共查询到20条相似文献,搜索用时 25 毫秒
1.
P. Kannan 《Analytica chimica acta》2010,663(2):158-407
We are reporting the highly sensitive determination of hydroxylamine (HA) using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) capped fused spherical gold nanoparticles (AuNPs) modified Au electrode. The fused TAA-AuNPs were immobilized on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film, which was pre-assembled on Au electrode. The immobilization of fused TAA-AuNPs on MPTS sol-gel film was confirmed by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The AFM image showed that the AuNPs retained the fused spherical morphology after immobilized on sol-gel film. The fused TAA-AuNPs on MPTS modified Au electrode were used for the determination of HA in phosphate buffer (PB) solution (pH = 7.2). When compared to bare Au electrode, the fused AuNPs modified electrode not only shifted the oxidation potential of HA towards less positive potential but also enhanced its oxidation peak current. Further, the oxidation of HA was highly stable at fused AuNPs modified electrode. Using amperometric method, determination of 17.5 nM HA was achieved for the first time. Further, the current response of HA increases linearly while increasing its concentration from 17.5 nM to 22 mM and a detection limit was found to be 0.39 nM (S/N = 3). The present modified electrode was also successfully used for the determination of 17.5 nM HA in the presence of 200-fold excess of common interferents such as urea, NO2−, NH4+, oxalate, Mn2+, Na+, K+, Mg2+, Ca2+, Ba2+ and Cu2+. The practical application of the present modified electrode was demonstrated by measuring the concentration of HA in ground water samples. 相似文献
2.
A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 × 10−6 to 4.0 × 10−2) with a super Nernstian slope of 28.5 (±0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe3+ ion in comparison to some hard and soft metals such as Fe2+, Cd2+, Cu2+, Al3+ and Ca2+. It has a response time of <15 s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe3+ in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions. 相似文献
3.
5,11,17,23‐Tetra‐tert‐butyl‐25,26,27,28‐tetrakis(diphenylphosphinoylmethoxy)calix[4]arene ( 1 )has been used for the preparation of a graphite coated thorium ion‐selective electrode (Th4+‐ISE). The plasticized PVC membrane containing 30% PVC, 58% ortho‐nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 8% ionophore was directly coated on a graphite rod. This sensor gave good Nernstian responses with a slope of 15.5 ± 0.1 mV/decade over a concentration range of 1 × 10?5 ?1 × 10?3 M of thorium ions with a limit of detection of 7.9 × 10?6 M. The dynamic response time of the electrode to achieve a steady potential was found to be about 15 seconds. The potential of the prepared sensor was independent of the pH variation in the range 2.3–4.0. The selectivity relative to several mono‐, di‐ and tri‐valent metal ions, i.e. Li+, Na+, K+, Ag+, NH4+, Sr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, La3+, Sm3+, Dy3+, Er3+ and Y3+ was examined. This electrode can be used for 6 months without any considerable divergences in the potential response. The sensor was successfully used as an indicator electrode for the potentiometric titration of a thorium solution using a standard solution of EDTA. 相似文献
4.
Emilia Konował Anna Modrzejewska-Sikorska Anna Maria Kopaczewska Bożena Karbowska 《Electroanalysis》2021,33(9):2071-2077
A method of producing nanosilver by using lignosulfonic acid derivative and a new method of the obtained AgNPs-LS electrode material for developing a chemically modified GCE/AgNPs-LS/Hg electrode is presented. The data demonstrate that the modified electrode shows enhanced performance in determining Tl+ ions in comparison to unmodified electrode GCE. The stripping anodic peak current of thallium characterized in linearity over its concentration range from 1.22 ⋅ 10−8 to 1.15 ⋅ 10−7 mol dm−3, with detection limit 4.6 ⋅ 10−9 mol dm−3. It is assumed that the novel AgNPs-LS/Hg2+ complex is suitable for preparing functionalized nanostructured material and can be used as an electrochemical sensing platform for heavy metals. 相似文献
5.
A method is described for determining 10-5–10-4M fluoride in a variety of solutions potentiometrically with a fluoridc-specific electrode, by a standard addition method. Any change of ionic strength or the nature of the solution that might alter activity coefficients or junction potentials is minimized. The relationship between potential and fluoride concentration thus follows the Nernst equation, and the unknown concentration can be calculated. Experimental data are given for solutions of sodium choride, sodium nitrate, acidified sodium silicate and sodium hydroxide, lithium chloride, and phosphoric acid. Metal ions (e.g., Al3+, UO22+, Fe3+, Th4+) that interfere by forming complexes with fluoride can be precomplexed with phosphoric acid. The relative error is estimated at 10%, and the relative standard deviation is less than 5% over the concentration range 10-5–10-4M fluoride. 相似文献
6.
J. Devynck B. Trémillon M. Sloim H. Ménard 《Journal of Electroanalytical Chemistry》1977,78(2):355-369
In molten potassium hydrogenodifluoride (KHF2) fully ionized into K+ and HF2?, at 250°C, the HF2? ion is slightly dissociated according to the equilibrium: HF2?HF+F?. This is a solvent acid base equilibrium, HF being the strongest acid and F? the strongest base in this system. By means of a voltammetric study we showed that the hydrogen electrode may be used as an acidity indicator electrode in the whole acidity range of the melt. By analysis of the equilibrium potential variation in acidic and in basic media, the HF2? dissociation constant (melt autoprotolysis constant): KD = {HF} {F?} was determined The experimental value: KD=10?2.05 mol2 kg?2 is compared with a calculated one, issued from thermodynamic data. Results obtained with other electrodes (LaF3 monocrystal electrode and copper electrode) were discussed and compared with those obtained with the hydrogen electrode. 相似文献
7.
Metal-ion complexation of 7-benzylimidazo[1,2-a]pyrazin-3(7H)-one derivative (2) with Li+, Mg2+, Ca2+, Ba2+, Sc3+, and La3+ in acetonitrile resulted in successive modulations of its UV/vis absorption and fluorescence spectroscopic properties. This result indicates that 2 can be used as a colorimetric and fluorometric sensor of the Lewis acidity of a metal ion in aprotic solutions. The hypothesis that the metal-ion complex has a O10(imidazopyrazinone)-metal ion bond was supported by X-ray crystallographic analysis and quantum chemical calculations for a Li+ complex of 7-methylimidazo[1,2-a]pyrazin-3(7H)-one derivative (1). 相似文献
8.
《Journal of Electroanalytical Chemistry》1984,160(1-2):185-198
The electrochemical oxidation of 2,4,6-tribromoaniline in aqueous sulphuric acid solutions, at different concentrations, and in aqueous 60% perchloric acid solution, at a platinum electrode, has been studied by rotating disc electrode and cyclic voltammetry. An irreversible first oxidation process, controlled by diffusion is observed, in perchloric acid and in sulphuric acid concentration <12.5 M. At higher sulphuric acid concentration, this process is kinetically controlled. The electroactive species is the protonated form Ar−N+H3, which is bielectronically oxidized to [Ar−NH3]3+ cation. Deprotonation of this cation can produce two different species, Ar−N2+ H2 (I) and Ar+−N+H3 (II). In the latter case (II), the deprotonation occurs from the benzene ring. Hydrolysis of (I) gives 3,5-dibromo-1,2,4-trihydroxybenzene, which is further oxidized to 3,5-dibromo-2-hydroxy-2,5-cyclohexadien-1,4-dione. This charge-transfer equilibrium explains an additional redox pair observed for the first process in cyclic voltammograms. An irreversible second oxidation process corresponding to an initial bielectronic oxidation of (II), in both sulphuric acid at concentration >9.0 M and perchloric acid solutions, is observed. Generally, this second process is kinetically controlled. The rate-determining step of both processes is attributed to the initial charge transfer for the electrode reaction under diffusion control or to an adsorption process, depending on the medium used. 相似文献
9.
《中国化学快报》2020,31(10):2835-2838
In this paper, a novel mesoporous silica gel evenly doped by Prussian blue nanoparticles (PBMSG) was successfully synthesized by using N,N-dimethylamide as template with a large Barrett-Emmett-Teller (BET) surface area of 505 m2/g and an average pore size of 2.9 nm. The static adsorption experiments showed that the equilibration time of PBMSG for Cs+ was about 30 min. The adsorption isotherm of PBMSG for Cs+ accorded with Langmuir model and the theoretical maximum adsorption capacity was 80.0 ± 2.9 mg/g. When the initial concentration of Cs+ was 1.00 mg/L, the adsorption partition coefficient Kd could reach 3.5 × 104 mL/g After adsorption, Cs+ could be eluted by dilute hydrochloric acid (pH 2) with an efficiency of 89.8%, while no K+, Fe3+, Fe2+ was eluted. PBMSG exhibited good selectivity toward Cs+ and Rb+. In the presence of high concentration of K+, the selective adsorption of PBMSG could change the mass ratio of K+, Rb+ and Cs+ from 96.63:0.83:1.00–1.12:0.73:1.00. The separation of Cs+ and Rb+ from K+ with similar concentration (100 mg/g) was realized by column experiment. This indicated that PBMSG was suitable for rapid recovery of low concentration of rubidium and cesium from complex matrixes, such as wastewater and salt lake brine, etc. 相似文献
10.
