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1.
In the present study newly developed potentiometric sensors for determination of zinc(II) are presented. The proposed potentiometric method was based on the fabrication of modified carbon paste (MCPE; electrode X) and modified gold nanoparticles-carbon paste (GNPs-CPE; electrode IX) sensors. A mercapto compound of 1,4-bis(5-mercaptopentyloxy)-benzene (BMPB) alone or self-assembled on gold nanoparticles was used as modifier to construct electrode (X) and electrode (IX) sensors, respectively. The prepared electrodes exhibit Nernstian slope of 29.93 ± 0.4 and 26.0 ± 1.02 mV decade−1 towards Zn(II) ion over a wide concentration range of 6.8 × 10−10 to 2.9 × 10−2 and 1.0 × 10−7 to 1.0 × 10−2 mol L−1 for electrode (IX) and electrode (X) sensors, respectively. The limit of detection of the electrode (IX) and electrode (X) sensors was found to be 6.8 × 10−10 and 1.0 × 10−7 mol L−1, respectively. The potentiometric response of the electrode (IX) and electrode (X) based on GNPs-BMPB and BMPB are independent of pH of test solution in the pH range of 2.5–8.1 and 3–7 with a response time of 6 and 8 s for electrode (IX) and electrode (X) sensors, respectively. The proposed sensors showed fairly good discriminating ability towards Zn(II) ion in comparison with many hard and soft metal ions. Finally, the proposed electrodes were successfully used as indicator electrodes in potentiometric titration of zinc ion with sodium tetraphenylborate (NaTPB) and in direct determination of Zn(II) ion in some water samples. The results obtained compared well with those obtained using atomic absorption spectrometry.  相似文献   

2.
The effect of halide ion concentration on the capacitor performance was considered during this study. Iodide anion has been selected as the most profitable halide taking into account its electrochemical properties and environmental impact. Several concentrations of NaI were tested (from 0.25 to 5 mol L?1 aqueous solutions) using as electrodes two commercial activated carbons and one KOH-activated carbon. Detailed electrochemical investigation by galvanostatic charging/discharging, cyclic voltammetry, and impedance spectroscopy confirmed the significant impact of iodide concentration on the supercapacitor behavior. The higher concentration of iodide affected especially the performance of positive electrode; increase of iodide concentration changed the potential range of positive electrode and its capacitance increased from 119 F g?1 for 0.25 mol L?1 NaI to 475 F g?1 for 2 mol L?1 NaI solution. The electrode capacitance measured in two-electrode system at current density of 2 A g?1 ranged from 198 F g?1 for 0.25 mol L?1 NaI to 272 F g?1 for 2 mol L?1 NaI solution (capacitance expressed as average of the positive and negative electrode capacitances). It has been proved that 2 mol L?1 alkali metal iodide solution is an optimal electrolyte for the capacitor based on KOH-activated carbon. High capacitance values and perfect stability (100 % retention) of such systems have been observed during long-term galvanostatic charging/discharging (15,000 cycles). In addition, satisfactory floating tests at extended voltage range (1.2 V) were performed.  相似文献   

3.
Novel cadmium selective coated graphite electrodes were prepared using three different ionophores N1, N2-dicyanoethyl-N1, N2-bis(pyridin-2-ylmethyl)benzene-1, 2-diamine [L1], N1, N2-dicyanoethyl-N1, N2-bis(thiophen-2-ylmethyl) benzene-1, 2-diamine [L2] and N1, N2-dicyanoethyl-N1, N2-bis(furan-2-ylmethyl)benzene-1, 2-diamine [L3], and their potentiometric characteristics were determined. Membranes having different compositions of poly(vinylchloride) (PVC), the plasticizer o-nitrophenyloctylether (o-NPOE), sodium tetraphenylborate (NaTPB) as an anionic additive and ionophores were coated onto the graphite surface. The potential response measurements showed that the best performance was exhibited by the electrodes with membranes having the composition L1: o-NPOE:NaTPB:PVC as 4:51:2.5:42.5 (wt.%), L2: o-NPOE:NaTPB:PVC as 3:52.5:1.5:43 (wt.%) and L3: o-NPOE:NaTPB:PVC as 7:49:3.5:40.5 (wt.%). These electrodes had the widest working concentration range, Nernstian slope and fast response times of 12 s, 7 s and 17 s for L1, L2 and L3, respectively. The selectivity studies showed that these electrodes have higher selectivity towards Cd2+ over a large number of cations and could tolerate up to 20 vol.% non-aqueous impurities. Furthermore, the electrodes generated constant potentials in the pH range 2.0–8.0, with a shelf life of approximately four to six weeks. The high selectivity of these electrodes permits their use in the detection of the Cd2+ content in some medicinal plants, soil and industrial wastewater samples. The electrodes could also be used as an indicator electrode in the potentiometric titration of Cd2+ with EDTA.  相似文献   

4.
This study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV–Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 × 10?9 mol L?1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water.  相似文献   

5.
Interactions of 134Cs(I), 152,154Eu(III), and 60Co(II) ions from HCl acid solutions with tungstocerate(IV) gel matrices, dried at 50°C, have been individually investigated by the batch equilibration method. The selectivity sequence was found to be in the order: Cs(I) >Eu(III) >Co(II). The breakthrough capacities of 12‐tungstocerate(IV) for Cs(I), Eu(III), and Co(II) were found to be 1.00, 0.55, and 0.26 mmol/g of the sorbent, respectively. In addition, a mixture of these radionuclides [6.20 × 10?3 M Cs(I), 3.53 × 10?3 M Eu(III), and 1.4 × 10?3 M Co(II)], in 150 ml of 0.02 M HCl solution was passed through 1‐g 12‐tungstocerate(IV) chromatographic column. Quantitative uptake of both 134Cs(I) and 152,154Eu(III) has been achieved, while only ?22% of 60Co(II) has been retained. Then, quantitative elution of the retained fraction of Co(II) was achieved with 14 ml of 0.1 M HCl acid solution leaving Eu(III) and Cs(I) strongly retained onto the column. Quantitative elutions of Eu(III) and Cs(I) were achieved by passing 20 ml of 0.3 M HCl and 16 ml of 2 M HCl acid solutions, respectively.  相似文献   

6.
A graphene quantum dots–gold nanoparticles–modified glassy carbon electrode was used to investigate the electrochemical behaviors of malachite green (MG). Cyclic voltammetry curves of MG at the modified electrode exhibited a pair of quasi-reversible adsorption-controlled redox peaks at 0.502 V (E pa) and 0.446 V (E pc) in a 0.05 mol L?1 H2SO4 solution. Under the optimal conditions, by using differential pulse voltammetry as the detection method, a linear relationship was obtained between the oxidation peak current and the MG concentration in the range of 4.0 × 10?7 to 1.0 × 10?5 mol L?1 with the detection limit as 1.0 × 10?7 mol L?1 (signal-to-noise ratio of 3). The modified electrode was applied in the determination of MG in fish samples, and the results were satisfactory with recoveries from 96.25 to 98.00 %. Furthermore, the modified electrode showed very good reproducibility and stability.  相似文献   

7.
A novel poly(crystal violet)/graphene-modified glassy carbon electrode (PCV/Gr/GCE) was fabricated for the simultaneous determination of Pb2+ and Cd2+. The electrochemical behavior of both species at the PCV/Gr/GCE was investigated employing cyclic voltammetry. In acetate buffer, the modified electrode showed an excellent electrocatalytical effect on the oxidation of both species and was further used for their determination. Under optimized analytical conditions, the oxidation peak currents of Pb2+ and Cd2+ obtained by differential pulse voltammetry in pH 4.6 acetate buffer showed a linear relationship with their concentrations in the ranges of 2.00 × 10?8–1.95 × 10?5 mol L?1 and 4.00 × 10?8–5.58 × 10?5 mol L?1, respectively. The developed method has excellent sensitivity, selectivity, reproducibility and has been successfully applied to the determination of Pb2+ and Cd2+ in water samples.  相似文献   

8.
A linear sweep anodic stripping voltammetric method using a carbon nanotube–gold nanoparticle-modified vibrating screen printed electrode for the determination of arsenic(III) is reported. The experiments were conducted with a 0.1 mol L?1 solution of H2SO4 in order to estimate the electrode area related to gold oxide formation. The results showed a clear reduction peak at approximately +0.85 V corresponding to the reduction of the gold surface oxide with a superficial area of 0.089 cm2. A vibrating motor was attached to the screen printed electrode to create a portable and autonomous system with enhanced mass transfer. The repeatability of the measurements was 2.4 % (n = 10) at the level of 0.5 mg L?1 of arsenic(III) under the best instrumental operating conditions. The peak current was linearly dependent on the arsenic(III) concentration, thus allowing the construction of a linear analytical curve in the range from 10 to 550 μg L?1 with the equation: ?Ip (μA) = 0.05 + 134.59 [As(III) (μg L?1)], R2 = 0.99. The obtained detection and quantification limits were 0.5 (3 SD) and 1.5 (10 SD) μg L?1, respectively, using 120 s as the deposition time. It was shown that Cu(II) does not interfere in the detection of As(III) using the proposed method.  相似文献   

9.
This paper describes the construction, evaluation, and application of an electrochemical sensor for the determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Satisfactory results were achieved for the simultaneous determination of DA and UA, it was verified that it is possible to detect AA in the presence of DA, but high concentrations of AA interfere in detection of DA. The sensor was constructed using the layer-by-layer (LbL) technique with the modification of the surface of indium tin oxide coated glass (ITO) substrate with nanostructured films comprising a 3-n-propylpyridinium silsesquioxane polymer (SiPy+Cl?) and nickel(II) tetrasulfophthalocyanine (NiTsPc). Using the square wave voltammetry technique (SWV), the LbL modified electrodes produced at different pHs (pH 2 and 8) were used to determine DA in the presence UA, and the electrochemical responses of the electrodes were compared. It was observed that the electrodes with the highest concentration of monomeric species showed the highest current intensity and the lowest peak potential for the DA and UA analytes in analysis of DA and UA, individually and simultaneously, with peak potential separation of 460 mV versus Ag/AgCl. Applying SWV, a linear dynamic range of 10–99 μmol L?1 and 100–900 μmol L?1 with detection limit of 16.8 μmol L?1 and 58.3 μmol L?1 was obtained for DA and UA, respectively. The method has good selectivity and sensitivity, and it was successfully applied to the simultaneous determination of DA and UA in spiked human urine sample.  相似文献   

10.
ABSTRACT

In this study, Zn(II) ion-imprinted polymer was prepared on the surface of vinyl silica particles and applied for detection of Zn(II) ions using differential pulse voltametry. The ion- imprinted polymer particles were prepared by free radical polymerization. The prepared particles were characterized by different morphological and elemental techniques. The ion-imprinted particles were used to fabricate the carbon paste electrode as a zinc ions sensor. The modified zinc sensor showed linear response in the concentration range 6.12 × 10?9 to 4.59 × 10?8 mol L?1. The limit of detection and limit of quantification of the electrode were 1.351 × 10?8 and 4.094 × 10?8 mol L?1, respectively.  相似文献   

11.
《分离科学与技术》2012,47(1):164-178
Abstract

The adsorption of different metal ions on acrylamidezirconium (IV) arsenate has been studied. The effect of surfactant concentration (Tween 80‐R and Tritron X‐100) on sorption of different metal ions acrylamidezirconium (IV) arsenate was explored. The effect of experimental parameters such as contact time, temperature, and pH on adsorption of Pb2+ions was studied. The promising feature of the material is its specificity for Pb2+ ions. A new PVC based Pb2+ ion‐selective electrode using acrylamidezirconium (IV) arsenate as electro‐active material has been fabricated. The electrode works well over a wide range of concentration 1×10?1 M–1×10?7 M with a Nerstian slope of 30±1 mV per decade. The sensor shows the short response time of 20 seconds and can operate in the pH range of 2–7. The sensor can be used for the period of over 4 months with out deviation in response characteristics. The electrode has been successfully used as an indicator electrode for potentiometric titration of Pb2+ ions in solution against EDTA solution.  相似文献   

12.
Abstract

Electro‐oxidation of Ce(III) to Ce(IV) in nitric acid media at different anode materials with high oxygen evolution overpotential was carried out. Ce(IV) nitrato complexes were adsorbed on a novel resin, based on porous silica beads with immobilized polystyrene/DVB copolymer, that was impregnated with tri‐n‐butyl phosphate (TBP). Under the studied conditions, Ce(IV) sorption increased with increasing nitric acid concentration (0.5–6 mol · dm?3). Oxidation of sorbent by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed and thoroughly evaluated. In spite of problems with TBP leakage (12%), column separation of pure Ce(IV) from Y(III) and La(III) was achieved in 6 mol · dm?3 HNO3 at 288 K. Ce(IV) breakthrough capacity was 0.48 mol · kg?1‐TBP. Column regeneration with 0.1 mol · dm?3 nitric acid yielded Ce solution with purity higher than 99.99 wt.% with respect to La and Y impurities.  相似文献   

