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1.
A water-in-oil type emulsion containing oxine has been used for the discrimination of copper(II) ions and copper-humic complexes
in aqueous solutions. A toluene solution containing oxine and nonionic surfactant (Span-80) was vigorously mixed with 1 mol/L
HCl by ultrasonic irradiation. The resulting emulsion was added to water and dispersed by stirring as numerous small globules.
Copper(II) ions were quantitatively permeated across the oil layer and incorporated in the tiny droplets of HCl, whereas copper-humic
complexes remained in the sample solution. After collecting the dispersed emulsion globules, they were destroyed by heating
to segregate the aqueous (HCl) and organic (toluene) phases. The copper in the aqueous phase was determined by graphite-furnace
atomic absorption spectrometry (GFAAS). The analytical results agreed with those obtained by the adsorption method, where
negatively charged humic complexes were selectively collected on a macroreticular anion exchanger Sephadex A-25 column. The
conventional liquid-liquid extraction did not offer a chemical speciation because copper(II) ions and humic complexes were
simultaneously extracted into the organic phase. The proposed emulsion method was successfully applied to the analysis of
river water samples.
Received: 14 April 1998 / Revised: 22 July 1998 / Accepted: 27 July 1998 相似文献
2.
An oxine-impregnated emulsion was prepared by dissolving 100 mg of oxine and 0.3 ml of non-ionic surfactant (Span-80) in 10 ml of toluene and mixing with 3 ml of 1 mol l(-1) hydrochloric acid by sonication (20 kHz). The water-in-oil emulsion was injected into 50 ml of water sample (containing iron(III) at the ppb level, pH 4-7) and dispersed by stirring for 10 min as numerous small globules (0.1-0.5 mm in diameter). The iron diffused through the toluene layer into the small droplets of hydrochloric acid. The emulsion was separated by flotation and heated to segregate the aqueous (hydrochloric acid) and organic (toluene) phases. The iron in the aqueous phase was determined by graphite-furnace atomic absorption spectrometry (GFAAS). Hydrated iron(III) oxide having particle sizes of larger than 1 mum did not penetrate into the emulsion. Other iron species which were not incorporated into the emulsion include humic complexes and hybrid particles of hydrated iron(III) oxide and humic substances. This discrimination can be attributed to the surfactant layer at the oil-water interfaces and gentle stirring of the solution. The conventional liquid-liquid extraction, however, did not offer such a selectivity, because all iron(III) species were simultaneously extracted into the organic phase with vigorous shaking. The unique property of the emulsion method has been applied to the separation and determination of inorganic dissolved iron species in river water. 相似文献
3.
An oil type emulsion containing tiny encapsulated droplets of hydrochloric acid has been used for the concentration of traces of copper(II) ions in water. Milligram quantities of oxine and a non-ionic surfactant (Span-80) were dissolved in 5-10 ml of chloroform and mixed vigorously with 3 ml of 1 mol/l hydrochloric acid by ultrasonic irradiation. The resulting water-in-oil type emulsion was gradually added to 50-500 ml of water sample and dispersed by stirring as numerous small globules (0.1 to 0.5 mm in diameter). The copper diffused through the chloroform layer into the small droplets of hydrochloric acid, which occurred quantitatively in the sample of pH 3-10. After separating the emulsion by sedimentation, it was demulsified by heating to segregate the aqueous and organic phases. The copper in the aqueous phase was successfully determined by GFAAS. The emulsion method allows to perform both extraction and back-extraction more easily and rapidly than the conventional liquid-liquid extraction method. 相似文献
4.
A new redox-driven type of emulsion liquid membrane separation is described. Milligram amounts of copper(II) in 0.2 M hydrochloric acid were reduced to copper(I) in the presence of ascorbic acid (1 M≡1 mol l−1). The copper solution was emulsified with a (1+4) mixture of toluene and n-heptane using Span-80 (sorbitan monooleate) as an emusifier. The resulting water-in-oil emulsion was dispersed in 0.2 M hydrochloric acid containing hydrogen peroxide and neocuproine (2,9-dimethyl-1,10-phenanthroline) by stirring for 10 min. The copper in the internal aqueous phase was selectively transported to the external one, leaving other heavy metals (e.g., Mn, Co, Ni, Cd and Pb) in the internal aqueous phase. After collecting the dispersed emulsion globules, they were demulsified by heating and the metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry (GFAAS). The selective transport of copper offered the multielement separation of trace heavy metals from a copper matrix, allowing the GFAAS determination of impurities at the 0.01% level in copper metal. 相似文献
5.
A water-in-oil (w/o) emulsion containing Kelex-100 (7-dodecenyl-8-quinolinol) and Span-80 (sorbitan monooleate, non-ionic surfactant) was ultrasonically prepared from 1.0 mol l−1 hydrochloric acid and a (1 + 3) mixture of toluene and n-heptane. The resulting emulsion was gradually injected into water sample and dispersed as numerous tiny globules (0.01-0.1 mm in diameter). Dissolved inorganic species (free metal species) of heavy metals (e.g., Fe, Co, Cu, Cd, and Pb) were selectively transported through the oil layer into the internal aqueous phase of the emulsion, leaving other species, such as humic complexes and suspended particles (larger than 1 μm), in the sample solution. After collecting the dispersed emulsion globules, they were demulsified and the heavy metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry. The emulsion-based separation method allowed the selective collection of free metal species with a high concentration factor of 100, whereas the conventional solvent extraction did not offer such discrimination. This unique property of the emulsion method was successfully applied to the selective determination of free species of heavy metals in fresh water samples. 相似文献
6.
Separation of traces of heavy metals from an iron matrix by use of an emulsion liquid membrane 总被引:3,自引:0,他引:3
An emulsion liquid membrane method has been developed for separating traces of heavy metals from an iron matrix. A 1.0-mL volume of aqueous iron(III) solution (pH 2.0) was emulsified with a mixture of 0.6 mL toluene, 2.4 mL n -heptane, and 80 mg sorbitan monooleate (Span-80). The resulting water-in-oil type emulsion was gradually injected into 25 mL of 1.5 mol L–1 hydrochloric acid solution containing 30 mmol L–1 8-quinolinol and 1.0 mol L–1 of ammonium sulfate and was dispersed as numerous tiny globules by stirring for 40 min. More than 90% of the iron(III) diffused through the oil layer to the external hydrochloric acid solution with the aid of complexation with 8-quinolinol, whereas trace heavy metals, e.g. Cr(III), Mn(II), Co(II), Ni(II), Cu(II), and Pb(II), remained quantitatively in the internal aqueous phase. After collecting the dispersed emulsion globules, they were demulsified and trace metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry. Owing to sufficient removal of the iron matrix trace metal impurities in high-purity iron were successfully determined without interference, as was confirmed by analysis of certified reference materials. 相似文献
7.
A water-in-oil type emulsion containing 8-quinolinol has been used for the concentration of traces of heavy metals from seawater prior to their determinations by graphite-furnace atomic absorption spectrometry. The emulsion used was prepared by dissolving 40 mg of 8-quinolinol and 60 mg of sorbitan monooleate (Span-80) in 3.0 ml of toluene and vigorously mixing with 0.70 ml of aqueous hydrochloric acid solution (1.5 mol l−1) by ultrasonic irradiation. The resulting emulsion was gradually injected into 100 ml of sample solution (pH 8.5) and dispersed by stirring as numerous tiny globules. Four heavy metals (Co, Ni, Cu, and Cd) in the sample solution were quantitatively transported through the organic layer into the acidic aqueous droplets encapsulated in the emulsion. After collecting the dispersed emulsion globules, they were demulsified by heating and the heavy metals in the segregated aqueous phase were determined by atomic absorption spectrometry. Owing to the highly efficient concentration (100-fold), these heavy metals at sub-ng ml−1 levels in seawater were determined with satisfactory accuracy and precision, being confirmed with certified reference samples. 相似文献
8.
Yasuaki Okamoto Yoshitaka Nomura Hiderou Nakamura Kazuyuki Iwamaru Terufumi Fujiwara Takahiro Kumamaru 《Microchemical Journal》2000,65(3):66
A high preconcentration method by liquid–liquid extraction using liquid surfactant membranes was developed. The water-in-oil (w/o) emulsion containing dilute hydrochloric acid, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (PC-88A), liquid paraffin, and kerosene was used for the extraction. In a resulting volume of 1000 cm3 of an aqueous sample solution (pH 5.0) containing less than 1 mg of each metal ion, 2 cm3 of w/o emulsion droplets coated with sorbitan monooleate were dispersed. The analyte metal ions in the outer bulk aqueous phase were extracted into the organic phase to form a complex with PC-88A and successively back-extracted into the inner aqueous phase. The analytes in the resulting inner aqueous phase were determined subsequently by graphite furnace atomic absorption spectrometry applied as a detector. By this procedure, concentration factors of 570, 820, 750, 970, 860, and 880 were achieved for chromium(III), manganese(II), cobalt(II), nickel(II), copper(II), and cadmium(II), respectively, and also the respective detection limits (3σ) of 0.4, 20, 1.2, 18, 18, and 0.7 pg cm−3 were obtained. 相似文献
9.