Silver(I)‐Selective PVC Membrane Potentiometric Sensor Based on a Recently Synthesized Calix[4]arene
《Electroanalysis》2006,18(10):1019-1027
A new PVC membrane potentiometric sensor for Ag(I) ion based on a recently synthesized calix[4]arene compound of 5,11,17,23‐tetra‐tert‐butyl‐25,27‐dihydroxy‐calix[4]arene‐thiacrown‐4 is developed. The electrode exhibits a Nernstian response for Ag(I) ions over a wide concentration range (1.0×10?2?1.0×10?6 M) with a slope of 53.8±1.6 mV per decade. It has a relatively fast response time (5–10 s) and can be used for at least 2 months without any considerable divergence in potentials. The proposed electrode shows high selectivity towards Ag+ ions over Pb2+, Cd2+, Co2+, Zn2+, Cu2+, Ni2+, Sr2+, Mg2+, Ca2+, Li+, K+, Na+, NH4+ ions and can be used in a pH range of 2–6. Only interference of Hg2+ is found. It is successfully used as an indicator electrode in potentiometric titration of a mixture of chloride, bromide and iodide ions. 相似文献
11.
The determination of the voltammetric curves, I=f(E), of maleic acid and of a basic titrant in N,N-dimethylformamide using 3 electrodes allowed interpretation of the polarovoltric titration curves of the neutralization of this acid by sodium methylate and tetrabutylammonium hydroxide. The different variations of the potential between 2 polarized platinum electrodes observed in such a neutralization reaction were identified and a notation was developed so that the origin of the observed potential variations could be established. The signal EcH+→S, which is related to the initial acidity, is given by the cathode and corresponds to a jump from the potential of the H+ reduction curves to that of the solvent reduction curves. The signal EAS→OH- characteristic of the second acidity, is given by the anode and is related to a jump from the potential of the solvent oxidation curves to that of the titrant oxidation curves.The effect of the use of unsymmetrical polarized electrodes (a rotating filament electrode and a large-surface, stationary electrode) on the shape of the titration curve was also examined: a rotating cathode gave rise to a curve resembling an inverted U, whereas a rotating anode gave rise to a curve resembling a deformed M. 相似文献
12.
Richard D. Goodin John C. Gilbert Allen J. Bard 《Journal of Electroanalytical Chemistry》1975,59(2):163-168
The acidity level and the fluoride ion activity are evaluated in anhydrous HF and in water+HF mixtures of HF content higher than 70% by means of R(H) and R(F) functions. For both functions, the potentials of the ferrocene/ferricinium or perylene+/perylene2+ systems are used as reference potentials. A hydrogen electrode is used for acidity level evaluation and it is shown that the R(H) function decreases (acidity increases) when HF content increases in the mixture; the value of R(H) is ?15.5 for anhydrous hydrogen fluoride (+KF 0.1 M). A lanthanum trifluoride monocrystal electrode is built and used for F? activity evaluations and it is shown that the R(F) function increases (activity of fluoride ion decreases) when HF content increases, up to R(F)=13.6 for basic anhydrous HF (KF 0.1 M solution). 相似文献
13.
Solvent extraction of a mixture of PbII, MnII, FeIII, CoII, NiII and CdII in aqueous perchlorate medium by a phosphorylated hexahomotrioxacalix[3]arene (calix‐3) in dichloromethane shows a significant selectivity towards lead ions. The ligand can also be incorporated into a membrane to provide a new lead ion‐selective electrode (PbII‐ISE). A plasticized PVC membrane containing 30% PVC, 53.5% ortho‐nitrophenyloctylether (NPOE), 4.5% sodium tetraphenylborate (NaTPB) and 12% ionophore was directly coated on a graphite rod. This sensor gave a good Nernstian response of 29.7 ± 0.7 mV decade?1 over a concentration range of 1 × 10?8 – 1 × 10?4 M of lead ions, independent of pH in the range 3‐7, with a detection limit of 0.4 × 10?8 M. The dynamic response time of the electrode to achieve a steady potential was very fast and found to be less than 7 s. The selectivity relative to Ag+, NH4+, Li+, Na+, K+, Ca2+, Sr2+, Ba2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Fe3+, La3+, Sm3+, Dy3+, Er3+, Y3+ and Th4+ was examined. The electrode exhibits adequate stability with good reproducibility (with a slope of 29.6 ± 1.5 mV for 8 weeks). The characteristics of the sensor are compared with those of a tetraphosphorylated calix[4]arene (calix‐4) based PbII‐ISE, reported recently. The electrode was successfully used as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for lead ion measurements in various synthetic samples was also investigated. 相似文献
14.
The catalytic effects of metal ions on the anodic oxidation of ascorbic acid on a Pt electrode in 1 M HClO4 were studied by linear sweep voltammetry. The anodic peak due to a two-electron oxidation of ascorbic acid shifts to the negative potential side on the addition of Bi3+. This indicates the accelerating effect of Bi3+ on the oxidation of ascorbic acid. The presence of other metal ions, such as Pb2+, Hg2+, Tl+, Ag+ and Sb3+, also exerts similar effects. These metal ions were adsorbed on a Pt electrode at underpotentials and the adsorbed metals (denoted as Mad) still remain on the electrode surface until the electrode potential goes up to and beyond the peak potential of the oxidation of ascorbic acid. On the other hand, metal ions forming no adsorbed layer on Pt, such as Co2+, Zn2+, Fe3+ and Ni2+, exhibit no catalytic effect. These facts suggest that the presence of a Mad on Pt is essential for the promotion of the anodic oxidation of ascorbic acid. However, there is a difference in the catalytic action among the Mad, for example, Cuad, Cdad, Inad, Snad and Moad display no catalytic action.The catalytic activity depends on the degree of surface coverage by the Mad. The maximal effect of the Mad is attained in the submonolayer region. The effects of metal ions were discussed on the basis that the Mad plays its major role in the removal of the adsorbed ascorbic acid occupying active sites on the electrode surface, and provides effective sites for the activation of adjacent water molecules. Furthermore, from the 13C NMR spectra for the oxidation products, the adsorbed water on the Mad appears to function by promoting the subsequent hydration steps, following the electron-transfer step of ascorbic acid. 相似文献
15.
Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (Pr3+, Eu3+, Ho3+, Tm3+)
Maria Michela Salvatore Antonietta Siciliano Alessia Staropoli Francesco Vinale Rosario Nicoletti Marina DellaGreca Marco Guida Francesco Salvatore Mauro Iuliano Anna Andolfi Gaetano De Tommaso 《Molecules (Basel, Switzerland)》2022,27(19)
Rare-earth elements (REEs) are in all respect a class of new contaminants that may have toxic effects on organisms and microorganisms and information on their interactions with natural ligands should be of value to predict and control their diffusion in natural environments. In the current study, we investigate interactions of tripositive cations of praseodymium, europium, holmium, and thulium with harzianic acid (H2L), a secondary metabolite produced by selected strains of fungi belonging to the Trichoderma genus. We applied the same techniques and workflow previously employed in an analogous study concerning lanthanum, neodymium, samarium, and gadolinium tripositive cations. Therefore, in the current study, HPLC-ESI-HRMS experiments, circular dichroism (CD), and UV-Vis spectrophotometric absorption data, as well as accurate pH measurements, were applied to characterize bonding interactions between harzianic acid and Pr3+, Eu3+, Ho3+, and Tm3+ cations. Problems connected to the low solubility of harzianic acid in water were overcome by employing a 0.1 M NaClO4/(CH3OH + H2O 50/50 w/w) mixed solvent. For Pr3+, Ho3+, and Tm3+, only the mono complexes PrL+, HoL+, and TmL+ were detected and their formation constant determined. Eu3+ forms almost exclusively the bis complex for which the corresponding formation constant is reported; under our experimental conditions, the mono complex EuL+ is irrelevant. Combining the results of the present and previous studies, a picture of interactions of harzianic acid with rare-earth cations extending over 8 of the 17 REEs can be composed. In order to complement chemical information with toxicological information, a battery of bioassays was applied to evaluate the effects of praseodymium, europium, holmium, and thulium tripositive cations on a suite of bioindicators including Aliivibrio fischeri (Gram-negative bacterium), Raphidocelis subcapitata (green alga), and Daphnia magna (microcrustacean), and median effective concentration (EC50) values of Pr3+, Eu3+, Ho3+, and Tm3+ for the tested species were assessed. 相似文献
16.
A new binuclear complex of copper2+, [LCu2+(CH3COO)2Cu2+L](CH3COO)2 where L is N,N-bis(phthalimide)ethylenediamine, was synthesised and characterised. The complex ion [LCu2+ (CH3COO)2Cu2+L]2+ was encapsulated into ZSM-5 zeolite and used to modify the surface of the glassy carbon electrode. This modified electrode, in a phosphate buffer solution at pH 7.0, exhibited an oxidation potential for dopamine (DA) and ascorbic acid (AA) at electrode potentials of 0.230 V and ?0.090 V vs. Ag/AgCl respectively, a separation of 0.320 V. The electro-oxidation of DA or AA on the modified electrode is independent of each other. No interference was observed from Na+, K+, Cl?, SO 4 2? , Mg2+, Ca2+, Zn2+, Fe2+, and glucose. The detection limits obtained were 2.91 × 10?7 M for DA and 3.5 × 10?7 M for AA. 相似文献
17.
Dimethyl-4,4-dimethoxy-5,6,5′,6′-dimethylene dioxy biphenyl-2,2-dicarboxylate (DDB) liver drug is used as a novel ionophore in plasticized poly (vinyl chloride) (PVC) matrix membrane sensors for barium ions. Optimum performance characteristics are displayed by membrane sensor incorporating DDB ionophore, potassium tetrakis(4-chlorophenyl)borate as lipophilic salt, and o-nitrophenyloctyl ether as plasticizer. The sensor exhibits a linear response over the concentration range 10−1-10−5 mol l−1 BaCl2 with a Nernstian slope of 30 mV per decade and high selectivity towards Ba2+ with respect to Li+, Na+, K+, Rb+, NH4+, Mg2+, Ca2+, Sr2+, Mn2+, Co2+, Ni2+, Cd2+, Al3+, La3+, and Ce3+ ions. The sensor response is stable over a wide pH range (4-9) and the lifetime is about 2 months. The proposed sensor is successfully applied to the determination of Ba2+contents of some rocks. 相似文献
18.
Summary The estimation of bismuth by the reagent Bismuthiol II is studied critically. The effect of acidity, reagent concentration and interfering ions are given in detail. The maximum acidity that may be tolerated for the complete precipitation of bismuth is 0.3 N in nitric acid, 0.5 N in hydrochloric acid and 1N in sulphuric acid. Higher acidity than 0.1 N decomposes the reagent present in excess. In 0.1 N nitric acid bismuth has been separated from a number of ions like Al3+, Cr3+, Th4+, rare earths, Zr4+, Ti4+, UO2
2+, Be2+, Mn2+, Co2+, Ni2+, Mg, alkalis and alkaline earths, SO4
2–, Cl–, C2O4
2–- and from Fe2+ and Ce3+ in 0.1 N hydrochloric acid. In presence of a citrate or a tartrate it can be separated from As3+, Ce4+, MoO4
2–- and WO4
2–-at pH 1.5 to 2.5. When Hg2+, Pb2+, Pd2+, Cd2+, Cu2+, Ag+ and Tl+ are present they are first precipitated by the reagent at pH 6 to 8 in presence of a citrate or a tratrate and the bismuth is estimated gravimetrically in the acidified filtrate. Ions as F– and PO4
3– that form insoluble compounds with bismuth, Sb3+ and Sn2+ that form less soluble compounds with the reagent and Fe3+, VO3
–, CrO4
2–, AsO4
3– that act as oxidising agents, interfere. 相似文献
19.
Y.-Z. Wei B. Fang T. Arai M. Kumagai 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):409-415
Electrochemical reduction of U(VI) in nitric acid-hydrazine solution is greatly influenced by the concentration of nitric
acid. In low acidity nitric acid solution such as 0.1M (M=mol/dm3) HNO3, U(VI) was firstly reduced to U(V) and then partially reduced to U(IV). In high acidity nitric acid solution, e.g., 3-6M
HNO3, an electrode process of two-electron transfer was involved in the reduction of U(VI). A higher U(IV) yield could be achieved
in nitric acid solution with higher concentration. Hydrazine was very effective in suppressing the reduction of concentrated
nitric acid, and the optimal concentration of hydrazine added was 0.075 to 0.15M in 6M HNO3
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Two electrodes modified with either nickel or cupric hexacyanoferrate films were evaluated and compared as sensors for nonelectroactive cations in a flow-injection system. Both gave responses for group 1A and ammonium ions, but only the electrode modified with cupric hexacyanoferrate was sufficiently stable for use in flowing solutions. This electrode responded to K+, NH, Rb+, and Cs+ ions rather selectively. Within this group, the selectivity could be controlled from general to almost specific toward Cs+ by the potential at which the electrode was poised. The electrode was compatible with a mobile phase of dilute nitric acid commonly used in ion chromatography, and chromatographic detection limits of 2 × 10−7 M and linear responses over two decades were obtained. The electrode was applied to the ion chromatographic analysis of K+ and NH in urine and K+ in blood serum samples. 相似文献