摘要:

An enzyme electrode was constructed from an oxygen electrode and a layer incorporating four enzyme systems for the sensitive determination of ADP and ATP. The cofactor is cycled between pyruvate kinase and hexokinase under formation of pyruvate which is detected by the coimmobilized, sequentially acting enzymes lactate dehydrogenase and lactate monooxygenase. The enzymatic recycling results in a 220-fold increased sensitivity to ADP compared to the unamplified reaction.

ISSN:0003-2719    

DOI:10.1080/00032718708062919

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Glassy carbon electrodes polished with some ceramics particles(TiB2SiC and TiC) show activation for the oxidation and reduction of catechol and hydroquinone. The activation was found to depend on the hardness of glassy carbon and ceramic particles.

ISSN:0003-2719    

DOI:10.1080/00032718708062920

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A colorimetric method for determination of phenols in water has been developed. The method, which is a modification of Liebermann's reaction, uses resorcinol as a chromogenic agent. The developed method is more sensitive, and the difficulties encountered in the widely used 4-aminoantipyrine method have been avoided. Application of both the proposed and 4-aminoantipyrine methods to the analysis of natural and tap water samples are presented.

ISSN:0003-2719    

DOI:10.1080/00032718708062921

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

N-Phenylcinnamohydroxamic acid, PCHA, was found to react with iron (III) to form complex species of different colour depending upon the reaction environment. The reaction conditions for the formation of the complex species were studied in aqueous-ethanolic medium. The general spectral properties of the species were investigated. The absorption curves were found to have two isobestic points. The number and composition of the complexes were determined and found to have composition 1:1, 1:2, 1:3 (Fe: PCHA). The wavelengths of the maximum absorbances were figured out to be 535, 495, and 445 nm for the I, II, and III complex species, respectively. It was verified that the Beer's law holds for these complexes at all wavelengths, and for the mixtures at the wavelengths of the isobestic points in a wide range of pH. The stepwise stability constants have been determined by the method of isobestic point and found to be log K1= 11.55, log K2= 10.11, and log Kg3= 7.44 for the I, II, and III complex species, respectively. The distribution diagrams (nomograms) of the complex species as a function of pH were constructed and the molar extinction coefficients of the three consecutive complexes have also been determined.

ISSN:0003-2719    

DOI:10.1080/00032718708062922

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The use of fluorescence detected circular dichroism (FDCD) for monitoring the quenching of chiral molecules is described. This technique combines the specificity for chiral centers of circular dichroism (CD), the sensitivity and selectivity of the fluorescence measurement with the additional chemical information provided by fluorescence quenching. Spectra are acquired using a multidimensional FDCD spectrometer which obtains a FDCD matrix of spectral data as a function of multiple excitation wavelengths (CD information) and multiple fluorescence emission wavelengths. This combination of FDCD and fluorescence quenching produces a very selective monitor for chiral fluorophores.

ISSN:0003-2719    

DOI:10.1080/00032718708062923

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

1-Naphthyldiphenylphosphine (NDPP), 9-anthryldiphenylphosphine (ADPP) and diphenyl-1-pyrenylphosphine (DPPP) and their oxides were prepared from triphenyl-phosphine (TPP) and the corresponding aryl bromides. These phosphines had no fluorescence, but their oxides showed blue fluorescence. The order of fluorescence intensities of these oxides were DPPP oxide > ADPP oxide > NDPP oxide. Hydroperoxides oxidized these phosphines to the corresponding oxides quantitatively. The relative reactivities were TPP > NDPP > DPPP > ADPP. The phosphines were stable in the dark, however, unstable in the light in chloroform. The reaction is proposed as novel type of fluorometry for hydroperoxides.

ISSN:0003-2719    

DOI:10.1080/00032718708062924

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The colour reaction between o-hydroxyhydroquinonephthalein and vanadate ion in the presence of hexadecyltri-methylammonium chloride and L-ascorbic acid as a reductant was discussed. And the spectrophotometric determination of vanadium utilizing the colour reaction system in micellar media was proposed at about pH 5.4. Beer's law was obeyed in the concentration range 0-8 μg of vanadium at 540 nm. The apparent molar extinction was 8.7 × 1041 mol−1cm−1with Sandell sensitivity of 0.0006 μg/cm2. This proposed method was relatively simple and sensitive, and then its applications for the waste water, river water, rain water, etc. were discussed.

ISSN:0003-2719    

DOI:10.1080/00032718708062925

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Injection of Benzo(a)pyrene into rats results in urinary excretion of fluorescent metabolites of BaP. The synchronous fluorescence (SF) technique can detect picogram quantities of fluorescent compounds such as 7,8,9,10-tetrahydro-tetrahydroxy-benzo(a)pyrene (BPT). BPT was used as a model compound to show that SF can detect 0.1μM of polynuclear aromatic compounds (PNA) or PNA metabolites in urine by simple dilution. The relatively high concentration limit is due to the need to dilute the urine 100 fold before the characteristic pyrenyl spectrum is observed. The upper limit of direct quantification of BPT without dilution of whole urine is 5μM because of urine quenching effects. A 100-fold dilution of urine, containing added BPT, restores normal fluorescence and SF spectra. The 0.1 μM detection limit is lower than the observed amounts of individual PNA in nonexposed, nonsmoking humans. This approach may provide a simple, noninvasive tool for monitoring human exposure to fluorescent toxic substances.

ISSN:0003-2719    

DOI:10.1080/00032718708062926

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A spectrophotometric method for the determination of carbafuran residues in field water using eerie sulphate as a reagent has been worked out.

ISSN:0003-2719    

DOI:10.1080/00032718708062927

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An amperometric procedure is described for the determination of glycerol and triglycerides in aqueous samples and in serum using glycerol dehydrogenase immobilized on a collagen membrane. Glycerol is determined by measurement of the steady-state oxidation currents generated at a platinum electrode by NADH produced in the enzyme-catalyzed reaction. The triglycerides were first hydrolyzed by the enzyme lipase in solution and the resulting glycerol determined similarly. Olive oil, determined to contain 78 % triolein, was used as the source of triglycerides in this study. For both glycerol and triglycerides the calibration plots are linear in the range from 0 to 12 μM, with detection limits of 0.2 and 0.7 μM, respectively. The immobilized glycerol dehydrogenase retained high operational activity for a period longer than 30 days.

ISSN:0003-2719    

DOI:10.1080/00032718708062928

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor