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1.
A flow injection (FI) system was used to develop an efficient on-line sorbent extraction preconcentration system for palladium by graphite furnace atomic absorption spectrometry (GFAAS). The investigated metal was preconcentrated on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The palladium is eluted with 40 μl of HCl 4 M and directly introduced into the graphite furnace. The detection limit for palladium under the optimum conditions was 0.4 ng ml−1. This procedure was employed to determine palladium in different samples. 相似文献
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Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples 总被引:1,自引:0,他引:1
Moawed EA 《Analytica chimica acta》2006,580(2):263-270
The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption (t1/2) of 3.32 min. The variation of the sorption of Pd(II) with temperature gives average values of ΔH, ΔS, ΔG and ΔE to be −38.3 kJ mol−1, −100.7 J K−1 mol−1, −8.3 and 11.8 kJ mol−1, respectively. The sorption capacity of PUFIX was 1.69 mmol g−1 for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D. ≈ 1.24%). The lower detection limit, 1.28 ng mL−1 was evaluated using spectrophotometric method (R.S.D. ≈ 2.46%). 相似文献
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A liquid membrane nonionic surfactant sensitive electrode has been prepared, based on a new barium pseudocationic complex of a highly ethoxylated fatty alcohol polyglycol ether and tetraphenylborate as sensing material. The complex has been incorporated into the plasticized PVC-membrane and used as sensing material.The electrode exhibited positive linear non-Nernstian response toward different nonionic surfactants and sub-Nernstian response toward tetraphenylborate with the lower detection limit of 3.3 × 10−7 mol dm−3 in barium chloride solution.The interfering effect of some alkaline, alkaline earth, and heavy metal cations, has been demonstrated by displaying their calibration curves compared with that of Triton X-100.The electrode has been used as an end-point indicator for potentiometric titration of analytical and technical grade polyethoxylated nonionic surfactants, modelled detergent products, and commercial detergents. 相似文献
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Coimmobilization of beta-galactosidase and glucose oxidase in a redox polymer, polyvinylferrocenium perchlorate (PVF+ ClO4-), led to the development of an enzyme electrode for the determination of lactose. The amperometric response of the electrode was measured at +0.70 V vs. SCE, which was due to the electrooxidation of enzymatically produced H2O2. The effects of the substrate and buffer concentrations as well as the pH on the electrode response were elucidated. 相似文献
6.
A novel long drop time mercury electrode has been constructed from common fused-silica capillary (50 μm I.D., 360 μm E.D.). Proposed device provides reproducible mercury drops with typical lifetime 40-120 s. The electrode was used for a set of electrocapillary measurements aimed at determination of critical micelle concentration of anionic surfactants by a convection controlled drop-time technique. A critical micelle concentration of sodium dodecyl sulfate 5.6 ± 0.4 mmol L−1 and 4.3 ± 0.4 mmol L−1 were obtained in 1 mmol L−1 and 5 mmol L−1 phosphate buffer (pH 7.0), respectively. The values were comparable to those obtained from conductometric measurements under the same conditions (7.0 ± 0.1 mmol L−1 and 5.2 ± 0.1 mmol L−1, respectively) and the difference was explained in accordance with theory of hemi-micelle formation. 相似文献
7.
The construction, performance and application of polymeric membrane (PME) and coated wire (CWE) palladium(II)-selective electrodes based on the ion pair between tetra bromopalladate(II) and hexadecylpyridinium cation (HDP+) in a poly(vinyl chloride) matrix, plasticized with o-NPOE are described. The influence of membrane composition, bromide ion concentration and pH on the potentiometric responses of electrodes were investigated. Nernstian responses were obtained for the two type of electrodes with low limits of detection (1.0×10−6 M for PME and 5.0×10−8 M for CWE). The potentiometric responses are independent of the pH of test solution in the range 3–8. The response time of electrodes are fast (30 s for PME and 10 s for CWE), and they can be used for at least 3 months without any considerable divergence in potentials. The proposed electrodes revealed good selectivity for palladium(II) respect to different cations and anions. They were used to the direct potentiometric determination of palladium(II) in silicon-alumina catalysts. 相似文献
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L. G. Shaidarova A. V. Gedmina I. A. Chelnokova G. K. Budnikov 《Journal of Analytical Chemistry》2006,61(6):601-608
A method for forming a composite film on the surface of a graphite electrode is proposed. Conditions for detecting the maximum catalytic current under batch and flow conditions are determined. A procedure for the electrocatalytic determination of ascorbic acid at the graphite electrode modified with a polyaniline film containing palladium particles is proposed. The catalytic effect of this electrode manifests itself by a ~300-mV decrease in the peak potential of ascorbic acid oxidation and by a multiple increase in the peak current of ascorbic acid oxidation as compared to the unmodified electrode. The linear dependence of the electrocatalytic response of the composite electrode on the concentration of ascorbic acid is observed down to 1 × 10?8 M and 2.5 nmol of ascorbic acid under batch and flow-injection analysis conditions, respectively. 相似文献
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In this paper, multi-walled carbon nanotubes (MWCNTs) were successfully immobilized on the surface of a glassy carbon electrode by mixing with horse-radish peroxidase (HRP). The electrochemical behavior of H2O2 was also studied with the MWCNTs-HRP modified electrode as a working electrode. The MWCNTs-HRP modified electrode showed excellent response of reduction current for the determination of H2O2 at the potential of -300 mV (vs. Ag/AgCl). We assembled the MWCNTs-HRP modified electrode in a thin-layer flow cell and the H2O2 solution was continuously introduced into the cell with a syringe pump. We optimized the sensitivity of the H2O2 sensor by adjusting the working potential and the pH of the buffer solution. The peak current increased linearly with the concentration of H2O2 in the range 3.0 x 10(-7) to approximately 2.0 x 10(-4) mol L(-1). The detection limit is 1.0 x 10(-7) mol L(-1) (S/N = 3). The interferences from ascorbic acid, uric acid and other electroactive substances can be greatly excluded since the sensor can be operated at -300 mV. Stability and reproducibility of the MWCNTs-HRP chemically modified electrode were also studied in this paper. Fabricated with glucose and lactate oxidase, the MWCNTs-HRP electrode was also applied to prepare the on-line glucose and lactate biosensors because of the high sensitivity for the determination of H2O2. 相似文献
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Novel PVC-based coated graphite electrode for selective determination of quinoline yellow 总被引:1,自引:0,他引:1
Novel coated graphite electrode (CGE) for the determination of quinoline yellow (QY), an artificial food colorant, was evaluated based on the use of tetraphenylphosponium-QY ion-pair complex as the electroactive substance. The electrode revealed linear emf-pQY response over wide concentration ranges (1.0 × 10?1 ~ 5.0 × 10?5 M) with a slope ?30.1 ± 0.2 mV decade?1 and a limit of detection of 4.0 × 10?5 M. The electrode showed good stability, reproducibility and fast response (<5 s). It can be used in wide pH range (4.7–10.7) and was successfully applied to determination of quinoline yellow in artificial mixtures and commercial soft drinks. The results obtained with the electrode were in good agreement with the value obtained by using HPLC measurements, as an official method. 相似文献
12.
The surface characteristics of carbon-paste electrodes are greatly improved by spraying the surface with graphite from an aerosol. Significant differences are shown by scanning electron microscopy. The available potential range in different electrolytes is narrower but background currents are decreased and reproducibility is improved, compared to the carbon-paste electrode. With a mercury film and 10-min deposition times, the detection limit for bismuth(III) is 2 × 10-9 M by the differential pulse technique. 相似文献
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Preparation of electrochemically reduced graphene oxide-modified electrode and its application for determination of p-aminophenol 总被引:1,自引:0,他引:1
Su-juan Li De-Hua Deng Huan Pang Lin Liu Yun Xing Shui-Ren Liu 《Journal of Solid State Electrochemistry》2012,16(9):2883-2889
A simple and eco-friendly electrochemical method to reduce graphene oxide precursor was employed for fabrication of graphene sheets modified glassy carbon electrode, and then, the resulting electrode [electrochemically reduced graphene oxide (ERGO)/glassy carbon electrode (GCE)] was used to determine p-aminophenol. The experimental results demonstrated that the modified electrode exhibited excellent electrocatalytic activity toward the redox of p-aminophenol as evidenced by the significant enhancement of redox peak currents and the decreased peak-to-peak separation in comparison with a bare GCE. A highly sensitive and selective voltammetry determination of p-aminophenol is developed using the ERGO/GCE. This method has been applied for the direct determination of p-aminophenol in artificial wastewater. 相似文献
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A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of curcumin and its prodrug, curcumin didecanoate (CurDD), in rat plasma. The analytes were extracted by ethyl acetate following the addition of sodium dodecyl sulfate, and separated on a reverse-phase C(18) column using a gradient mobile phase system of acetonitrile-tetrahydrofuran-water containing 0.1% formic acid. Detection by UV absorption at 425 nm gave a lower limit of quantitation (LLOQ) of 5 and 10 ng/mL for curcumin and CurDD in 50 μL of plasma, respectively. Intra- and inter-day precisions of quality control samples except those at LLOQ were within 15% for curcumin and CurDD, respectively, and the accuracies for both compounds were between 93.9 and 108%. The method was successfully applied to determine plasma concentration-time curves of curcumin and CurDD in rats following intravenous (i.v.) administration of curcumin or CurDD at doses of 1 mg/kg (calculated as curcumin). The results suggested that i.v. dosed CurDD provided sustained plasma levels of curcumin. 相似文献
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A novel approach was proposed for the simple and rapid electrochemical determination of paracetamol (PC) in the presence of uric acid in body fluids. The voltammetric determination of PC is based on the electrochemical reduction of N-acetyl-p-benzoquinoneimine formed simultaneously on the electrochemically treated pencil graphite (ETPG) electrode during the measurement. ETPG electrodes were prepared by the potential cycling between −0.3 V and +2.0 V in 0.1 M H3PO4 solution. The electrochemical performance of the ETPG electrode was evaluated by adsorptive transfer stripping differential pulse voltammetry (ATSDPV). The resulting sensor showed good performance for the determination of PC in human blood serum samples with a linear range of 0.05–2.5 μM and a highly reproducible response (RSD of 3.1%). The calculated detection limit was 2.5 nM (S/N = 3). The proposed method does not require any sample pretreatment, prevents the interference of uric acid and allows the determination of PC directly in blood serum samples. 相似文献
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A novel screen-printing ink consisted of graphite, cellulose acetate and ionic liquid n-octylpyridinum hexafluorophosphate (OPPF) was developed and investigated. The graphite–cellulose acetate system was employed as the basic ink system, which could be easily printed onto the ploy(vinyl chloride) (PVC) substrate. With the natural viscosity and high conductivity of OPPF, the screen-printed electrode (SPE) from the OPPF modified ink exhibited very attractive properties, such as high stability and electrochemical reactivity, low background current and wide electrochemical window. Furthermore, the electrode possessed excellent electrocatalytic activity for the oxidation of dopamine. The linear range for the determination of dopamine was from 1.0 μM to 2.5 mM and the detection limit was 0.5 μM. 相似文献
18.
M. Saber Tehrani M. T. Vardini P. Abroomand Azar S. W. Husain 《Journal of the Iranian Chemical Society》2010,7(3):759-769
A PVC-based membrane containing metoprolol molecularly imprinted polymer (MIP) coated directly on graphite electrode for the determination of metoprolol in real samples is reported. This potentiometric sensor was designed by dispersing the MIP particles in dioctylphthalate plasticizer as solvent mediator and then embedded in polyvinyl chloride matrix. The electrode exhibited a near-Nernstian slope of 55.4 ± 1 mV decade-1 for metoprolol over a wide concentration range between 2.0 × 10-7-8.0 × 10-3 M and a detection limit of 1.3 × 10-7 M. With a response time of about 14 s it could be used for at least 6 months without any divergence in potential. The proposed electrode can be used in the pH range of 3.5-10.5 and can reveal good selectivities for metoprolol over a wide variety of ions. Finally, the designed sensor was successfully applied as an indicator electrode to determine the concentration of metoprolol in tablets, human urine and plasma. The results were compared favorably with those obtained by HPLC method and showed satisfactory agreements with them. 相似文献
19.
The imine of polybenzimidazole (PBI) is chemically oxidized by hydrogen peroxide (H2O2) in the presence of acetic acid (AcOH). Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopies (XPS) showed that when the AcOH concentration remained constant, the degree of oxidation increased with increasing H2O2 levels. Moreover, the imine also exhibited electrochemical redox behavior. Based on these properties, a PBI-modified Au (PBI/Au) electrode was developed as an enzyme-free H2O2 sensor. At an applied potential of −0.5 V vs. Ag/AgCl, the current response of the PBI/Au electrode was linear with H2O2 concentration over a range from 0.075 to 1.5 mM, with a sensitivity of 55.0 μA mM−1 cm−2. The probe had excellent stability, with <5% variation from its initial response current after storage at 50 °C for 10 days. Potentially interfering species such as ascorbic or uric acid had no effect on sensitivity. Sensitivity improved dramatically when multiwalled carbon nanotubes (MWCNT) were incorporated in the probe. Under optimal conditions, the detection of H2O2 using a MWCNT-PBI/Au electrode was linear from 1.56 μM to 2.5 mM, with a sensitivity of 928.6 μA mM−1 cm−2. Analysis of H2O2 concentrations in urine samples using a MWCNT-PBI/Au electrode produced accurate real-time results comparable to those of traditional HPLC methods. 相似文献
20.
We report on a novel tin-bismuth alloy electrode (SnBiE) for the determination of trace concentrations of zinc ions by square-wave anodic stripping voltammetry without deoxygenation. The SnBiE has the advantages of easy fabrication and low cost, and does not require a pre-treatment (in terms of modification) prior to measurements. A study on the potential window of the electrode revealed a high hydrogen overvoltage though a limited anodic range due to the oxidation of tin. The effects of pH value, accumulation potential, and accumulation time were optimized with respect to the determination of trace zinc(II) at pH 5.0. The response of the SnBiE to zinc(II) ion is linear in the 0.5–25?μM concentration range. The detection limit is 50?nM (after 60?s of accumulation). The SnBiE was applied to the determination of zinc(II) in wines and honeys, and the results were consistent with those of AAS. Figure
A novel tin-bismuth alloy electrode was used for determination of trace Zn2+ in wines and honeys by square-wave anodic stripping voltammetry without any deoxygenating. 相似文献