13.
《分离科学与技术》2012,47(15):3465-3480
Abstract

Preparation of a high stable solvent impregnated resins (SIR) containing 1,4‐dihydroxyanthraquinone (quinizarin, QNZ) was proposed using Amberlite XAD‐16 beads. The SIR was applied for the separation of Cd(II), Cu(II), Ni(II), and Zn(II) in aqueous media prior to the determination by flame atomic absorption spectrometry (FAAS). The optimum conditions for batch mode extraction of the above metal ions were investigated and it was found that the sorption of these metal ions from a 1000‐ml aliquots of the solution on 1.5 g of the SIR can be carried out quantitatively at pH of 9.5 and an ionic strength of 0.01 mol dm?3. The sorbed metal ions were subsequently eluted with 10 ml 2 mol dm?3 HCl and the eluent was subjected to FAAS. Beer's law was obeyed in the range of 9×10?9 ?1×10?7 mol dm?3 for Cd(II) and Zn(II), and 9×10?8 ?1×10?6 mol dm?3 for Cu(II) and Ni(II) contents. Significant interference was not observed due to the various ions, which could be found in natural water samples. The practical applicability of the method was confirmed using a synthetic certificated reference material (CRM) and spiked natural water samples.  相似文献   

14.
This paper introduces the development a new chemically modified carbon paste electrode (CMCPE) for the determination of a cationic surfactant. The paste is based on alkyl dimethyl hydroxyethyl ammonium chloride (ADHACl) with phosphomolybdic acid as an ion‐exchanger (ADHA‐PM). The electrode exhibits a Nernstian slope of 59.1 ± 0.5 mV/decade for ADHA ions in the concentration range 1.0 × 10?6–1.0 × 10?3 M with the limit of detection of 8.2 × 10?7 M. The proposed electrode has a fast and stable response time of 5–8 s, a good reproducibility and it can be used in the pH range of 2.2–9.0. Selectivity coefficients, determined by a matched potential method and separate solution method, showed high selectivity for ADHA over a large number of inorganic cations and organic cations. These characteristics of the electrode enable it to be used successfully for determination of ADHA in shampoo and liquid detergents solutions by standard addition and the calibration curve methods. In addition, the modified electrode was applied as an indicator electrode in potentiometric titration and successfully used to determine ADHA in water samples with satisfactory results.  相似文献   

15.
《分离科学与技术》2012,47(16):2609-2624
ABSTRACT

SBA-15 mesoporous materials modified by sulfonic acid and sulfamic acid functionalities, abbreviated as SBA-15/SO3H and SBA-15/NHSO3H, were synthesized and applied for the removal–separation of Eu(III), Th(IV), and U(VI). SBA-15/NHSO3H showed an excellent selectivity toward U(VI), while SBA-15/SO3H was more efficient adsorbent for Eu(III) and Th(IV). It was found that in the presence of KNO3 (1 mol L?1), the separation of Eu(III)/Th(IV) from their mixtures is possible. The results of the sorption behavior indicated a high adsorption capacity toward U(VI) and Th(IV) ions (140.5 and 106.7 mg g?1, respectively) and ultrafast kinetics (15 min) in Eu(III) adsorption.  相似文献   

16.
In this work, an electrochemical β-nicotinamide adenine dinucleotide (NADH) sensor based on a carbon paste electrode modified with nickel oxide nanoparticles (NiONPs) was developed. The key highlights of this work are ease of preparation of the NiONPs-modified carbon paste electrode (NiONPs/MCPE), and its high sensitivity to NADH. The electrochemical characterization of NiONPs/MCPEs was performed via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical oxidation response of NADH was investigated by differential pulse voltammetry and chronoamperometry. The results indicated that the electrocatalytic effects of NiONPs on the response current of NADH significantly facilitated the electron transfer and improved the performance of the biosensor. Compared to bare carbon paste electrode (BCPE), the oxidation potential was shifted toward more negative potentials and the oxidation current was increased remarkably. Under optimum conditions, NADH could be detected in the range from 1.0 × 10?4 to 1.0 mmol L?1 with lower detection limit (0.05 μmol L?1). The proposed NADH sensor demonstrated fast and reproducible response. Furthermore, an ethanol biosensor was prepared using NiONPs and NAD+-dependent alcohol dehydrogenase enzyme giving linear responses over the concentration range of 1.6 and 38 mmol L?1 of ethanol.  相似文献   

