.6 were analyzed to determine stability constants
using the SUPERQUAD program. Different combinations of complexes were considered during the calculation procedure for both
systems, but evidence was found only for mononuclear ML and ML2 species. Speciation calculations based on the corresponding constants were then used to simulate the species’ distributions. 相似文献
17.
Azizollah Nezhadali 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):307-308
The selective polymer membrane transport of Cu(II) from an aqueous solution containing seven metal cations, Co(II), Ni(II), Cu(II), Zn(II), Ag(II), Cd(II) and Pb(II), was studied .The source phase contained equimolar concentrations of the above-mentioned cations, with the source and receiving phases being buffered at pH 4.9 and 3.0, respectively. Cu(II) ion transport occurred (J=2.82 × 10−7 mol/h at 25 °C) from the aqueous source phase across the polymer membrane (derived from cellulose triacetate) containing ligand (I) as the ionophore, into the aqueous receiving phase. Clear transport selectivity for Cu(II) was observed. 相似文献
18.
Abstract
The characterization of an optical sensor membrane is described for the determination of tin (II) based on the immobilization of dithizone on a triacetylcellulose membrane. The membrane responds to tin (II) ions by changing color reversibly from green to red in buffer solution at pH 6 and wavelength 611 nm. This optode has a linear range of 0.3–6.33 μg cm−3 (2.52–53.32 μmol dm−3) of Sn2+ ions with a limit of detection of 0.15 μg cm−3 (1.26 μmol dm−3). The response time of the optode was about 8–10 min depending on the concentration of Sn2+ ions. The selectivity of the optode to tin (II) ions at pH 6 was good. The sensor can be readily regenerated by exposure with EDTA solution. The color is fully reversible, and the optical sensor could be fully regenerated. Experimental results showed that the optode could be used as an effective tool in analyzing the tin content in canned foods. 相似文献19.
Asela Chandrasoma Amer Al Abdel Hamid Alice E. Bruce Mitchell R.M. Bruce Carl. P. Tripp 《Analytica chimica acta》2012
A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the “proof of principle” of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5 μg of Hg(II) cm−2. In a 1 L sample and a 1 cm2 Si wafer, this translates to a detection limit of 5 ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions. 相似文献
20.
D. Kostova 《Russian Journal of Inorganic Chemistry》2011,56(6):968-974
The system manganese(VII)-methyl violet(MV)-water-chloroform has been studied. The composition of the complex is established
as MV: MnO4−=1:1. The molar absorptivity of the complex is (2.67 ± 0.09) × 104 l mol−1 cm−1 at 300 nm, limit of detection is 0.027 μg ml−1 and the system obeys Beer’s law in the range 0.22–1.6 μg ml−1 Mn(VII). The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase was determined.
The influence of foreign ions on the accuracy of the results is investigated. Extraction investigations of the system discussed
were carried out. A new rapid, selective, simple and sensitive extractive-spectrophotometric method for the determination
of trace amounts of manganese(VII) in plants, soils and steels were developed. 相似文献