《Analytica chimica acta》1970,50(3):465-473
Absorption spectra of cobalt-oxine complexes-extractedinto chloroform indicate that two cobalt(II) and one cobalt(III) complexes can be extracted depending on pH and the initial concentrations of oxine in the organic phase or cobalt(II) ion in the aqueous phase. The oxidation state of cobalt in the complexes was determined by treatment of organic extracts with an 0.001 M EDTA solution at pH 4–5; cobalt(II) complexes were back-extracted, and the cobalt(III) complex was not. The equilibrium distribution ratios of cobalt(II) between aqueous perchlorate solutions and oxine solutions in chloroform were determined at 20°. A plot of logDco-log[HOx]o vs. pOx gave a single curve for different concentrations of oxine; it was concluded that cobalt(II) is extracted as CoOx2HOx. 相似文献
10.
Trace metal speciation measurements in waters by the liquid binding phase DGT device 总被引:3,自引:0,他引:3
The speciation measurements of trace metals by the diffusive gradients in thin-films technique (DGT) using a poly(4-styrenesulfonate) (PSS) aqueous solution as a binding phase and a cellulose dialysis membrane (CDM) as a diffusive layer, CDM-PSS DGT, were investigated and showed good agreement with computer modelling calculations. The diffusion coefficients of ethylenediaminetetraacetic acid (EDTA) complexes with Cd2+ and Cu2+ were measured and compared with those of the inorganic metal ions. CDM-PSS DGT device was tested for speciation measurement in sample solutions containing EDTA, tannic acid (TA), glucose (GL), dodecylbenzenesulfonic acid (DBS) and humic acid (HA) as complexing ligands forming organic complexes with varying stability constants. Lower percentages of DGT labile copper concentrations over total filterable copper concentrations obtained from the deployments in freshwater sites indicated that copper complexes with organic matter were basically not measured by the devices. 相似文献
11.
M. Wisniewski 《Journal of Radioanalytical and Nuclear Chemistry》2000,246(3):693-696
The commercial extractant Acorga CLX-50 and model individual di-2-ethylhexyl pyridine-3,5-dicarboxylate and 2-ethylhexyl pyridine-3-carboxylate in toluene were used for palladium(II) extraction from aqueous HCl solutions. The studies of extraction rate and equilibrium were carried out in systems containing palladium(II) ions in 3.0, 0.1, and 0.1M HCl in the presence of 0.5M sodium chloride and in 0.1M HCl in the presence of 0.1–6.0M lithium chloride and in 0.1M HCl in the presence 0.1–3.5M sodium nitrate. The examined extractants can efficiently extract palladium(II) from aqueous hydrochloric acid and nitrate solutions. The extraction is slow and equilibrium is obtained after 2 hours. The best extraction of palladium(II) is observed from 0.1M HCl solution in the presence of 3.5M sodium nitrate. A spontaneous transfer of palladium(II) to the toluene phase without any phase mixing is also observed. 相似文献
12.
A method for the determination of copper(II) complexes with humic acids was developed by batch operation with the cation exchanger sulphopropyl-Sephadex C-25 (C-25). The copper-binding ability (conditional stability constants and copper-complexing capacities) of humic acids which were extracted from peat in Hokkaido was evaluated. A solution containing copper(II) ions and humic acids was shaken with the C-25 exchanger. The copper-humic acid complexes remained in the supernatant and the uncomplexed free copper ion was retained on the C-25. The copper-humic acid complexes were determined by flame atomic absorption spectrometry. The copper-binding ability of nitrilotriacetic acid (NTA) as a model ligand was similarly determined with a Scatchard plot. The conditional stability constant obtained at pH 4.5 was in good agreement with the reported value. The copper-binding abilities of the humic acids from peat were estimated using a Scatchard plot adopting a two-site model. The functional groups in the humic acids which contribute to the complexation with copper were investigated by conductimetric and pH titration, and the relationship between the copper-binding sites and functional groups in the humic acids was investigated. 相似文献
13.
An influence of chloride ions, pH and humic substances concentration on complexation of cadmium(II)and copper(II) ions with
humic acids was studied by means of inversion-voltamperometry using the method of experimental design. Equations establishing
dependences of concentrations of humate complexes of cadmium(II) and copper(II) on concentrations of chloride and humic substances
and pH values too were derived. 相似文献
14.
《Electrochemistry communications》2001,3(6):306-311
The carbon ceramic electrodes impregnated with hydrophobic organic solvent (toluene, hexadecane, nitrobenzene) containing redox probe (decamethylferrocene) were prepared. The electrode material was obtained by sol–gel process. It consists of graphite powder homogeneously dispersed in hydrophobic silica matrix. After gelation and drying it was filled with organic liquid. The electrochemical properties of the electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Approximately symmetric cyclic voltammograms were obtained with these electrodes immersed in aqueous electrolyte solution. Their shape and current magnitude and position on the potential scale depends on the organic solvent and the salt present in aqueous phase. It has been concluded that the mechanism of the electrode process involves electron transfer between graphite particle and the redox probe in organic phase, followed by anion transfer from the aqueous phase. 相似文献
15.