17.
Multiwalled carbon nanotube and ionic liquid-modified carbon ceramic electrode (MWCNT–IL|CCE) was employed for the simultaneous determination of diclofenac and indomethacin (IND). The measurements were carried out by differential pulse voltammetry method in optimal conditions. The prepared electrode showed appropriate voltammetric responses to DCF and IND with 0.225 V difference in the oxidation peak potentials, making fabricated electrode suitable for simultaneous determination of these compounds. The calibration curves were linear over a wide range of concentrations of each species including 0.05–50 μmol L?1 for DCF and 1–50 μmol L?1 for IND. Detection limits were found to be 18 and 260 nM for DCF and IND, respectively. The developed method having good stability and sensitivity was successfully applied for DCF and IND in commercial tablet as well as human blood plasma samples.  相似文献   

18.
《分离科学与技术》2012,47(12):2527-2537
Abstract

The possibility of using Dibenzoylmethane (DBM) for uranium(VI) concentrating by the way of micellar extraction at cloud point temperature and later spectrophotometric determination was investigated. Under the optimum conditions, preconcentration of 50 mL of water samples in the presence of 0.2% (w/v) octylphenoxypolyethoxy ethanol (Triton X‐114), 2×10?4 mol L?1 DBM and 2×10?3 mol L?1 buffer solution (pH=9) gave a limit of detection 11 ng mL?1, and the calibration graph was linear in the range of 15–300 ng mL?1. The recovery under optimum working conditions was higher than 98%.

The proposed method has been applied to the spectrophotometric determination of uranium(VI) in natural water samples after cloud point extraction with satisfactory results.  相似文献   

19.
A new sensitive and selective disposable potentiometric sensor based on polypyrrole (PPy) films for determination of sildenafil citrate (SC) was proposed. The pyrrole polymerization was performed in presence of citrate ions under galvanostatic conditions which resulted in a membrane of PPy doped with citrate anion at graphite pencil electrode surface. Experimental conditions (e.g., pH and conditioning time) and instrumental parameters (e.g., current density and electrical charge) were evaluated in order to reach the best potentiometric response for the proposed sensor. Under optimized conditions, the device presented a linear dynamic range (LDR) for citrate ions concentrations varying from 0.034 to 1.7 mmol L?1 with a Nernstian slope of 57.2 mV dec?1 and a limit of detection (LOD) of 30 µmol L?1. The developed potentiometric sensor was applied for sildenafil citrate (SC) determination (pharmaceutical formulations) and results compared with an official spectrophotometric method indicating a good agreement for a confidence level of 95%. Effect of concomitants species on the potentiometric response of the proposed device and morphologic characterization using microscopy of atomic force (AFM) were realized. The surface roughness of PPy films (synthesized in citrate solution and chloride) showed poorly affected by changing the doping anion, probably because the polypyrrole nodules grow three‐dimensionally simultaneously. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43762.  相似文献   

20.
《分离科学与技术》2012,47(1):203-222
Abstract

The decontamination of lead ions from aqueous media has been investigated using styrene‐divinylbenzene copolymer beads (St‐DVB) as an adsorbent. Various physico‐chemical parameters such as selection of appropriate electrolyte, contact time, amount of adsorbent, concentration of adsorbate, effect of foreign ions, and temperature were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using St‐DVB beads as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at 0.001 mol L?1 acid solutions (HNO3, HCl, H2SO4 and HClO4) using 0.2 g of adsorbent for 4.83×10?5 mol L?1 lead concentration in two minutes equilibration time. The adsorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms over the lead concentration range of 1.207×10?3 to 2.413×10?2 mol L?1. The characteristic Freundlich constants i.e. 1/n=0.164±0.012 and A=2.345×10?3±4.480×10?5 mol g?1 have been computed for the sorption system. Langmuir isotherm gave a saturated capacity of 0.971±0.011 mmol g?1, which suggests monolayer coverage of the surface. The sorption mean free energy from D‐R isotherm was found to be 18.26±0.75 kJ mol?1 indicating chemisorption involving chemical bonding for the adsorption process. The uptake of lead increases with the rise in temperature. Thermodynamic parameters i.e. ΔG, ΔH, and ΔS have also been calculated for the system. The sorption process was found to be exothermic. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.  相似文献   

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