摘要:

Based on the principle of enzyme inhibition, a novel and sensitive lipase biosensor to determine organophosphorus pesticide is presented. Contact of the enzyme with pesticide samples results in specific inhibition of enzyme activity. Sensor calibration was possible by correlating the inhibition of enzyme activity with various concentrations of pesticide compound in a buffer solution. The sensor was successfully used to determine pesticide concentrations ranging from a low of 167ng/ml to 1.34μg/ml, and the detection limit is 81ng/ml. The effects of temperature, pH value, incubation time and solvent were also investigated. The sensor was also applied to the determination of dimethoate residues in the peel and flesh of tomato.

ISSN:0003-2719    

DOI:10.1080/00032719708001811

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A manganese dioxide film modified carbon paste electrode was developed for use as an amperometric sensor for the determination of hydrogen peroxide (H2O2) in ammoniacal aqueous solutions. The electrode showed a stable response towards H2O2after electrochemical activation. Effects of flow rate, operating potential, concentration, injection volume and interferences were investigated. A linear response towards H2O2from 5 μg.l−1to 450 mg.l−1and a detection limit (3 signal-to-noise ratio) of 4.7 μg.l−1was found. The method was employed for the determination of H2O2in rain water samples.

ISSN:0003-2719    

DOI:10.1080/00032719708001812

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A novel reusable amperometric immunosensor was developed for the determination of cortisol by co-immobilizing horseradish peroxidase (POD) and cortisol-antibody on a chemically activated affinity membrane which is mounted over the tip of an oxygen electrode. The enzymatic electrocatalytic current response to the respective substrate is inhibited by the association of the antigen to the co-immobilized antibody. The sensor can be regenerated to facilitate several assays by washing with dilute hydrochloric acid solution. The advantages of the sensor include rapid-response, simple analysis methodology and high selectivity. The calibration curve for cortisol is linear in the concentration range of 1 × 10−7– 1 × 10−5M. The optimal conditions of immobilization and pH have been studied. The inhibition of enzymatic activity was confirmed by luminescence measurement utilizing the luminol- H2O2-POD system.

ISSN:0003-2719    

DOI:10.1080/00032719708001813

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

L-Histidine, a biologically important amino acid, has been modified onto the silver electrode through covalent bonding. The coenzyme dihydronicotinamide adenine dinucleotide (NAD(P)H) was electrocatalytically oxidized to NAD(P)+at a L-histidine modified silver electrode (His/Ag). The electrochemical processes at the His/Ag electrode were investigated by using UV-visible spectroelectrochemistry in detail. Amperometric determination of NAD(P)H, at a potential of 0.25V (SCE), gave a linear response in the range of 1 × 10−7∼2 × 10−5mol/L with a detection limit of 0.05 μmol/L. The His/Ag electrode has been used in a FIA system with satisfactory results. Meanwhile, other proteins and chemicals present in samples do not interfere in the assay.

ISSN:0003-2719    

DOI:10.1080/00032719708001814

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Recently affinity chromatography with a biospecific stationary phase was widely used in separation and purification processes of all kinds of enzymes. In this paper, a series of synthetic reactions of solid-liquid phase on a silica surface are described. By using a wide-pore (30μm). microspheric silica (8μm) as the matrix and γ-aminopropyltriethoxy-silane as the activating agent, the nicotinamide adenine dinucleotide (NAD) was bonded through its amino groups with carboxylic groups of linked phospholipid by a covalent bond on the aminated supports. This bonded stationary phase provided high thermal stability which could be used for separating nucleotides with good resolution. At the same time, the effects of pH, organic modifier and ionic strength on the retention properties of nucleotides were also investigated.

ISSN:0003-2719    

DOI:10.1080/00032719708001815

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two procedures for separation and determination of vitamin B12in multivitamin tablets by reversed phase high performance liquid chromatography are proposed. Sample preparation is very simple: tablets are dissolved in distilled water, centrifuged and filtered. The sample solution is directly applied in the sample loop injector and chromatograms are obtained with gradient elution using water-methanol and water-acetonitrile as solvents. The peak of vitamin B12from samples of B-complex tablets is well separated with the two procedures. For multivitamin tablets, however, only the procedure with water and methanol as solvents was good for separation and quantification of vitamin B12. Both procedures were verified by the standard addition method and also compared to a previously developed method using electrothermal atomic absorption spectrometry for vitamin B12determination.

ISSN:0003-2719    

DOI:10.1080/00032719708001816

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A simple flow-injection spectrophotometric method for the determination of thioridazine is described. The method is based on the oxidation of thioridazine with phosphotungstic acid in hydrochloric acidic media. Concentrations of thioridazine in the range 10 – 60 ppm are determined with a relative standard deviation of 1.1%. The method was applied to the determination of thioridazine in pharmaceutical formulations.

ISSN:0003-2719    

DOI:10.1080/00032719708001817

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two spectrophotometric methods have been developed for the determination of lignocaine in pure raw material or in formulated dosage form. One of these methods is based on the extraction of the ion-associate formed with reineckate salt by nitrobenzene or chloroform/acetone [solvent mixture, 1:1 (v/v)] and the absorbance is measured at 525 nm and at pH 5. Beer's law is obeyed in the range 0.2-2.0 mg/mL. The other method depends on the oxidation of lignocaine by Ce(IV), the excess of Ce(IV) is reacted with chromotrope 2B or chromotrope 2R where the red colour of the reagent decreases. The absorbance is measured at 510 and 530 nm and the methods are found useful in the concentration ranges 0.5-2.5 and 1.1-3.4 μg/mL, respectively. In another approach iron (II) is added to the excess Ce(IV) followed by the reaction with thiocyanate, salicylate or o-phenanthroline. The developed colours are measured at 450, 520 and 510 nm with concentration ranges 1.5-12.3, 1.8-10.6 and 0.5-4.3 μg/mL, respectively. It is evident that the use of the thiocyanate method is more preferable due to its wider usable concentration range.

ISSN:0003-2719    

DOI:10.1080/00032719708001818

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The possibility of using electroseparation methods with UV/Vis detection in the study of some β-agonist drugs has been investigated. Clenbuterol, Salbutamol and Terbutaline were separated and quantitatively analyzed in various drugs. The influence of several parameters, such as pH, temperature, surfactants, column type and electrical values were studied.

ISSN:0003-2719    

DOI:10.1080/00032719708001819

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Barbituric acid reacts with chloral hydrate in alkaline media, after heating for 1 min. at 100°C to give an orangish yellow colour having maximum absorbance at 450 nm. The reaction is selective for barbituric acid with 0.01 mg/ml as the visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's Law from 0.001 to 0.6 mg/ml and the relative standard deviation is 1.1%. The quantitative assessment of tolerable amounts of other drugs is also studied.

ISSN:0003-2719    

DOI:10.1080/00032719708001820

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor