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1.
Ag(Au) bimetallic core–shell nanoparticles were prepared by a new seed growth method. Ascorbic acid was used to reduce the complex of HAuCl 4 and hexadecyltrimethylammoniumbromide (CTAB). This resulted in the forming of colorless Au(I) (AuCl 2−). It was used as the growth solution to prepare these bimetallic core–shell nanoparticles. These nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed these nanoparticles exhibited core–shell shape and there was large amount of Ag in the shell. These nanoparticles could be produced in a few minutes without violent stirring and the method was easy and convenient compared with others. The effect of amount of AuCl 2− on the shape of nanoparticles was also studied. Many small gold nanoparticles were formed on the surface of bimetallic core–shell nanoparticles in the presence of excess AuCl 2−. The mechanisms were also proposed to explain the process of colloidal preparation. 相似文献
2.
Temperature dependence studies of adsorption of sulfuric acid species on Pt(1 1 1) and Au(1 1 1) electrodes were carried out using in situ infrared reflection absorption spectroscopy. A temperature-dependent shift of the interconversion potential between HSO 4−/H 3O + and H 2SO 4 on a Pt(111) electrode was observed. A temperature-dependent frequency shift of the absorption bands of HSO 4− was also observed on both Pt(1 1 1) and Au(1 1 1) electrodes in the potential region where a √3×√7 structure evolved. Modelling experiments in ultrahigh vacuum revealed that ordering of the overlayer water molecules played an important role in the frequency of the absorption bands of HSO 4−. 相似文献
3.
Inorganic anions are almost always determined by capillary electrophoresis (CE) at an alkaline pH, so the analytes will be fully ionized. However, a long-chain quaternary ammonium salt usually must be added as a flow modifier to the carrier electrolyte to reverse the direction of the electroosmotic flow. By working at a sufficiently acidic pH, the electroosmotic flow in fused-silica capillaries is virtually eliminated, and anions can be separated simply by differences in their electrophoretic mobilities. Excellent separations were obtained for AuCl 4− and the chloro complexes of platinum group elements in HCl solution at pH 2.0 to 2.4. No additional buffer or flow modifier was needed. This CE technique is an excellent way to follow slow hydrolytic reactions in which one or more of the chloride ligands is replaced by water. Sharp peaks and good separations were also obtained for MnO 4−, VO 3−, chromate, molybdate, ferrocyanide, ferricyanide and stable complex ions such as chromium oxalate (CrO 33−). 相似文献
4.
The paper reports results of a study on the specific adsorption of F −, Cl −, Br −, I −, ClO 3−, BrO 3−, IO 3− and IO 4− on hydrous γ-Al 2O 3. The isotherms of the anion adsorption and the adsorption dependencies on pH and the ionic strength of the solution have been determined under the equilibrium conditions. According to the degree of affinity to γ-Al 2O 3, the anions can be ordered as: I −3− −−3−3−4−−. It has been established that the sorption of IO4− and F− involves the formation of surface complexes in the inner co-ordination sphere, whereas that of Cl−, Br−, I−, ClO3−, BrO3− and IO3− takes place through formation of ion pair complexes in the outer co-ordination sphere. In the dynamic system, the exchange isoplanes and elution curves have been determined for selected anions on columns filled with Al2O3. It has been shown that γ-Al2O3 can be used for isolation and concentration of IO3− from natural waters in order to decrease the limit of the ions determination to 2 μg l−1. Using differential pulse voltammetry (DPV), after isolation and concentration on γ-Al2O3, the content of iodates has been determined in mineral, marine and tap water doped with these ions. 相似文献
5.
Composite diazotization-coupling reagents containing sulfanilamide (SAM), sulfapyridine (SP) or sulfathiazole (ST) as the diazotizable aromatic amines and sodium 1-naphthol-4-sulfonate (NS) as the coupling agent using column preconcentration on naphthalene-tetradecyldimethylbenzylammonium(TDBA)-iodide adsorbent have been used for the spectrometric determination of trace nitrate and nitrite in soil and water samples. Nitrite ion reacts with SAM in the pH range 2.0–5.0, SP in the pH range 2.0–2.5 and ST in the pH range 2.0–3.3 in HCl medium to form water-soluble colourless diazonium cations. These cations were coupled with NS in the pH range 9.0–12.0 for the SAM system, 9.6–12.0 for the SP system and 8.5–12.0 for the ST system to be retained on naphthalene-TDBA-I material packed in a column. The solid mass is dissolved from the column with 5 ml of dimethylformamide and the absorbance is measured spectrometerically at 543 nm for SAM-NS, 533 nm for SP-NS and 535 nm for ST-NS. Nitrate is reduced to nitrite by a copper-coated cadmium reductor column and the nitrite is then treated with the diazotization-coupling reagent by column preconcentration. The absorbance due to the sum of nitrate and nitrite is measured and nitrate is determined by difference. The calibration graph was linear over the range 2–40 ng NO 2−-N ml −1 and 1.5–30 ng NO 3−-N ml −1 in aqueous samples for the SAM and ST systems and 2–48 ng NO 2−-N ml −1 and 1.5–36 ng NO 3−-N ml −1 in aqueous samples for the SP system, respectively. The sensitivity, accuracy and precision of the systems decreased in the order STSAMSP. The detection limits were 1.4 ng NO 2−-N ml −1 and 1.1 ng NO 3−-N ml −1 for SAM, 1.6 ng NO 2−-N ml −1 and 1.2 ng NO 3−-N ml −1 for SP, and 1.0 ng NO 2−-N ml −1 and 0.75 ng NO 3−-N ml −1 for ST, respectively. The preconcentration factors are 8, 5 and 6 for SAM-NS, SP-NS and ST-NS, respectively. Interferences from various foreign ions have been studied and the methods have been applied to the determination of ng ml −1 levels of nitrite and nitrate in soil and water samples. The mean recovery was 95–102% for all three systems. 相似文献
6.
This study describes a new ion chromatography method using a low-capacity anion exchange column with amperometric and absorbance detection for rapid and simultaneous determination of Br − and NO 3− in contaminated waters where one of these ions is present in excess compared to other. The use of two detectors overcomes the problem of baseline separation for Br − and NO 3− for accurate quantification, which was commonly encountered when using a low-capacity anion exchange column and suppressed conductivity detection mode. The method achieved accurate quantification of these two ions without requirement of baseline separation. The accuracy of 2.8% for NO 3− was determined using a quality control sample obtained from UN GEMS/Water PE Study No. 6. The detection limits for Br − and NO 3− were 20 and 6 μg l −1 (25 μl sample), respectively. Linearity of these two ions was over three orders of magnitude with a correlation coefficient >0.998. The influence of potential interfering ions was also studied followed by the determination of Br − and NO 3− in seawater, unsaturated zone water, soil extract and groundwater. 相似文献
7.
A new concept of an amplified electrochemical detection of carbohydrates is proposed, where carbohydrates are oxidized by periodate ion (IO 4−) in acidic solutions to yield iodate ion (IO 3−) which would be electrochemically reduced into iodide ion (I −) under suitable conditions. This scenario allows highly sensitive detection of carbohydrates, for example, as 30 electrons per aldohexose molecule. Our cyclic voltammetric study revealed that IO 3− is reduced at much lower overpotentials than IO 4− at gold, platinum and carbon-based electrodes despite the fact that the standard redox potential of the IO 3−/I − couple is more negative than that of the IO 4−/I − couple. In the electrochemical reduction of IO 3−, I − is considered to function as a mediator. Stable flow-through detection of IO 3− in the presence of IO 4− was realized at glassy carbon electrodes. This method was coupled with the IO 4− oxidation of carbohydrates and the experimental conditions were partially optimized on a flow injection system. The IO 4− oxidation-coupled electrochemical detection of carbohydrates was applied to ligand-exchange high-performance liquid chromatography in a post-column mode. Sub-nanomole order of carbohydrates were successfully detected on this system. 相似文献
8.
Bismuth as BiCl 4− and BH 4− ware successively retained in a column (150 mm × 4 mm, length × i.d.) packed with Amberlite IRA-410 (strong anion-exchange resin). This was followed by passage of an injected slug of hydrochloric acid resulting in bismuthine generation (BiH 3). BiH 3 was stripped from the eluent solution by the addition of a nitrogen flow and the bulk phases were separated in a gas–liquid separator. Finally, bismutine was atomized in a quartz tube for the subsequent detection of bismuth by atomic absorption spectrometry. Different halide complexes of bismuth (namely, BiBr 4−, BiI 4− and BiCl 4−) were tested for its pre-concentration, being the chloride complexes which produced the best results. Therefore, a concentration of 0.3 mol l −1 of HCl was added to the samples and calibration solutions. A linear response was obtained between the detection limit (3 σ) of 0.225 and 80 μg l −1. The R.S.D.% ( n = 10) for a solution containing 50 μg l −1 of Bi was 0.85%. The tolerance of the system to interferences was evaluated by investigating the effect of the following ions: Cu 2+, Co 2+, Ni 2+, Fe 3+, Cd 2+, Pb 2+, Hg 2+, Zn 2+, and Mg 2+. The most severe depression was caused by Hg 2+, which at 60 mg l −1 caused a 5% depression on the signal. For the other cations, concentrations between 1000 and 10,000 mg l −1 could be tolerated. The system was applied to the determination of Bi in urine of patients under therapy with bismuth subcitrate. The recovery of spikes of 5 and 50 μg l −1 of Bi added to the samples prior to digestion with HNO 3 and H 2O 2 was in satisfactory ranges from 95.0 to 101.0%. The concentrations of bismuth found in six selected samples using this procedure were in good agreement with those obtained by an alternative technique (ETAAS). Finally, the concentration of Bi determined in urine before and after 3 days of treatment were 1.94 ± 1.26 and 9.02 ± 5.82 μg l −1, respectively. 相似文献
10.
This paper analyzes the comparison between the performances and morphologies of the PMMA gel and composite electrolyte membrane with nanosized MgO particles. These polymer electrolytes were studied in detailed using XRD, DSC, SEM and AC impedance analysis. The conductivity enhancement has been attributed to the addition of ceramic filler that yields a significant increase of surface to volume ratio related to the decrease in glass transition temperature values in the composite polymer electrolyte. Good interfacial stability at the electrode/electrolyte interface resulted on account of the improved ion dissociation by ceramic filler and a rise in the room temperature conductivity (8.14 × 10 −3 S cm −1) due to the iono-covalent or Lewis acid–base bonds to the ions and ether oxygen base groups was also observed. Further enhancement of conductivity has been observed on MgO surface, as Lewis-acidic sites interact with both PMMA and ClO 4− ions. The percentage of swelling was found to increase with increasing soaking periods upto 12 h. Beyond that soaking period, it was found that there was a negligible increase in the % of swelling. 相似文献
11.
A novel spectrophotometric reaction system was developed for the determination of nitrite as well as nitrate in water samples, and was applied to a flow-injection analysis (FIA). The spectrophotometric flow-injection system coupled with a copperised cadmium reductor column was proposed. The detection was based on the nitrosation reaction between nitrite ion and phloroglucinol (1,3,5-trihydroxybenzene), a commercially available phenolic compound. Sample injected into a carrier stream was split into two streams at the Y-shaped connector. One of the streams merged directly and reacted with the reagent stream: nitrite ion in the samples was detected. The other stream was passed through the copperised cadmium reductor column, where the reduction of nitrate to nitrite occurred, and the sample zone was then mixed with the reagent stream and passed through the detector: the sum of nitrate and nitrite was detected. The optimised conditions allow a linear calibration range of 0.03–0.30 μg NO 2−-N ml −1 and 0.10–1.00 μg NO 3−-N ml −1. The detection limits for nitrite and nitrate, defined as three times the standard deviation of measured blanks are 2.9 ng NO 2−-N ml −1 and 2.3 ng NO 3−-N ml −1, respectively. Up to 20 samples can be analyzed per hour with a relative standard deviation of less than 1.5%. The proposed method could be applied successfully to the simultaneous determination of nitrite and nitrate in water samples. 相似文献
12.
Organic-rich natural waters from peat bogs in continental (Switzerland) and maritime (Shetland Islands, Scotland) areas were analysed for Cl −, NO 2−, Br −, NO 3−, HPO 42−, SO 42− and oxalate using ion chromatography. These anions can be determined simultaneously in the surface and pore water samples from the continental bogs using a 250-μl injection loop. Using this loop, the detection limits were ca. 5 ng/g for the monovalent anions and SO 42− and 10 ng/g for HPO 42− and oxalate. An organics-removal cartridge (Dionex OnGuard P) was used to remove humic materials. These cartridges did not significantly affect the measured concentrations of anions in blind standards. Analyses of deionized water treated with these cartridges are not significantly different from those for untreated deionized water. For the maritime bogs, the relatively high concentrations of Cl − (more than 100μ/g in many samples) and SO 42− (up to 50 μg/g) require two separate determinations for complete analyses. A 10-μl injection loop was used to determine Cl −, Br − and SO 42−. A 250-μl injection loop was used to measure NO 2−, NO 3−, HPO 42− and oxalate. In each instance a Dionex OnGuard P cartridge was used to remove humic materials. In addition, a chloride-removal cartridge (Dionex OnGuard AG) was used to remove Cl − when the larger injection loop was used. This cartridge has no significant effect on the measurement of HPO 4-2− at concentrations of 20 ng/g. In each of the bog water chromatograms there were usually a number of unknown peaks. These are probably due mainly to organic anions. 相似文献
13.
A novel thin-layer amperometric detector (TLAD) based on chemically modified ring-disc electrode and its application for simultaneous measurements of nitric oxide (NO) and nitrite (NO 2−) in rat brain were demonstrated in this work. The ring-disc electrode was simultaneously sensitive to nitric oxide (NO) and nitrite (NO 2−) by modifying its inner disc with electropolymerized film of cobalt(II) tetraaminophthalocyanine (polyCoTAPc)/Nafion and its outer ring with poly(vinylpyridine) (PVP), respectively. The ring-disc electrode was used to constitute a novel TLAD in radial flow cell for simultaneous measurements of NO and NO 2− in rat brain combined with techniques of high performance liquid chromatography (HPLC) and in vivo microdialysis. It was found that the basal concentration of NO in the caudate nucleus of rat brain is lower than 1.0×10 −7 mol l −1, NO 2− concentration is 5.0×10 −7 mol l −1 and NO exists in brain maybe mainly in the form of its decomposed product. 相似文献
14.
A rapid potentiometric flow injection technique for the simultaneous determination of oxychlorine species such as ClO 3−–ClO 2− and ClO 3−–HClO has been developed, using both a redox electrode detector and a Fe(III)–Fe(II) potential buffer solution containing chloride. The analytical method is based on the detection of a large transient potential change of the redox electrode due to chlorine generated via the reaction of the oxychlorine species with chloride in the potential buffer solution. The sensitivities to HClO and ClO 2− obtained by the transient potential change were enhanced 700–800-fold over that using an equilibrium potential. The detection limit of the present method for HClO and ClO 2− is as low as 5×10 −8 M with use of a 5×10 −4 M Fe(III)–1×10 −3 M Fe(II) buffer containing 0.3 M KCl and 0.5 M H 2SO 4. On the other hand, sensitivity to ClO 3− was low when a potential buffer solution containing 0.5 M H 2SO 4 was used, but could be increased largely by increasing the acidity of the potential buffer. The detection limit for ClO 3− was 2×10 −6 M with the use of a 5×10 −4 M Fe(III)–1×10 −3 M Fe(II) buffer containing 0.3 M KCl and 9 M H 2SO 4. By utilizing the difference in reactivity of oxychlorine species with chloride in the potential buffer, a simultaneous determination method for a mixed solution of ClO 3−–ClO 2− or ClO 3−–HClO was designed to detect, in a timely manner, a transient potential change with the use of two streams of potential buffers which contain different concentrations of sulfuric acid. Analytical concentration ranges of oxychlorine species were 2×10 −5–2×10 −4 M for ClO 3−, and 1×10 −6–1×10 −5 M for HClO and ClO 2−. The reproducibility of the present method was in the range 1.5–2.3%. The reaction mechanism for the transient potential change used in the present method is also discussed, based on the results of batchwise experiments. The simultaneous determination method was applied to the determination of oxychlorine species in a tap water sample, and was found to provide an analytical result for HClO, which was in good agreement with that obtained by the o-tolidine method and to provide a good recovery for ClO 3− added to the sample. 相似文献
15.
A new method has been developed for ion-interaction chromatography with suppressed conductivity detection and a new graphitized carbon packing, which is sintered from carbonic material at a high temperature. Combinations of various eluting agents, tetrabutylammonium hydroxide (TBA) and acetonitrile have been investigated to optimize the separation of eight common anions (F −, Cl −, NO 2−, Br −, NO 3−, SO 42−, HPO 42− and I −). Calibration curves were linear from 0.5 to 10 μg/ml for F −, from 1.0 to 20 μg/ml for Cl −, NO 2− and NO 3−, from 2.5 to 50 μg/ml for Br − and SO 42− and from 5.0 to 100 μg/ml for HPO 42− and I − with a correlation coefficient ( r) of 0.999 or better. The relative standard deviations (R.S.D.s) of peak areas were between 0.2 and 0.9% for 10 repeated measurements. The application of this newly developed method was demonstrated by the determination of chloride, bromide and sulfate in pharmaceutical compounds using the direct injection method. The analytical results were within ±2% (relative) of the theoretical value, and thus in good agreement with the theoretical value for each sample. 相似文献
16.
The infrared spectra of solid samples of C 4H 7K and C 4D 7K have been investigated in the 4000 to 30 cm −1 range. A complete assignment of intramolecular fundamentals of C 4H 7− and C 4D 7− ions and of potassium-allyl vibrations is proposed and the intramolecular force constants are calculated. The C(CH 2) 32− anion has been identified spectroscopically. Structures of C 3H 5−, C 4H 7− and C(CH 3) 32− are discussed and compared with those optimised by the MINDO/3 method. 相似文献
17.
Thin layers of gold (700 Å) were deposited on manufactured alumina pourous supports to yield nanopores with openings of <7 nm. A self-assembled monolayer (SAM) of alkyl thiols was then attached to provide a hydrophobic support for trialkyl phosphine oxide-based metal ion carriers. The resulting gated membranes provided a barrier to ions including H +, and Ca 2+, NO 3−, and CH 3COO −. When an aqueous feed solution of 4.2 mM uranyl nitrate and 1 M lithium nitrate pH 4, and a receiving solution of 1 M sodium acetate pH 5.5 were used 100% of the metal was transported across the membrane by facilitated transport via the phosphate or phosphine oxide carrier. The thin gates transported metal ions as neutral nitrate complexes with fluxes high enough to be limited by the alumina support. The flux rates of 200,000 metal ions per pore per second are only a factor of 5 below that observed for the potassium channel. High selectivity of U over Eu is observed until the [U] is <0.84 mM in the feed solution, despite the fact the Eu actually transports faster when U is not present. This work demonstrates that selectivity can be added without impeding transport by using thin selective layers. 相似文献
18.
Homocystine was for the first time, chemically linked to a highly cross-linked agarose support (Novarose) to be employed as a chelating adsorbent for preconcentration and AAS determination of nickel in table salt and baking soda. Nickel is quantitatively adsorbed on a small column packed with 0.25 ml of the adsorbent, in a pH range of 5.5–6.5 and simply eluted with 5 ml of a 1 mol l −1 hydrochloric acid solution. A factorial design was used for optimization of the effects of five different variables on the recovery of nickel. The results indicated that the factors of flow rate and column length, and the interactions between pH and sample volume are significant. In the optimized conditions, the column could tolerate salt concentrations up to 0.5 mol l−1 and sample volumes beyond 500 ml. Matrix ions of Mg2+ and Ca2+, with a concentration of 200 mg l−1, and potentially interfering ions of Cd2+, Cu2+, Zn2+ and Mn2+, with a concentration of 10 mg l−1, did not have significant effect on the analyte's signal. Preconcentration factors up to 100 and a detection limit of 0.49 μg l−1, corresponding to an enrichment volume of 500 ml, were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked nickel in table salt and baking soda solutions resulted in quantitative recoveries. Direct ETAAS determination of nickel in the same samples was not possible because of a high background observed. 相似文献
19.
The three cyanocuprate(I) complexes, Cu(CN) 2−, Cu(CN) 32−, and Cu(CN) 43−, photoeject electrons with high efficiency when excited in aqueous solution by 266 nm laser pulses of 7 ns duration with quantum yields of 0.37±0.06, 0.224±0.021, and 0.240±0.005, for Cu(CN) 2− (at 2 M ionic strength), Cu(CN) 32−, and Cu(CN) 43− (both measured at 1 M ionic strength). Along with hydrated electrons, two transient intermediates, absorbing at 460 and 340 nm, respectively, form consecutively after excitation through bimolecular reactions with ground-state Cu(I) in solutions of Cu(CN) 2−, and Cu(CN) 32−, but not in Cu(CN) 43−. All photoprocesses are essentially monophotonic. A mechanism is proposed that suggests the formation of a dinuclear excited-state complex such as an excimer. 相似文献
20.
The complex equilibria between HCrO 4− and Cl − ions has been studied spectrophotometrically at a constant ionic strength of 3.0 mol dm −3 and the data have been analyzed both graphically and numerically by means of the program LETAGROP-SPEFO (L. G. Sillen and B. Warnquist, Arkiv. kemi. 1968, 31, 377). The experimental results can be explained on the basis of the following reaction: HCrO 4−+H ++Cl − = CrO 3Cl −+H 2O (log β 11 = 1.37±0.08). Molar absorptivities of HCrO 4− and CrO 3Cl − were also reported. 相似文献
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