摘要:

A novel and sensitive method for the enzymatic determination of trace amount of mercury ion based on its inhibitory action on urease is proposed. Mercury(II) inhibits the urease-catalysed urea hydrolysis by binding with sulphydryl groups of urease. The inhibited enzymatic reaction is monitored in-situ with a SAW/impedance enzyme transducer which is composed of a SAW resonator oscillating at 61 MHz and a pair of parallel electrodes. The inhibition mechanism of Hg(II) on urease is discussed. The kinetic parameters and inhibition parameters are estimated. The frequency response of the transducer is proportional to mercury concentration over the range of 50-350 ng/mL. The detection limit is 20 ng/mL. The relative standard deviation was 2.9% for six measurements of 150 ng/mL Hg(II). The effect of potential major interferences was investigated. The method was successfully applied to the determination of Hg(II) in waste water and the results obtained by proposed methods compared well with those obtained by atomic-absorption method.

ISSN:0003-2719    

DOI:10.1080/00032719508006398

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An amperometric enzyme electrode for the determination of glucose (<16mmol−1) is constructed by incorporating electron mediators tetrathiafulvalene in Nafion and subsequently coating with immobilized glucose oxidase. The results obtained from measurements of glucose in fermentation samples containing biomass or molasses indicate the utility of the electrode for glucose assay in such media over at least 12 weeks. Digital simulation is employed to study the cyclic voltammetry (CV) of Tetrathiafulvalene-Glucose Oxidase-Modified Glassy Carbon Electrode (TTF-GOD-GCE); the digital model is built and the effects of kinetic parameters on CV-curves are discussed. The response process of the Tetrathiafulvalene-Glucose Oxidase-Modified Electrode is partly explained by the simulation results and further research is expected to guide the design of biosensors and improve the properties of the enzyme-mediator modified electrode.

ISSN:0003-2719    

DOI:10.1080/00032719508006399

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The features of a biosensor based on a platinum electrode modified with a poly(phenol) film coupled with two enzymes, alkaline phosphatase(AP) and glucose oxidase(GOD), were studied. The modification of the surface of the working electrode decreases interference from ascorbic acid, uric acid and some oxidizable organic materials (e.g. glycine), and decreases the noise of the current. The concentration of substrate, the activity ratio of the two enzymes, the applied potential, and the assembling of biosensor are important for the determination of low levels of phosphate.

ISSN:0003-2719    

DOI:10.1080/00032719508006400

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Detection of ricin, in a piezoelectric quartz crystal microbalance format, can be accomplished with the use of capture antibody techniques. These techniques allow for the specific attachment of ricin to immobilized capture antibodies on the quartz crystal transducer area. A reversed format can also be used to detect antibody in solution. In this case, the antigen is immobilized and antibody attaches specifically, thus increasing the overall mass and decreasing the resonant frequency. In this report we describe detection of both ricin and anti-ricin antibody using immunological piezoelectric quartz crystal microbalance techniques.

ISSN:0003-2719    

DOI:10.1080/00032719508006401

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The authors present a simple liquid chromatographic method which enables direct separation of S(+) and R(−) oxazepam glucuronides and free oxazepam as well as diazepam (internal standard) in a single run. Metabolites and oxazepam are quantified by direct injection of diluted urine. Application to the study of urinary excretion in sheep revealed a S/R ratio of 6.37 which is one of the highest ever observed among various animal species. The percentage eliminated as refered to administrated oxazepam was found to be near 35% which is particularly low compared to other species (60 to 80%).

ISSN:0003-2719    

DOI:10.1080/00032719508006402

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The stopped-flow mixing technique was used to develop an automated room-temperature liquid phosphorimetric method for the straightforward, fast determination of naproxen in serum samples. The interaction of naproxen with thallium(I) ions in the presence of sodium dodecyl sulfate allows one to obtain a kinetic curve that levels off within only 2 s. This approach allows the development of very fast kinetic and equilibrium methods by using the slope and amplitude of the kinetic curve, which are directly proportional to the naproxen concentration, as analytical parameters. The linear calibration range thus achieved is 0.06-15 or 0.08-15 μg mL−1, depending on wheather slope or amplitude measurements are used. The within- and between-assay precision data, as well as the selectivity of the method are more than adequate for the determination of naproxen in serum samples pretreated with acetonitrile. Analytical recoveries range from 90.7 to 104.0%.

ISSN:0003-2719    

DOI:10.1080/00032719508006403

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A simple, fast analytical procedure is reported for the determination of vitamin C in a cottage-cheese dessert. The method was developed on the basis of the bromate ion — iodide ion — ascorbic acid clock reaction. The results of three different variants of the quantitation are discussed in detail.

ISSN:0003-2719    

DOI:10.1080/00032719508006404

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Two spectrophotometric methods involve the formation of two different ion pairs between the drug and inorganic complexes, Mo(V) and Co(II) thiocyanates followed by their extraction with dichlorømethane and o-nitrotoluene, respectively. The optimum conditions for the ion pair formation are established. The methods permit the determination of metoclopramide and oxybuprocaine hydrochlorides over a concentration range of 1-20 μg ml−1and 20–240 μg ml−1using Mo(V) and Co(II) thiocyanates, respectively. Molar ratio of drug to Mo(V) or Co(II) indicates a 2:1 ratio for the two drugs studied in the presence of excess thiocyanate concentration. Results of the analysis of drug substances and their dosage forms by the proposed methods are in good agreement with those obtained by the official methods.

ISSN:0003-2719    

DOI:10.1080/00032719508006405

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We developed three methods for the simultaneous determination of amiloride (AMI) and hydrochlorothiazide (HCT): zero-crossing, derivative quotient spectra with normalized divisor and multiple linear regression (MULTIC) methods. The two first methods use the derivative spectrophotometry, and the last one uses the absorbance measurement. The three methods were used to determine both compounds in synthetic mixtures and pharmaceutical preparations with errors less than 5% and 15%, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719508006406

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An improved method with derivatization and gas chromatography (GC) is described for the determination of captopril, an antihypertensive agent. The method is based on the derivatization of captopril with pentafluorobenzyl bromide in acetonitrile, using potassium carbonate as a base catalyst. Under a mild condition, the highly polar and nonvolatile captopril was derivatized into a derivative with suitable chromatographic properties. The resulting derivative was separated on an OV-1 column and monitored with a flame-ionization detector (FID). The linear range of the method for the determination of captopril was over 0.25-4.00 μmol. The detection limit (signal-to-noise ratio = 3) of captopril was about 40 nmol. The method was satisfactorily applied to the analysis of captopril in tablets.

ISSN:0003-2719    

DOI:10.1080/00032719508006407

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor