摘要:

Biosensing of hydrogen peroxide was made at a carbon paste electrode incorporating fumed silica, horseradish peroxidase and N-methyl phenazine methosulphate. Cyclic voltammetric and amperometric measurements were used for the first time to demonstrate the suitability of electron communication between horseradish peroxidase and a carbon paste electrode via N-methyl phenazine methosulphate, an electron transfer mediator. Performance and characteristics of the biosensor were evaluated with respect to response time, detection limit, applied potential and concentration of the mediator. Effect of applied potential and amount of the mediator in carbon paste on the Michaelis-Menten constant of the biosensor was investigated. The biosensor possessed a variety of characteristics including long stability and rapid response and high sensitivity to hydrogen peroxide, with a detection limit of 0.08 μM.

ISSN:0003-2719    

DOI:10.1080/00032719708002797

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper describes a new optical chemical sensor based on 1,4-bis(1,3-benzoxazoly-2)benzene(BBOB) as a sensing material. The sensing membrane incorporating BBOB is able to selectively extract ethacrynic acid (EA) from the sample solution into the organic membrane phase, and reversibly forms a 1:1 complex. This process resulted in a change in fluorescence signal. The optimized sensing membrane could be used for the determination of EA from 8.0 × 10−2mol·L−1to 1.0 × 10−4mol·L−1. Besides the high reproducibility of the optical signals, very short response times of less than 30s were achieved. The optrode membrane was successfully applied to the determination of EA in commercial tablets. The results showed a good agreement with those obtained by the pharmacopoeia method.

ISSN:0003-2719    

DOI:10.1080/00032719708002798

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Previously purified cytochrome c can exhibit a current response at a silver electrode and the electron transfer reaction can be promoted by dodecyl benzene sodium sulfonate. Addition of the promoter to the protein solution, the peak potentials of the protein are unchanged, but the peak currents increase sharply. Experimental results reveal that the peak current is linearly proportional to the protein concentration in the range of 0.08 – 1.2 μmol/L. The detection limit is 0.05 μmol/L. In addition, commercial samples as received can also give good redox waves after the macromolecules are acted on by the promoter. So the current response of the protein can be widely used.

ISSN:0003-2719    

DOI:10.1080/00032719708002799

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An in situ photochemical fluorescence probe method for the determination of nucleic acids with vitamin k3(VK3) as the photochemical fluorescence probe was developed for the first time. It was based on the conversion of VK3into an intensively fluorescent product on irradiating with UV radiation. The photochemical reaction is decelerated by nucleic acids. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range of 0– 1.5 μg/ml for CT DNA and 0–2.0μg/ml for yeast RNA, the limit of detection was 10 ng/ml for CT DNA and 26 ng/ml for yeast RNA. The kinetic behaviour of the photochemical reaction and the effects of some experimental conditions were investigated and discussed in detail. CT DNA could be determined in the presence of 40%(w/w) yeast RNA and yeast RNA was determined when the content of CT DNA in synthetic samples was below 6%(w/w).

ISSN:0003-2719    

DOI:10.1080/00032719708002800

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Based on collecting trace aniline on a membrane filter and dissolving the filter in an organic solvent, a simple and rapid preconcentration technique has been proposed for its spectrophotometric determination in water samples. In 0.1M of hydrochloric acid medium, aniline diazotizes with nitrous acid, which is then coupled with N-(1-naphthyl)-ethylenediamine at the same acidity. The azo-dye formed is collected on a 0.45μm nitrocellulose filter at pH 5.0 of acetate buffer solution in the presence of surfactant tetradecylpyridinium chloride. The dye with the filter is dissolved in a small volume of 2-methoxyethanol acidified with hydrochloric acid, and the absorbance of the resulting solution is measured at 560 nm against a reagent blank. Detection limits better than 1.0μg · L−1of C6H5NH2can be achieved. The components normally present in water do not interfere when a masking agent solution is added. The proposed method has been applied to the analysis of water samples from several sources. The recoveries of the aniline added to the samples are quantitative, and results found are satisfactory.

ISSN:0003-2719    

DOI:10.1080/00032719708002801

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This work shows that diffuse reflectance measurements, using fiber optical devices, can give rapid quantitative results for application with spot tests determination where little sample manipulation is a desirable feature. The experiments were performed with a Hewlett Packard diode array spectrophotometer HP8452A and a Labsphere RSA-HP-84 reflectance accessory. The quantitative reflectance measurements of different complexes such as Fe (III) with thiocyanate, Cr (VI) with diphenylcarbazide and Ni (II) with dimethylglyoxime could be obtained by forming the complexes on filter paper. Calibration curves were obtained for each metal by plotting the optical density of the reflectance signal (AR) vs. the log of the mol/dm3concentration, from 1.5 × 103to 3.6 × 102mol/dm3for Fe (III), from 8.00 × 10−5to 2.00 × 103mol/dm3for Cr (VI) and from 1.00 × 103to 8.00 × 102mol dm3for Ni (II), with correlation coefficients of 0.9986 for Fe (III), 0.9878 for Cr (VI) and 0.9892 for Ni (II). The results obtained show that it is possible to perform quantitative spot-test analysis using reflectance measurements in the visible region of the spectrum.

ISSN:0003-2719    

DOI:10.1080/00032719708002802

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Determination of nickel has been carried out by electrothermal atomization atomic absorption spectrometry (ETAAS) using unpyrocoated tubes. A generalized method has been developed for quantitative determination of total nickel in different types of samples: geological, like rock, soil and sediment, environmental, like sewage sludge, and biological, like mussel tissue and rice flour, after their rapid microwave-assisted digestion. The systematic study of the effect of six different matrix modifiers demonstrated that, using an ashing temperature of 1000°C and carrying out the atomization at 2700°C, neither modifier nor background correction are necessaries. The recommended procedure is based on the pressurized acid digestion of samples with aqua regia, HF and H2O2, in different steps, inside hermetically closed teflon reactors, heated by radiation in a microwave oven, at power levels between 330 and 550W. After the complete dissolution of samples, Ni is determined by ETAAS carrying out the absorbance measurements in the peak height mode, and using aqueous solutions of Ni as standards.

ISSN:0003-2719    

DOI:10.1080/00032719708002803

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The optimum conditions for the formation of an ion-associate between chlorochromate ion and Neotetrazolium chloride (NTC) were found. The molar ratioNTC:Crin the extracted ion-associate was found to be 1:2. Beer's law was obeyed in the range 0.05 – 1.5 μg ml−1Cr(VI). The molar absorptivity determined at 255 nm, was 3.12±0.06 × 104L mol−1cm−1. The method was used for determination of chromium in steels, various types of soils and plants.

ISSN:0003-2719    

DOI:10.1080/00032719708002804

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The application of derivative spectrophotometry to the simultaneous determination of nickel(II) and mercury(II) with diethylenetriaminepentaacetic acid (DTPA) is described. The procedure doesn't require equations to be solved, and it is suitable for concentrations of 0.40–1.80 mg ml−1of nickel and 0.20–0.70 mg ml−1of mercury. The main interferences, both anionic and cationic, are easily eliminated. The method was applied to different aqueous matrices and it was compared with an atomic absorption (AA) method. Good results were obtained.

ISSN:0003-2719    

DOI:10.1080/00032719708002805

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Silver has a very strong catalytic effect on the peroxodisulphate oxidation of Brilliant Cresyl Blue in the presence of 1.10-Phenanthroline as an activator. The reaction was followed spectrophotometrically by measuring the rate of change in absorbance of brilliant cresyl blue at 635 nm and 30°C. Silver can be determined in the range of 0.3 – 1500.0 ng/ml by a fixed time method. The limit of detection is about 0.1 ng/ml of silver. Silver in real samples was determined with satisfactory results.

ISSN:0003-2719    

DOI:10.1080/00032719708002806

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor