摘要:

AbstractA review is geven on solid‐state amperometric sensors designed for the detection of gaseous analytes. Attention is geven primarily to sensors used in the absence of a bulk liquid phase that have been reported in the literature since 1992, although a historical perspective is presented. The review is limited to sensors employing solid polymer electrolytes, transition metal powders, and inorganic materials prepared by sol‐gel processes as the solid‐state electrylyte. The wide applicability of solid atate sensors to gas phase species is demonstrated through numerous examples. Analytes determined include O2, H2, CO, NO2, NH3, an

ISSN:1040-0397    

DOI:10.1002/elan.1140090202

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe electrocatalytic oxidation of hydrogen peroxide in solution at a modified carbon fiber electrode has been investigated. A simple electrochemical procedure has been developed to dramatically improve the voltammetry for the peroxide, NADH, and several other species under steady state and fast scan voltammetry. The surface is generated by the electrochemical oxidation of NASH followed by exposure to peroxide. This procedure yields a surface which is sensitive to peroxide and stable in air for more than 90 days. This oxidation occurs at a potential such that it is easily discriminated from the analytes tested in this study.

ISSN:1040-0397    

DOI:10.1002/elan.1140090203

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe electroanalytical performance at three electrodes: DNA‐modified galssy carbon electrode, mercury thin film electrode and glassy carbon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, depenent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carbon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA‐modified galssy carbon electrode enables a lower detection limit of 1.0 μM owing to the preconecentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carbon electr

ISSN:1040-0397    

DOI:10.1002/elan.1140090204

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractChemically modified electrode (CME) exhibting electrocatalytic response toward hemoglobin (Hb) is constructed by constructed by absorbing the riboflavin mediator onto spectroscopic graphite surface. The electron transfer between the riboflavin functionality and the graphie is fast. The surface coverage is at most 9.6 × 10−10mol cm−10. The modified electrode permits the electroreduction of hemoglobin to take place at a low potential corresponding to the reduction potential of the mediator molecule. For neutral and slightly acidic solutions, this corresponds to very modest negative potentials (vs.Ag/AgCi). Characterization of the performance of the CME is carried out. After 30 min of continuous potential scanning of pH6.8, 60% of the original coverage remains for the CME. The linear range of the calibration plot is 30–480 μmol/L. The effect of the solution pH on the electrocatalytic activity of the CME for hemoglobin reduction is investigated. Due to its high sensitivity and durability, this CME coulde be used as an analytical sensor for detecting hemoglobin in real

ISSN:1040-0397    

DOI:10.1002/elan.1140090205

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractPeptide nucleic acids (PNA) are new DNA analogs which offer great promise for highly specific DNA biosensors, for use as antisense drugs, or for various molecuilar biology applications. This article evaluates the interfacial behavior of PNA at carbon paste electrodes, in comparison to DNA. While both PNA oligomers display a strong adsorption onto the carbon surface, they differ intheir interfacial properties due to differences in change and structure. Factors influencing the adsorption behavior, including the adsorption potential or time, PNA concentration, coexisting anions and cations, or buffer concentration, are explored. The strong adsorption is exploited for an effective preconcentration step prior to the chronopotentiometric measurement. The resulting adsorptive stripping potentiometric protocol offers convenient quantitation of ng/mL levels of PNA, as desired for future diagnostic, pharmaceutical and biological applications of these DNA analogs.

ISSN:1040-0397    

DOI:10.1002/elan.1140090206

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe use of platinum‐and gold‐ultramicroelectrode arrays for heavy metal analysis is described. The noble metal microelectrodes are structured with standard silicon technologies. The geometry of the electrode array is varied and optimized in regard to the microelectrode characteristic. Mercury film formation and–dissolution on platinum microelectrode arrays is characterized and compared with iridium electrodes of the same geometry. Gold microelectrode arrays are shown to be useful for mercury detection. The repeated use of the sensors has been studied. Optimizing the electrode gemoetry and the stripping procedure results in detection limits down to the ng/L

ISSN:1040-0397    

DOI:10.1002/elan.1140090207

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA direct, continuous method for the measurement of peroxodisulfate anion has been devised and assessed. The approach is based upon the reduction of the anion under mass transfer limiting conditions at an amalgamated copper rotating disk electrode. The preparation of the disk electrode by Hg electroplating was examined in detail in order to generate a reproducible surface. The system was calibrated by demonstrating that the limiting current density for peroxodisulfate reduction was directly proportional to its bulk solution concentration. An electrochemical cell arrangement was then developed to permit the continuous, in situ measurement of peroxodisulfate concentration during electrochemical synthesis.

ISSN:1040-0397    

DOI:10.1002/elan.1140090208

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSimple two‐electrode potential sweep and potential step electrochemical measurements are reported in a perfused living rat heart prepared using a modified in situ Langendorff preparation. Cyclic voltammetry of Ru (NH3) 63+at Pt electrodes is performed in vivo after retrograde aortic perfusion of Ca2+‐and albumin‐free, oxygenated Krebs buffer containing Ru(NH3) 63+to assess uniformity of perfusion. Four types of voltammetric response are observed depending on the placement of the working electrode. These types are distinguished on the basis of the relative contributions of diffusive and hydrodynamic mass transport as mnifest in the shapes of the current‐potential curves. Chronoamperometric measurement of double layer charging was used to estimate extracellular tissue resistance. These chronoamperometric experiments are performed in buffer solutions by small potential steps around a set potential of non‐Faradaic activity. Tissue. resistance was estimated to be ca. 598 ± 138 Ω from the chronoamperometric data. The electrochemical responses observed from both measurements exhibit good reproducibility between individual hea

ISSN:1040-0397    

DOI:10.1002/elan.1140090209

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe use of a tungsten oxide electrode for potentiometric flow‐injection analysis of transition metal ions is described. The effect of a variety of experimental conditions, including the carrier pH, the types of ligands and their concentrations, was studied. It was found that the best sensitivity for the ions tested was obtained using EDTA as a ligand. The electrode exhibited a linear response for Fe3+, Cu2+, Pb2+and Ca2+in the range of 2.5 × 10−4M to 2 × 10−3M using with 1 × 10−3M EDTA at pH 5.0 as carrier. The detection limits were found to be between 1 × 10−5to 5 × 10−5M. Reproducibility for Fe3+was about 1.7% with a stable ba

ISSN:1040-0397    

DOI:10.1002/elan.1140090210

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA rapid and highly sensitive adsorptive stripping voltammetry method for the measurement of traces of nickel(II) in flowing systems is described. The method involves a mass‐transport controlled preconcentration step, during which the NiII‐dimethylglyoxime complex is adsorbed onto an in situ plated mercury film wall‐jet electrode, followed by a reductive square wave stripping scan. The optimization of the experimental conditions and square wave parameters was carried out in order to achieve high sensitivity, reproducibility and fast response. The detection limit, restricted by the amount of nickel in the blank solution, was found to be 1.3 × 10−10M, with a relative standard deviation of ±12.2% (n= 15), for a 1‐min accumulation time. Linear calibration plots were obtained up to 8 × 10−10M. This method can be applied to continuous on‐line monitoring of trace levels of nickel in flowing systems, enabling

ISSN:1040-0397    

DOI:10.1002/elan.1140090211

出版商:VCH Verlagsgesellschaft mbH    

年代:1997

数据来源: WILEY