The interaction of copper ions with peptides was investigated by electrospray mass spectrometry. Two electrospray micro-emitters were compared, the first one with a platinum electrode using a copper(II) electrolyte solution containing a peptide sample, and the second one with a sacrificial copper anode in a water/methanol solution containing only a peptide (i.e., angiotensin III, bradykinin, or Leu-enkephalin). The former yielded mainly Cu(2+) complexes either with histidine residues or with the peptide backbone (Cu(+) complexes can be also formed due to gas-phase reactions), whereas the latter can generate a mixture of both Cu(+) and Cu(2+) aqueous complexes that yield different complexation patterns. This study shows that electrospray emitters with soluble copper anodes enable the study of Cu(I)-peptide complexes in solution. 相似文献
16.
Metal ions (Cd, Cu, Pb, Co and Ni) in trace amounts were isolated from sample matrices and concentrated by extraction in a flow system. The sample flow was first mixed with buffer and reagent (carbamates) and the combined aqueous flow was next segmented with trichlorotrifluoroethane (Freon 113). The metal complexes were extracted into the organic phase in a 2-m long coil which was followed by a separator with a teflon membrane. The organic phase passed on to a second segmentor where an acidic, aqueous mercury(II) solution was added. Back-extraction to the aqueous solution took place in a 1-m long coil. The Freon was removed in a second membrane separator and the aqueous phase was collected and analyzed by graphite-furnace atomic absorption spectrometer. The enrichment factors were of the order of 15–20 and the recoveries were 90–100% from the sub-μg l?1 level up to 20–50 μg l?1. The recoveries decrease at concentrations above 50 μg l?1, presumably because of slow dissolution of precipitated complexes in the sample solutions. The observed recoveries for copper were generally somewhat lower, being in the range 80–90%. 相似文献
17.
Solvent extraction of tin(IV) from hydrochloric acid media was carried out with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in toluene. Tin(IV) was quantitatively extracted with 2.5x10(-2) M PC-88A in toluene from 0.1-0.3 M HCl when equilibrated for 5 min. Tin(IV) from the organic phase was stripped with 4 M HCl and determined spectrophotometrically by both the morin and pyrocatechol violet method. The nature of the extracted species was determined from the log-log plots. Various other diluents such as xylene, hexane and cyclohexane also gave quantitative extraction of tin. The metal loading capacity of the reagent was found to be 0-15 ppm of tin(IV). The extraction of tin(IV) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Tin(IV) was successfully separated from commonly associated metal ions such as antimony(III), bismuth(III), lead(II), thallium(I), copper(II), nickel(II), etc. The method was extended for determination of tin in real samples. 相似文献
18.
《Journal of membrane science》1986,26(2):129-142
A method has been developed to enhance the liquid membrane extraction of heavy metals such as cobalt, copper and nickel. The method consists of introducing anion ligands, such as acetate, to the aqueous solution containing metal ions. In the absence of a ligand in the aqueous phase, it takes about 15 min for a 80% cobalt recovery, while only 2 min are needed for a 95% recovery with the addition of 0.1 M acetate in the feed solution. The ligand effects on liquid membrane extraction are rationalized in terms of the labile nature of the ligand—metal complexes, the distribution coefficients of the metal ions, the interfacial and surface tensions, and by the nuclear magnetic r̀esonance (NMR) spectra of the metal—organic complexes. 相似文献
19.
Bolotin S. N. Frolov V. Yu. Panyushkin V. T. 《Russian Journal of General Chemistry》2004,74(2):219-221
Complex formation of copper(II) ions with the galactarate ion [Gala]2
- in aqueous solution was studied by means of potentiometric titration. Stability constants of the [CuGala] and [Cu(Gala)2]2
- complexes were determined. A complex compound was synthesized electrochemically and isolated from a DMSO solution containing a copper(II) salt and galactaric acid, and its composition was determined. The structure of the complex was determined by ESR. 相似文献
20.
《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,272(1-2):15-21
Using oil/water/oil-type emulsion liquid membranes, batch wise extraction experiments are carried out to separate toluene from a mixture of toluene and n-heptane. In the separation process using emulsion liquid membranes, the internal phase polydispersity affects mass transport of a solute because under steady operating conditions, internal droplet size and size distribution are proportional to the interfacial area. The present study aims to assess the polydispersity character of the internal droplets of emulsion globules. In this paper, the important variables affecting dispersed drop sizes as well as internal droplets mean diameter and size distribution of the emulsion globule, including impeller speed during emulsification, surfactant concentration, volume ratio of surfactant solution, carrier concentration and composition of feed phase are systematically investigated. 相似文献