摘要:

AbstractElectroanalytical sensors, suitable for the analysis and monitoring of electroactive analytes present in gaseous phase or low‐conductive liquid media, and based on electrodes in close contact with perfluorinated ion‐exchange polymers are reviewed. The basic operative mechanism of these sensors, in which ion‐exchange polymers act as solid polymer electrolytes (SPE's), is thoroughly discussed, while stressing the fundamental reasons why their behavior differs from that of conventional membrane electrodes. The procedures for preparing composite working electrodes by coating one side of ion‐exchange membranes with stable porous films of conductive materials are described, along with the most common strategies followed to assemble this type of sensors. Useful examples of measurements in electrolyte‐free media of inorganic and organic electroactive species of interest mainly for environmental analysis are given. Future prospects for the development of these sensors are also

ISSN:1040-0397    

DOI:10.1002/elan.1140090602

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThis article describes the determination of Eu by adsorptive cathodic stripping voltammetry after complexation withN‐nitroso‐N‐phenylhydroxylamine (cupferron). The accumulation of the complex at the HMDE was performed at 0.0 V and the subsequent potential scan was made in the square wave mode. The analyte signal occurred at −0.88 V. The detection limit is 0.06 nmol dm−3. The effect of instrumental and chemical parameters on the peak height and potential was investigated. The same technique can be used for the determination of ytterbium and of the other rare earth elements (REEs) after s

ISSN:1040-0397    

DOI:10.1002/elan.1140090603

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractAdsorption isotherms of the ubiquinones UQ4, UQ6, UQ9and UQ10have been determined by two independent voltammetric techniques at the stationary mercury/solution interface. While the redox behavior is essentially the same for all homologues investigated, the molar free enthalpy of adsorption ΔAGincreases steadily with the number of isoprenic units from UQ4to UQ10. In case of UQ10, the experiments have been carried out with three different potentiostatic systems. This allows one to estimate the accuracy of the methods which are direct ones and do not require calibration

ISSN:1040-0397    

DOI:10.1002/elan.1140090604

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIn this article, we have demonstrated the feasibility of using dye binding interactions for the amperometric detection of proteins at conducting polymer coated electrodes with flow injection analysis. Incorporation of appropriate dyes into the conducting polymer during synthesis enables sensitive and selective responses to be obtained. The effects of eluent pH and applied potential on the responses obtained for a range of proteins have been investigated. These parameters can be used to modify selectivity and achieve sensitivity.

ISSN:1040-0397    

DOI:10.1002/elan.1140090605

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe use of a chloride‐containing polypyrrole electrode for the amperometric detection of electroinactive anions subsequent to separation by ion chromatography in suppressed, low conductivity eluent is described. It is demonstrated that changes in selectivity can be obtained by the application of different potential waveforms and current sampling protocols. The approach described is based on the anion dependence of the oxidation/reduction kinetics of the conducting polymer film induced by the applied potentia

ISSN:1040-0397    

DOI:10.1002/elan.1140090606

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSome analytical applications of carbon fiber microelectrodes (CFMEs) modified with cyclic voltammetric electrogenerated poly(3‐methylthiophene) (P3MT) coatings are described. Cyclic voltammograms in aqueous solutions of the phenolic antioxidantstert‐butylhydroxyanisole (BHA),tert‐butylhydroquinone (TBHQ), propylgallate (PG), andtert‐butylhydroxytoluene (BHT) showed that electrocatalytic effects and an improved electrode kinetics occurred at the modified microelectrodes when compared with GC electrodes of conventional size. Moreover, reproducible voltammograms were obtained, obviating the need of cleaning or pretreatment of the coated microelectrode. Another important analytical advantage was the greatly improved resolution for mixtures of analytes. The behavior of P3MT‐CFMEs in organized media was tested by considering their voltammetric response towards the electrochemical oxidation of PG. The nonionic surfactant Pluronic F 68 was selected as the most suitable to form micellar solutions of PG, as well as the emulsifying agent for the preparation of oil‐in‐water emulsions. A 20:80 ethyl acetate:n‐hexane mixture was used as the organic phase and a 0.05 mol L−1H3PO4/H2PO4−buffer solution of pH 2.0 as the aqueous continuous phase. Cyclic voltammetry demonstrated that the PG oxidation current was purely diffusion‐controlled in the organized medium. The analytical characteristics obtained by using differential pulse voltammetry were slightly better than those obtained in aqueous solution. Furthermore, the improved resolution for mixtures of analytes is retained in the oil‐in‐water emulsified medium. The proposed method was applied with good results to the determination of PG in spiked commercial dehydrated soup samples by direct emulsification of aliquots of the sample extract in the ethyl

ISSN:1040-0397    

DOI:10.1002/elan.1140090607

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe voltammetric behavior of sulfadimetoxol (SDX) was studied by square‐wave techniques, leading to two methods for its determination in aqueous samples and veterinary formulations. The application of the square‐wave mode shows the determination of SDX between 1 × 10−7M and 2 × 10−6M at −0.60 V and for the stripping voltammetry of adsorbed SDX with an accumulation step of 15 s proved to be more sensitive, yielding signals five times larger than those obtained without the accumulation. The determination of SDX was done between 2 × 10−8M and 5 × 10−7M by stripping mode. The relative standard deviations obtained for concentration levels of SDX as low as 3 × 10−7M with square‐wave was 3.4 % (n= 8) and for 2 × 10−7M with stripping square‐wave was 3.1 % (n= 8). The methods were satisfactorily applied for determining SDX

ISSN:1040-0397    

DOI:10.1002/elan.1140090608

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) (PVC)‐based membrane of pentathia‐15‐crown‐5 exhibits good potentiometric response for Hg2+over a wide concentration range (2.51 × 10−5to 1.00 × 10−1mol dm−3) with a slope of 32.1 mV per decade of Hg2+concentration. The response time of the sensor is as fast as 20 s. The electrode has been used for a period of six weeks and exhibits fairly good discriminating ability towards Hg2+in comparison to alkali, alkaline and some heavy metal ions. The electrode can be used in the pH range

ISSN:1040-0397    

DOI:10.1002/elan.1140090609

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe epoxy‐impregnated graphite tube electrode bulk modified with 2‐mercaptobenzoxazole, employed in a wall‐jet configuration, was found to be useful for the continuous flow and flow injection stripping voltammetric determinations of AgI, HgIIand BiIII. For continuous flow, detection limits for AgI, HgIIand BiIIIwere 1.8 × 10−10M, 1.9 × 10−9M and 9.5 × 10−9M, respectively (10 min accumulation,S/N= 3). Precisions for 5.00 × 10−9M AgI, 1.00 × 10−8M HgIIand 1.00 × 10−7M BiIIIwere 10.5%, 5.77 % and 7.90% (relative standard deviations,n= 6), respectively. In the case of flow injection stripping, with a 500 μL injection loop, detection limits of 0.59 ng, 2.0 ng and 120 ng were obtained for AgI, HgIIand BiIII, respectively (S/N= 3). Selected metal ions, inorganic and organic substances were investigated for interferences. The electrode was tested with a certified sample and then applied to the determinations of the metal ions in a urin

ISSN:1040-0397    

DOI:10.1002/elan.1140090610

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe electrochemical behavior of the water‐soluble C60–γ‐CD (1:1) inclusion complex has been studied on the hanging mercury drop electrode. A one‐electron reversible adsorptive electroreduction and three irreversible adsorptive electroreductions were detected by cyclic voltammetry. The amount of C60–γ‐CD adsorbed at saturation is 1.73 × 10−11mol/cm2, the diffusion coefficient is 5.81 × 10−6cm2/s, and the standard rate constant of the surface reaction ksare 0.888 s−1, 0.853 s−1and

ISSN:1040-0397    

DOI:10.1002/elan.1140090611

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY