摘要:

A new in-situ photochemical kinetic fluorimetric method was proposed for the determination of biacetyl (BI). It is based on the sensitization of BI on the photochemical reaction of amaranth (AM). AM, a nonfluorescent compound was converted into an intensively fluorescent compound in a slightly alkaline medium by the sensitized photochemical reaction, and BI was indirectly determined by monitoring the change of the fluorescence intensity. The determination can be carried out by fixed-time method or tangent method. The kinetic behavior of the reaction and the effects of some experimental conditions were investigated and discussed. The calibration graph was rectilinear from 1.0 μg ml−1to 10.0 μg ml−1of BI (r= 0.999), the limit of detection was 1.0 ng ml−1, and the coefficient of variation was 0.44% for 0.90 μg ml−1of BI (n = 6). The mechanism for the sensitization of BI was examined and the triplet-triplet energy transfer, in which BI acted as the energy donor and AM as the energy acceptor, was suggested to be the main cause. Its application to real samples has been tested.

ISSN:0003-2719    

DOI:10.1080/00032719308021490

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In a solution containing 0.005M borax medium (PH= 8− 10). 0.03% ascorbic acid and 0.001% gelatin, a fine sensitive adsorptive reduction peak of manganese appeared at −1.53v (vs.SCE) on a hanging mercury electrode by fast speed scanning voltammetry. The derivative peak current is directly proportional to the concentration of manganese in the range from 1.0×10−8M to 2.0×10−6M. The detection limit is 3.0×10−9M. Using this method, we have successfuly determined tracesof Mn in water and strawberry samples.

ISSN:0003-2719    

DOI:10.1080/00032719308021491

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Heavy metals Zn, Cd, Pb, Cu, Ni and Co from two spanish river sediments have been determined by voltammetric techniques, along with % CaCO3and % organic matter, and the whole data set examined by means of Factor Analysis, finding a different behaviour of the metals in each river.

ISSN:0003-2719    

DOI:10.1080/00032719308021492

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ascorbic acid was determined indirectly by spectrophotometry at 666 nm based on the photochemical reduction of methylene blue using flow-injection analysis. The carrier stream was 12.7 μgml−1methylene blue in phthalate-HCl buffer solution at pH 3.2. The reactor was irradiated with a 500-Watt halogen lamp to facilitate the development of the photochemical reaction. The system allows determination of ascorbic acid in the range 0.18–6.12 μgml−1with relative standard deviations of 2.09 and 0.31% for 1.97 and 4.92 μgml−1samples, respectively, and a sampling frequency of 50–55 h−1. The proposed method was applied successfully to the determination of ascorbic acid in vitamin C tablets.

ISSN:0003-2719    

DOI:10.1080/00032719308021493

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method is described for the determination of fumonisin B1 in corn. The method involves sample extraction with methanol:water (75:25) and partial purification using a solid phase extraction. Fumonisin B1 is reacted with naphthalene-2,3-dicarboxaldehyde (NDA) to produce a highly fluorescent derivative, 1-cyano-2-alkyl-benz[f]isoindole (CBI) and then separated from the sample matrix on a reverse phase C-18 column with a mobile phase of acetonitrile:water:acetic acid (55:45:1). The NDA-derivative is quantitated by fluorescence detection at 410 nm excitation and a 440 nm, long past emission filter. Recoveries of fumonisin B1 added to corn at levels of 0.25–20.0 μg/g averaged 88.1% with a coefficient of variation of 10.3%. Confirmation of fumonisin B1 in corn samples was accomplished by fast atom bombardment (FAB) spectroscopy.

ISSN:0003-2719    

DOI:10.1080/00032719308021494

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A Kinetic-spectrophotometric method for the determination of ultra-trace amounts of osmium(VIII) is described. It is based on the catalytic action of osmium(VIII) on the oxidation of pyrogallol red with hydrogen peroxide, yielding a colorless product in neutral medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 540 nm and 30°C. Os(VIII) in the range 0.005 -100 ng.ml−1can be determined. The proposed method is hardly subject to interferences. The relative standard deviation is 1.5% for 1 ng.ml−1of Os(VIII). The kinetic parameters of the catalyzed and uncatalyzed reactions are reported. The detection limit is 1 pg.ml−1.

ISSN:0003-2719    

DOI:10.1080/00032719308021495

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Mixture Design and a Chromatographic Response Function were used to study the effect of different organic solvents as modifiers on the Reversed Phase (C-18) High Performance Thin Layer Chromatographic separation of three amino acid hydroxamates (Arginine hydroxamate, Threonine hydroxamate, and Histidine hydroxamate). Both 3 solvent (methanol, acetonitrile and tetrahydrofuran) and 4 solvent (methanol, acetonitrite, tetrahydrofuran and acetone) systems were studied.

ISSN:0003-2719    

DOI:10.1080/00032719308021496

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A 3-factor statistical mixture design and a 2-factor chromatographic response function were used in the solvent optimization of the RP-HPLC separation of a mixture containing free histidine, methionine, tyrosine, phenylalanine and tryptophan. The influences of phosphoric acid, methanol and acetonitrile on the separation were compared. A solvent condition resulting in a satisfactory separation of the amino acid mixture was predicted.

ISSN:0003-2719    

DOI:10.1080/00032719308021497

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0003-2719    

DOI:10.1080/00032719308021479

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor