摘要:

A coated graphite-epoxy iron(III) ion-selective electrode, based on the ion-pair between [Fe(oxalate)3]3−anion and tricaprylylmethylammonium cation (Aliquat 336) in a poly(vinylchloride) (PVC) matrix is constructed. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) in PVC was deposited directly onto a PerspexRtube containing a graphite-epoxy conductor substrate attached to the end of a glass tube. The effect of membrane composition (ion pair, DBPh and PVC), oxalate concentration, pH and some cations and anions upon the electrode response is investigated. The electrode shows a linear anionic response to E vs. log[Fe3+] in the iron(III) concentration range from 2.9×10−6to 10−2mol/L, and a slope of −18.7±0.5 mV/dec, at pH working range 2-8 and 0.3 mol/L oxalate concentration. Variation in the potential of about ±2 mV was observed during a working day of 7-8 h. The response time was less than 5 sec and the lifetime of this electrode was superior to one year (over 1500 determinations by each polymeric membrane), with a practical detection limit of 2.1×10−6mol/L. Application of this electrode for iron(III) determination in biotônico sample (Brazilian tonic formula) is described.

ISSN:0003-2719    

DOI:10.1080/00032719708001791

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The reaction in organic solvent between atrazine and anti-atrazine antibody modified with 2,4-bis(o-methoxy-polyethylene glycol)-6-chloro-s-triazine was reported. Modification with activated PEG2 (2,4-bis(o-methoxypolyethylene glycol)-6-chloro-s-triazine) was demonstrated to have no influence on the binding affinity of the antibody. Solubility of the antibody modified with activated PEG2 in toluene was 26 μg/mL. PEG modified anti-atrazine antibody immobilized onto Controlled Pore Glass (CPG) was suggested to have affinity towards atrazine in the organic solvent and the possibility of application for the enzyme immunoassay was suggested.

ISSN:0003-2719    

DOI:10.1080/00032719708001792

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new system for the detection of triazine herbicide was prepared using the molecular imprinting approach. This method is based on the competition between fluorescent-labeled and the unlabeled substance-analyte for the specific binding sites, that were produced in polymer by the imprinting of the template. Polymer synthesis consists of radical polymerization of functional monomer (diethylaminoethyl methacrylate or methacrylic acid) and cross – linker (ethylene glycol dimethacrylate) in the presence of triazine as a template. After grinding of the polymer block and splitting off the template molecules a suspension of the polymer was used for the herbicide-specific sensor system. Selective detection of triazine in the concentration range of 0.01-100 mM was achieved within 4 hours.

ISSN:0003-2719    

DOI:10.1080/00032719708001793

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An attempt was made to develop hexafluorotantalate(V)-selective coated graphite electrodes based on Malachite Green, Crystal Violet, and Ethyl Violet using 1-chloronaphthalene, tri-n-butyl phosphate, and dimethyl phthalate as plasticizers. The electrode prepared by coating Malachite Green-hexafluorotantalate(V) extract in 1-chloronaphthalene with a PVC matrix on a graphite rod was found to give a Nernstian response to hexafluorotantalate(V) in a wide concentration range. Potential measurements with the coated graphite electrode were made against a plastic sleeve HF-resistant Ag/AgCl external reference electrode. Optimum response of the electrode was observed in test solutions made 1 mol/L in both sulphuric and hydrofluoric acids. The concentration range, slope, and detection limit from the plot of E vs log [Ta(V)] were found to be 1.0 × 10−5– 1.0 × 10−2mol/L tantalum(V), 58.0 ± 1.5 mV/decade, and 3.98 × 10−6mol/L tantalum(V), respectively. The relative standard deviation for six determinations of 5 × 10−4mol/L tantalum(V) was estimated to be 2%. The response time of the electrode was found to be 5-15 s and the electrode functioned properly for three months. The effects of diverse ions on the electrode response to hexafluoro-tantalate(V) were studied, and the potentiometric selectivity coefficients were evaluated. The electrode was found to be highly selective to hexafluorotantalate(V) and free from interference of niobium which commonly occurs with tantalum. The analytical application of the electrode was extended to the determination of tantalum in tantalite-columbite ores and several synthetic matrices using four potentiometric techniques and the results were in good agreement with the actual or certified values.

ISSN:0003-2719    

DOI:10.1080/00032719708001794

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Chloranilate PVC matrix membrane electrodes have been developed. These are based on the use of aliquat-chloranilate ion pair in plasticized PVC matrices. The calibration slope is about 60 mV/decade. The limit of detection is about 10−5M, the working pH range is 5-10, the electrodes have been used in the determination of lead, mercury, and cadmium ions with chloranilic acid, separately and in binary mixtures. 2-Nitro phenyl octyl ether, 2- nitro phenyl phenyl ether, dioctyl phthalate, dioctylsebacate, dioctyl phenyl phosphonate plasticizers are used; there were no significant differences in the performance characteristics of membranes for the various plasticizers. The life time of the electrodes is greater than one month.

ISSN:0003-2719    

DOI:10.1080/00032719708001795

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An amino acid biosensor based on the immobilization of L-or D-amino acid oxidase within an iridium-dispersed carbon paste electrode is described. The strong and preferential electrocatalytic activity of iridium towards hydrogen peroxide allows rapid measurements of amino acids at very low potentials where the possibilities of interferences are minimal. The detection limits, depending on the amino acid, are in the order of 10−5M. The influence of parameters such as flow rate, working potential, iridium and enzyme loadings are discussed.

ISSN:0003-2719    

DOI:10.1080/00032719708001796

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Amperometric oxygen sensors employing non-platinum electrocatalyst made from pyrolyzed cobalt-tetramethoxy-phenylporphyrin (CoTMPP) are described. A technique for the preparation of an oxygen working electrode with catalyst from a pressed matrix (tablet) is presented. This technique allows manufacturing numerous electrodes from the same pressed tablet, all of which demonstrate good reproducibility of their parameters. Glucose biosensors are constructed using this oxygen electrode as a basic transducer for amperometric detection of oxygen consumption. The enzyme (glucose oxidase) is held in a micro-bioreactor (face side closed by a Silastic coated polycarbonate membrane) in which the oxygen sensor is immersed. Linearity of the sensor response to glucose concentrations up to 16 mM is reported. Sensors demonstrated a stable signal (varying within ±5% of its average value) during 15 days of continuousin vitroglucose monitoring at 37°C.

ISSN:0003-2719    

DOI:10.1080/00032719708001797

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An amperometric immunosensor for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water has been developed using sequential injection analysis techniques. The system is based on a rapid competitive enzyme immunoassay employing an alkaline phosphatase-labeled monoclonal antibody directed against the herbicide and an immunoreactor with 2,4-D immobilized via bovine serum albumin either to Eupergit in a column or directly to the surface of a glass capillary. The detection limit of the immunosensor at 0.1 μg 2,4-D/l without enrichment of the analyte makes automatic measurements of 2,4-D in drinking and ground water feasible.

ISSN:0003-2719    

DOI:10.1080/00032719708001798

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A method for the determination of nucleic acids with methylene blue(MB) as a fluorescence probe was developed, based on the quenching of the fluorescence of MB in the presence of nucleic acids. The calibration graph was linear in the range of 0–40 μg/ml for CT DNA and 0–55 μg/ml for yeast RNA, the limit of detection was 28 ng/ml for CT DNA and 82 ng/ml for yeast RNA. CT DNA could be determined in the presence of 30%(w/w) yeast RNA and yeast RNA was determined when the content of CT DNA in synthetic samples was below 5%(w/w).

ISSN:0003-2719    

DOI:10.1080/00032719708001799

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A method for the enzymatic determination of adenosine triphosphate (ATP) and glycerol has been developed, using an automated FIA system. The enzymes Glycerophosphate Oxidase (GPO) and Glycerol Kinase (GK) have been immobilized on non-porous glass beads following optimization of the immobilization parameters. The fabricated Single Bead String Reactors (SBSR) were used in connection with a FIA system, following optimization of its parameters. The half-life of GK SBSR, regarding enzyme activity, was found to be 45 days for 90 measurements of daily use and storage at 4°C in the appropriate buffer. The linear dynamic ranges of the working curves for the enzymatic determinations of ATP and Glycerol, were 4–70 μmol.l−1and 2–160 μmol.l−1respectively. Glycerol was determined in white and red wines after a 1:5,100 dilution. Glycerol was also determined in human serum, following deproteinization of the samples by gel filtration. The low limits of quantification (4μmol.l−1ATP and 1 μmol.l−1glycerol) and accuracies better than 2% for ATP and 1% for glycerol, show that the proposed method offers many significant improvements over the conventional methods.

ISSN:0003-2719    

DOI:10.1080/00032719708001800

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor