摘要:

AbstractThis review discusses electroanalysis with interdigitated array (IDA) microelectrodes. The basic electrochemical properties of IDAs are presented along with a calculation of diffusion‐controlled current and an example of generation collection voltammetry to clarify the advantages of IDA for electroanalysis. The fabrication procedures of metal and novel carbon based IDAs are also summarized because the fabrication of very small IDAs is advantageous for electroanalysis. Previously reported electroanalytical applications of IDAs are overviewed. Among them are the measurement of redox electron conduction and molecular diffusion in various films, various types of enzyme sensors and electrochemical switches, an example of highly sensitive and selective generation collection voltammetry, a new stripping analysis using self‐induced redox cycling and the detectors for flow cells and liquid chromatogra

ISSN:1040-0397    

DOI:10.1002/elan.1140070702

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe combination of a novel electrode design and a new experimental approach to coulometry permits the analysis of microliter amounts of samples without prior calibration. The technique has been applied to the determination of lead in whole blood standards. The time for one analysis is 4min and the relative precision approximately 5%. The mass detection limit for cadmium is 3 fmol, the lowest mass detection limit hitherto reported for any electroanalytical technique. The measurements are based on the principle of constant current stripping potentiometry. Amalgamated analytes are re‐oxidized by a Combination of an applied constant current and spontaneous chemical oxidation. Equations making it possible to apply Coulomb's law are presente

ISSN:1040-0397    

DOI:10.1002/elan.1140070703

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractFour glucose sensors have been developed by modifying carbon paste electrodes with glucose oxidase as a biocomponent and a conducting redox osmium‐polymer as the mediating compound. The enzyme was immobilized by crosslinking with glutaraldehyde and bovine serum albumin in three modifications of electrodes and physical adsorption in one electrode. The optimal concentrations of the modifying compounds were determined and the response of the sensors to 2–20 mM glucose were characterized. The influence of pH, temperature, interferences, and storage on the responses of the sensors were investiga

ISSN:1040-0397    

DOI:10.1002/elan.1140070704

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractSmall inexpensive soil water sensors and the necessary electronics package for fast voltammetry (l04V/s scan rate) are described. The sensor consists of a blunt ended hypodermic needle cathode containing a concentric PTFE insulating tube and therein, a Pt‐wire anode. The sensing film is formed by dip‐coating a 1:7 blend of a perfluorosulfonate and a polyestersulfonate polymer at the tip of the needle. Atop this sensing film is a composite protective film of cellulose acetate and nylon that inhibits the passage of ionic or low MW constituents and allows the transport of water. The sensor is sheathed in a PTFE tube that protrudes beyond the sensor tip and the protrusion gap is filled with a paste of talc and BaSO4which serves as a water conduit between the soil and the sensor proper. The sensor is capable of making reliable moisture measurements between the wilting point and the field capacity of the soil sample; the response behavior consists of the combination of two nearly linear segments, the sensor output increasing steeply between the wilting point and ca. 60% of the field capacity and then much more gradually to the field capacity. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several mon

ISSN:1040-0397    

DOI:10.1002/elan.1140070705

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractNeutral (or under‐oxidized) PPY film electrodes were directly prepared by electropolymerization and elimination of the subsequent oxidation of the deposited PPY layers during the polymerization process. Electroactivity and selectivity could be established on these nonconducting, densely packed neutral PPY film electrodes through controlled oxidation. Development of electroactivity for different redox solutes was concluded to be a combination of the creation of conducting areas and the opening of transport channels in the neutral PPY network by the oxidation. Selectivity of the PPY film electrode was controlled by selection of electrolyte counter‐anion, management of molecular size, and change of

ISSN:1040-0397    

DOI:10.1002/elan.1140070706

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractA novel approach for chemical modification of carbon paste electrodes (CPEs) has been investigated. Selected water‐insoluble inorganic salts as modifiers were found to exhibit preconcentration capability for oxalic acid under open‐circuit conditions in a pH 4.3 buffered solution. After medium exchange to a pure electrolyte (Britton–Robinson buffer, pH 8), the accumulated oxalate was measured by square‐wave anodic stripping voltammetry with a peak current response at 1.2 V (vs. Ag/AgCl). The water‐insoluble inorganic salts as modifiers were active through the interfacial accumulation of insoluble oxalate by the exchange of anions. The candidate inorganic salts should be, therefore, less insoluble than the corresponding oxalates, whereas, the differences in solubility between the modifiers and the corresponding oxalates are of minor importance. Among the investigated inorganic salts, lead sulfate produced the highest response under the employed conditions and was therefore exploited as accumulating material for oxalic acid. With suitable preconcentration times, a linear calibration graph from 0.7 mg/L to 42.8 mg/L of oxalic acid in the analyte solution was obtained, and a detection limit of 0.3 mg/L at a preconcentration time of 5min was achieved. The lead sulfate‐modified CPE was used to determine oxalic acid in orange juice without pre

ISSN:1040-0397    

DOI:10.1002/elan.1140070707

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractThe possibility of applying adsorptive stripping voltammetry (AdSV) in dispersed media has been evaluated. Sensitive methods for the determination of the herbicide terbutryn at nanomolar levels by AdSV at the hanging mercury drop electrode in micellar and emulsified media are proposed. The anionic surfactant sodium pentanesulfonate was chosen as the most suitable agent for micellar solutions and oil–water emulsions. On the other hand, ethyl acetate was used as the organic solvent to form terbutryn emulsions. A systematic study of the various experimental parameters that affect the stripping response was carried out by differential pulse voltammetry. When working in a 0.1 mol L−lperchloric acid medium with an accumulation potential of −0.60 V, terbutryn could be determined over the 6.0 × 10−9−4.0 × 10−7and 6.0 × 10−9−2.0 × 10−7mol L−1ranges in micellar (50s accumulation time) and emulsified (70s accumulation time) media, respectively. The limits of detection were 2.2 × 10−9and 1.1 × 10−9× mol L−1, and the relative standard deviations (n= 10) were 6.3 and 4.3% in micellar and emulsified media, respectively. The effect of other coexisting herbicides on the terbutryn stripping peak was evaluated. Finally, the developed method in emulsified medium was applied to the determination o

ISSN:1040-0397    

DOI:10.1002/elan.1140070708

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractAn amperometric biosensor based on a Clark oxygen electrode coupled with a biocatalytic layer containing tyrosinase has been developed for measurement in nonaqueous solvents. Glass filter paper was soaked with the enzyme and fixed on top of the electrode by a dialysis membrane. Thiourea derivatives were detected in hexane by evaluating the decrease in the response towards phenol. This method was fast and highly sensitive with detection limits in the range of 13–181 nM depending on the structure of the inhibitor compounds. The response time was up to 10min and depended on the inhibitor's structure. The mechanism of inhibition is discussed using kinetic parameter

ISSN:1040-0397    

DOI:10.1002/elan.1140070709

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractInfluences of a nonionic detergent Triton X‐100 on square‐wave voltammetry and anodic stripping square‐wave voltammetry of Cd2+in 0.5 M NaClO4+ 0.01 M HClO4are measured at precisely controlled durations of adsorptive accumulation and surfactant concentrations. Diagnostic criteria for the presence of surface‐active substances in electrolytes are reported. A voltammetric method for the quantitative analysis of detergents is proposed. An ionic type of detergent can be recognized by the variation of the accumulation po

ISSN:1040-0397    

DOI:10.1002/elan.1140070710

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY

摘要:

AbstractFlow injection analysis (FIA) systems incorporating potentiometric sensors for harmine and harmaline hallucinogens are described. The sensors are based on the use of harmine and harmaline tetraphenylborate or reineckate as electroactive compounds dispersed in plasticized PVC matrix. Laboratory‐build flow‐through sandwich cell equipped with silver disk coated with the sensing material is used as a detector in a low dispersion FIA system. The detector exhibits fast and linear response over the concentration range 10−2−10−6M harmine or harmaline with a detection limit of 2 μg/mL (for 100 μL samples). Operational pH ranges from 3 to 8, sampling rate is 80 per hour and the precision is typically ±0.6%. Recovery and reproducibility data agree fairly well with those obtained by gas–liquid

ISSN:1040-0397    

DOI:10.1002/elan.1140070711

出版商:VCH Verlagsgesellschaft mbH    

年代:1995

数据来源: WILEY