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1.
Sylvia Sander 《Analytical and bioanalytical chemistry》1999,365(5):435-443
Four different complexing reagents namely chloranilic acid, oxine, tropolone, and cupferron were applied for AdSV determinations
of molybdenum. The parameters for the determination using a flow-through cell with a hanging mercury drop (HMDE) as working
electrode were examined systematically for all four systems and evaluated. Cyclic voltammograms were recorded to examine the
electrode reaction, alternating current (AC) voltammetry was used to determine adsorption processes. The comparison includes
sensitivity, detection limit, linear concentration range, the susceptibility to interference by organic compounds or foreign
ions, and the applicability to sea and tap water samples. The interpretation of the electrode reaction mechanism for the reduction
of the Mo cupferron complex published from Jiao et al. [10] was improved.
Received: 12 February 1999 / Revised: 10 May 1999 / Accepted: 14 May 1999 相似文献
2.
N. Alizadeh S. Ershad H. Naeimi H. Sharghi M. Shamsipur 《Fresenius' Journal of Analytical Chemistry》1999,365(6):511-515
A PVC membrane electrode for copper(II) ions based on a recently synthesized naphthol-derivative Schiff’s base as membrane
carrier was prepared. The sensor exhibits a Nernstian response for Cu2+ ions over a wide concentration range (5.0 × 10–6–5.0 × 10–2 mol/L) with a detection limit of 3.1 × 10–6 mol/L (0.2 μg/mL). It has a very short response time of about 5 s and can be used for ?3 months without any divergence in
potential. The proposed electrode revealed good selectivities over a wide variety of other cations including alkali, alkaline
earth, transition and heavy metal ions and could be used in a pH range of 4.0–7.0. It was successfully applied to the direct
determination and potentiometric titration of copper ion.
Received: 23 February 1999 / Revised: 4 May 1999 / Accepted: 5 May 1999 相似文献
3.
Malgorzata Grabarczyk 《International journal of environmental analytical chemistry》2013,93(9):1008-1018
This paper reports the use of an adsorptive voltammetric technique for Pb(II) determination using cupferron as a selective complexing agent. After accumulation of the complex onto a hanging mercury drop electrode, the electrode potential was scanned with differential pulse modulation and the reduction current of lead was observed at about??0.5?V. Under optimum conditions (5?×?10?4?mol?L?1 cupferron concentration, 0.1?mol?L?1 acetate buffer (pH 5.5), adsorption at??50?mV for 30?s) the detection limit was 5.1?×?10?10?mol?L?1. The relative standard deviation of five measurements for low lead concentration was 3.1%. The accuracy of the method was tested by analysing certified reference material (SPS-WW1 Waste Water). Finally, the method was successfully applied to the determination of Pb(II) in river water samples without any pretreatments. 相似文献
4.
D. Dobnik M. Kolar J. Komljenovi Nj. Radi 《Fresenius' Journal of Analytical Chemistry》1999,365(4):314-319
The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements
of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response
of the electrode to Cu2+ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper
(II) in batch experiments down to concentrations of 1 × 10–5 mol L–1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow-injection analysis for Cu
(II) and/or iodide determinations.
Received: 4 December 1998 / Revised: 31 March 1999 / Accepted: 6 April 1999 相似文献
5.
Adsorptive Cathodic Stripping Voltammetric Method for Determination of Gallium Using an In Situ Plated Lead Film Electrode
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The in situ plated lead film electrode was proposed for the first time for adsorptive stripping voltammetric determination of gallium in water samples. The method was based on simultaneous lead film formation and Ga(III)‐cupferron complex preconcentration at ?0.7 V and its cathodic stripping during the potential scan. The composition of the supporting electrolyte, cupferron concentration, conditions of lead film formation, potential and time of accumulation were studied in detail. Under optimum conditions the limit of detection was 3.8×10?9 mol L?1. The proposed procedure was validated in the course of Ga(III) determination in waste water certified reference materials. 相似文献
6.
Characterization and application of an electrode modified by mechanically immobilized copper hexacyanoferrate 总被引:1,自引:0,他引:1
A newly modified electrode was prepared by mechanical immobilization of copper hexacyanoferrate (CuHCF) on a graphite electrode.
The modified electrode was characterized by cyclic voltammetric experiments. The effect of different background electrolytes,
pHs and scan rates on the electrochemical behaviour of the electrode has been evaluated. In NH4Cl two reversible redox peaks were observed. The first redox peak corresponding to Cu+/Cu2+ is observed only in this medium. The second redox peak corresponds to the Fe(CN)6
4–/Fe(CN)6
3– couple. Both anodic peaks were used for catalytic oxidation of ascorbic acid. As the anodic current for catalytic oxidation
was proportional to the amount of ascorbic acid, an analytical method was developed for the determination of ascorbic acid
in commercial samples.
Received: 26 May 1998 / Revised: 15 March 1999 / Accepted: 20 March 1999 相似文献
7.
Electrochemical reduction of vanadium(V) complex with cupferron (N‐nitroso‐N‐phenylhydroxylamine), VVO(cupf)2OH, has been studied by polarography in wide potential range to verify the catalytic mechanism of electroreduction of coordinated cupferron ligand. Reduction of the complex was studied in the concentration range from 2 ? 10?5 M to 10?3 M. Depending on the process conditions kinetics of catalytic reduction of coordinated cupferron is either controlled by adsorption step or governed by mixed control of diffusion and chemical reaction. Kinetic parameters of the reduction process are reported. Reduction of VVO(cupf)2OH complex is accompanied by adsorption and autoinhibition phenomena. V(II) ion in the surface bound complex of vanadium with cupferron catalyzes reduction of coordinated cupferronate ligands. In 1 mM solutions, the catalytic reduction of coordinated cupferron ligand shifts to more cathodic potentials due to formation of a monolayer of adsorbed vanadium(III)‐cupferron complexes. Reduction kinetics in the presence of tetraalkylammonium salt is consistent with multilayer cooperative adsorption of anionic vanadium(II)‐cupferron complex and tetraalkylammonium cations. 相似文献
8.
Y?etsu Danzaki Kunio Takada Kazuaki Wagatsuma 《Fresenius' Journal of Analytical Chemistry》1998,362(4):421-423
For the determination of Ta (> 0.0005 mass %) in iron and low-alloy steel spectrophotometric methods, e.g., after the extraction
of the Ta-Victoria Blue B complex by benzene, are generally used. To avoid the application of poisonous benzene as extracting
solvent and to improve the detection power, an ICP-AES method after the separation of Ta by coprecipitation with cupferron
has been developed. The detection limit (3σ) of 0.6 μgTa/g is lower in comparison with spectrophotometric methods. Therefore,
the method also allows the determination of Ta-concentrations in the μg/g-range in high-purity iron.
Received: 26 February 1998 / Revised: 4 May 1998 / Accepted: 10 May 1998 相似文献
9.
10.
We report on a simple and reliable method for the determination of trace cadmium ion using a glassy carbon electrode (GCE) modified with cupferron, ß-naphthol and MWCNTs. The operational mechanism consists of several steps: first, the ligand cupferron on the modified electrode reacts with Cd2+ ion to form a chelate compound. Next, this chelate is adsorbed by the carrier ß-naphthol following the principle of organic co-precipitation. Finally, the coprecipitated complex is detected by the GCE. This scheme is interesting because it combines preconcentration and electrochemical detection. Two linear responses are obtained, one in the concentration range of 5.0?×?10?11 to 1.6?×?10?8 M, the other in the range of 1.6?×?10?8 to 1.42?×?10?6 M, with a lower detection limit of 1.6?×?10?11 M. This modified GCE does not suffer from significant interferences by Cu(II), Hg(II), Ag(I), Fe(III), Pb(II), Cr(III), Zn(II), NO3?, Cl?, SO 4 2? ions and EDTA. The response of the electrode remained constant for at least 3 weeks of successive operation. The method presented here provides a new way for the simultaneous separation, enrichment, and electrochemical detection of trace cadmium ion. Figure
Separation, enrichment and electrochemical detection of trace cadmium ion were simultaneously and synchronously carried through on the electrode modified with cupferron, ß-naphthol, and multiwalled carbon nanotubes. It shows higher selectivity, excellent sensitivity and good stability. 相似文献
11.
A differential pulse adsorptive stripping voltammetric method has been developed for molybdenum trace determination in environmental water samples containing organic compounds. It was proved that interferences from the organic matrix such as surface active substances and humic substances could be removed by the addition of resin to the analysed sample prior to voltammetric measurement. The parameters for Mo(VI) determination in the presence of resin, using a hanging mercury drop as the working electrode, were examined systematically for two complexing agents: cupferron and chloranilic acid. The detection limits estimated from 3 times the standard deviation for a low Mo(VI) concentrations were equal to 5 × 10−11 and 3 × 10−10 mol L−1 for cupferron and chloranilic acid, respectively. At the optimized conditions the quantitative Mo(VI) determination in the presence of even 50 mg L−1 of surface active compounds can be performed. The proposed procedures were validated in the course of Mo(VI) determination in certified reference material NASS-5 and in the course of studying recovery of Mo(VI) from spiked river water samples. 相似文献
12.
A new modified electrode was prepared by electrodeposition of caffeic acid (CFA) at the surface of an activated glassy carbon
electrode. Cyclic voltammetry was used to investigate the redox properties of this electrode at various solution pH values
and at various scan rates. The pH dependence of the electrode response was found to be 58.5 mV/pH, which is very close to
the expected Nernstian value. The electrode was also employed to study electrocatalytic oxidation of reduced nicotinamide
adenine dinucleotide (NADH), using cyclic voltammetry, chronoamperometry and rotating disk voltammetry as diagnostic techniques.
It was found that the modified electrode exhibits potent and persistent electrocatalytic properties toward NADH oxidation
in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 450 mV compared to the process at an
unmodified electrode. The electrocatalytic current increases linearly with NADH concentration in the range tested from 0.05
to 1.0 mM. The apparent charge transfer rate constant and transfer coefficient for electron transfer between the electrode
surface and immobilized CFA were calculated as 11.2 s−1 and 0.43, respectively. The heterogeneous rate constant for oxidation of NADH at the CFA-modified electrode surface was also
determined and found to be about 3 × 103 M−1 s−1. Finally, the diffusion coefficient of NADH was calculated as 3.24 × 10−6 cm2 s−1 for the experimental conditions, using chronoamperometric results.
Received: 6 January 1999 / Accepted: 11 May 1999 相似文献
13.
An electrochemical method for quantification of the radical scavenging activity of SOD 总被引:1,自引:0,他引:1
F. Lisdat B. Ge R. Reszka E. Kozniewska 《Fresenius' Journal of Analytical Chemistry》1999,365(6):494-498
An electrochemical technique for the determination of enzymatic superoxide scavenging activity is described. In amperometric
mode of sensor operation ?the oxidation current was altered by additions of superoxide dismutase (SOD). The 50% inhibition
value (I50) corresponded to 0.165 U of the standard photometric test of McCord and Fridovich. Influence by inert proteins
was much less than in the standard method: The SOD/BSA ratio was 4 × 105. Potentially interfering substances, e.g. ascorbic acid and glutathione, were tested. Plasma samples of rats which were treated
with modified SOD during cerebral ischaemia, were assayed with the new method and the standard photometric test. A good correlation
was found for the analysis in these physiological samples (r = 0.97).
Received: 3 February 1999 / Revised: 17 May 1999 / Accepted: 19 May 1999 相似文献
14.
镓-铜铁试剂络合物的极谱催化波 总被引:4,自引:1,他引:3
本文研究了镓的吸附催化波的示波极谱性能,并对催化波的性质,影响因素,干扰及分离方法等进行了试验。确定了最适宜的分析条件。同时,测定了两种矿样中的镓并与罗丹明B比色法对照,结果满意。 相似文献
15.
《Electroanalysis》2003,15(21):1687-1692
Interfacial activity of uranium(VI)‐cupferron and uranium(VI)‐chloranilic acid (CAA) complexes (in 0.1 M acetate buffer pH 4.6 or 0.1 M NaClO4 respectively) on polarized mercury electrode at 110 mV, 10 mV or ?240 mV respectively vs. saturated calomel electrode (SCE), and under conditions of the application of adsorptive stripping voltammetric techniques was studied. It revealed a competitive effect of interfacial activity of the mentioned complexes consisting in a nonmonotonous effect of the bulk concentration of U(VI) on the adsorption of the mentioned complexing reagents at their constant concentrations. At concentrations lower than 5×10?5 mol L?1 the complexes U(VI)‐cupferron or U(VI)‐CAA exhibited a relatively strong electrosorption providing the adsorption coefficients β of the order 104 L mol?1, the maximum surface excess Γm ≈ 5 to 10 μmol m?2 and average Frumkin interaction coefficients reaching their absolute values 2 to 2.6. 相似文献
16.
M. F. S. Teixeira L. A. Ramos E. Almeida Neves O. Fatibello-Filho 《Analytical and bioanalytical chemistry》2000,367(1):86-89
The construction and the application of a silica gel based carbon-epoxy indicator electrode for the potentiometric determination
of acids and bases are described. The effect of composition of silica gel and carbon-epoxy, slope (mV/pH), linear response
(pH range) and the use for acid-base titrations were investigated. The data obtained for the acid-base titrations were compared
with those obtained using a glass electrode in the same conditions. The electrode showed a linear response in the pH 2 to
13 range with a slope of –40.5 ± 0.4 mV/pH (at 25 °C) and a response time of less than 15 s. The lifetime of the electrode
was higher than one year (over 6000 determinations) with a decrease of only 5% of the initial potentiometric response. The
silica gel based carbon-epoxy electrode showed excellent results in the end-point indication potentiometric titrations in
determination of acids and bases. The miniaturization of the proposed electrode for flow injection analysis was investigated.
Received: 11 August 1999 / Revised: 4 October 1999 / Accepted: 7 October 1999 相似文献
17.
A nickel hexacyanoferrate modified electrode was constructed by mechanical immobilization. A reversible peak with midpoint
potential of 0.38 V was observed in cyclic voltammetry with 0.1 M NaNO3. Electrocatalytic oxidation of thiosulfate was effective on the modified electrode at a significantly reduced overpotential
of 0.5 V and at broad pH range. The modified electrode can be used for the determination of thiosulfate in the concentration
range of 7.0 × 10–4 to 5.6 × 10–3 M. It has been used for the amperometric determination of thiosulfate in photographic effluents. The results obtained were
in good agreement with those obtained by other methods.
Received: 27 January 1999 / Revised: 5 July 1999 / Accepted: 7 July 1999 相似文献
18.
Separation and direct UV detection of lanthanides complexed with cupferron by capillary electrophoresis 总被引:1,自引:0,他引:1
Separation and detection of lanthanides by capillary zone electrophoresis in the presence of cupferron (N-nitroso-N-phenylhydroxylamine) as UV absorbing complexing agent were investigated. The resolution of partially complexed positively charged cupferron complexes is improved by using a buffer ligand competing with cupferron for metal ions. When hydroxyisobutyric acid (HIBA) is used as buffer and competing ligand, it provides complete separation of all 14 lanthanides with good peak shapes. An on-column separation of 14 lanthanides was achieved in only 7 min using 0.1 mmol/l cupferron, 15 mmol/1 HIBA at pH 4.9. The separation efficiencies for the optimum separation condition are between 77,000 and 208,000 theoretical plates. Determination of lanthanide complexes was performed by direct UV detection at 210 nm. Detection limits (signal-to-noise ratio=3) are ca. 0.24-0.47 microg/ml for lanthanides. Under optimum conditions, the complete separation of thorium and uranium from mixed lanthanides was achieved. 相似文献
19.
S. M. V. Fernandes J. L. F. C. Lima A. O. S. S. Rangel 《Analytical and bioanalytical chemistry》2000,366(1):112-115
A flow injection system for the automatic determination of total phosphorus in beer is described. The developed manifold
uses a two-stage photooxidation/thermal digestion procedure together with oxidizing and hydrolyzing reagents to convert all
forms of phosphorus compounds to orthophosphate. Polyphosphates are hydrolyzed by acid and heat, and organo-phosphates are
digested by UV-catalyzed peroxodisulfate oxidation. The orthophosphate formed is then spectrophotometrically determined by
the phosphomolybdenum blue reaction, using stannous chloride as reducing agent. The results obtained for a set of 19 beer
samples (with concentrations from 120 to 735 mg P/L) were in good agreement with the reference method, the maximum relative
deviation found being 4.7%. Relative standard deviations for ten consecutive determinations were lower than 1.5%, and a detection
limit of 1 mg P/L was achieved.
Received: 18 May 1999 / Revised: 5 July 1999 / Accepted: 7 July 1999 相似文献
20.
Application of a hexapole collision and reaction cell in ICP-MS Part I: Instrumental aspects and operational optimization 总被引:1,自引:0,他引:1
I. Feldmann N. Jakubowski D. Stuewer 《Fresenius' Journal of Analytical Chemistry》1999,365(5):415-421
The application of an ion-guiding buffer gas-filled hexapole collision and reaction cell in ICP-MS has been studied in order
to give a preliminary performance characterization of a new instrument providing this feature for increasing the ion yield
and decreasing contributions from Ar induced interfering molecular ions. As buffer gas He was used while H2 served as reaction gas. Addition of the latter can be an effective means for reduction of typical argon induced polyatomic
ions (Ar+, ArO+, Ar2
+) by orders of magnitude owing to gas phase reactions. Molecular interferences generated in the cell can be suppressed by
a retarding electric field established by a dc hexapole bias potential of –2 V.
Received: 10 May 1999 / Revised: 4 June 1999 / Accepted: 12 June 1999 相似文献