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Jang‐Hee Yoon G. Muthuraman JeeEun Yang Yoon‐Bo Shim Mi‐Sook Won 《Electroanalysis》2007,19(11):1160-1166
Pt‐nanoparticles were synthesized and introduced into a carbon paste electrode (CPE), and the resulting modified electrode was applied to the anodic stripping voltammetry of copper(II) ions. The synthesized Pt‐nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy and X‐ray photoelectron spectroscopy techniques to confirm the purity and the size of the prepared Pt‐nanoparticles (ca. 20 nm). This incorporated material seems to act as catalysts with preconcentration sites for copper(II) species that enhances the sensitivity of Cu(II) ions to Cu(I) species at a deposition potential of ?0.6 V in an aqueous solution. The experimental conditions, such as, the electrode composition, pH of the solution, pre‐concentration time, were optimized for the determination of Cu(II) ion using as‐prepared electrode. The sensitivity changes on the different binder materials and the presence of surfactants in the test solution. The interference effect of the coexisted metals were also investigated. In the presence of surfactants, especially TritonX‐100, the Cu(II) detection limit was lowered to 3.9×10?9 M. However, the Pt‐nanoparticle modified CPE begins to degrade when the period of deposition exceeds to 10 min. Linear response for copper(II) was found in the concentration range between 3.9×10?8 M and 1.6×10?6 M, with an estimated detection limit of 1.6×10?8 M (1.0 ppb) and relative standard deviation was 4.2% (n=5). 相似文献
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Kanchi Suvardhan Kailasa Suresh Kumar Dasari Rekha Pantrangam Subrahmanyam Kapuvedi Kiran Bellum Jayaraj Surasura Ramanaiah Kandhukuri Janardhanam Pattium Chiranjeevi 《Mikrochimica acta》2007,157(3-4):237-244
Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate
(2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed
with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished
by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully
applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL
sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL−1. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL−1), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium
in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test. 相似文献
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Electroanalytical methods are highly selective for measuring electrical quantities including the charge, potential and current with their relation to chemical parameters. They are widely applied in various fields such as biochemical analysis, industrial quality control and environmental monitoring. They have many advantages over other techniques in that they are not time consuming and are specific for certain oxidation states of certain elements which give these techniques high selectivity and sensitivity features. This paper is based on two parts: the first part describes the fabrication of screen‐printed electrodes (SPEs) modified with methyl red as electroactive material, while second part describes the preparation and characterization of Fe(II)–methyl red complex using various spectroscopic tools, the complex being used for the construction of carbon paste electrodes (CPEs). The two proposed electrodes were successfully applied for the determination of Fe(II) in water and pharmaceutical (pharovit) samples. The electrodes under investigation show potentiometric response for Fe(II) in the concentration range 8.0 × 10?7–1.0 × 10?2 and 5.0 × 10?7–1.0 × 10?2 M at 25°C for SPE and CPE, respectively, and the electrode response is independent of pH in the range 1.5–7.0. These sensors show Nernstian slopes of 29.1 ± 0.2 and 29.7 ± 0.16 mV decade?1 with detection limit values of 8.0 × 10?7 and 5.0 × 10?7 M for SPE and CPE, respectively. These electrodes show fast response time of 6 and 4 s and exhibit a lifetime of 100 and 30 days for SPE and CPE, respectively. The mechanism of chemical reaction between modifier and Fe(II) on the SPE surface was studied using infrared spectra, scanning electron microscopy and energy‐dispersive X‐ray analysis. The proposed potentiometric method was validated according to the IUPAC recommendations. The results obtained using the proposed sensors were comparable with those obtained with inductively coupled plasma analysis. 相似文献
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Bin Hu 《International journal of environmental analytical chemistry》2013,93(12):927-934
In this article, the contents and distribution of total chromium, Cr(III) and Cr(VI) in various cigarettes and cigarette ashes were determined by using a cloud point extraction (CPE) separation/preconcentration combined with graphite furnace atomic absorption spectrometric (GFAAS) detection. Different extraction reagents, such as tetramethylammonium hydroxide (TMAH), Na2HPO4, Na2CO3/NaOH, NaOH and H2O, were tested for the extraction of Cr species, and the extraction efficiency was estimated. The experimental results showed that TMAH was the most efficient extraction reagent for the analyte in cigarette samples. By using the established method, the total chromium, Cr(III) and Cr(VI) in various cigarettes and cigarette ashes were determined and their distribution was studied. It was found that Cr(III) is a main species in cigarettes, but that it can be partly oxidized to Cr(VI) during smoking. 相似文献
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We previously reported that the peptide containing a Cys-Pro ester (CPE) moiety is spontaneously transformed into a peptide thioester via an N to S acyl shift followed by diketopiperazine formation. In an attempt to identify more reactive structures for the formation of a peptide thioester, we modified the CPE structure, in which the Pro residue in the CPE moiety was replaced with N-substituted glycine derivatives. These peptides were transformed into a peptide thioester more rapidly. Alternatively, the addition of an amino acid residue at the C-terminus of the CPE moiety also accelerated thioester formation. 相似文献
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N. Stipanelov Vrandečić I. Klarić U. Roje 《Journal of Thermal Analysis and Calorimetry》2001,65(3):907-918
The thermal degradation of poly(vinyl chloride)/chlorinated poly(ethylene) (PVC/CPE) blends of different compositions was
investigated by means of dynamic and isothermal thermogravimetric analysis in flowing atmosphere of nitrogen. Kinetic parameters
(the apparent activation energy E, and pre-exponential factor Z) were calculated after Flynn-Wall-Ozawa method for the first stage of dynamic degradation of PVC/CPE blends, and after Flynn
method for the isothermal degradation. In both cases, there is the compensation dependence between the values E and logZ. The values of compensation ratios as well as the characteristics of TG and DTG curves, confirm the stabilizing effect of
CPE on PVC dehydrochlorination.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Liquid phase microextraction applications in food analysis 总被引:2,自引:0,他引:2
Asensio-Ramos M Ravelo-Pérez LM González-Curbelo MÁ Hernández-Borges J 《Journal of chromatography. A》2011,1218(42):7415-7437
Over the last years, liquid-phase microextraction (LPME) in its different application modes (single drop microextraction, dispersive liquid-liquid microextraction and hollow fiber-LPME) has been increasingly applied for the extraction of both inorganic and organic analytes from different matrices. Its advantages over conventional extraction procedures (simplicity, effectiveness, rapidity and low consumption of organic solvents) has also attracted its application in the complex food analysis field, in which it has clearly provided good and challenging results. A comprehensive review dealing with those articles published since its introduction till the end of March 2011 is presented, offering also a critical vision of the analytical potential of LPME for the analysis of foods. 相似文献
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GuoHua Zhang 《中国科学 数学(英文版)》2012,55(5):913-936
In the past twenty years,great achievements have been made by many researchers in the studies of chaotic behavior and local entropy theory of dynamical systems.Most of the results have been generalized to the relative case in the sense of a given factor map.In this survey we offer an overview of these developments. 相似文献