摘要:

A sensitive catalytic kinetic spectrophotometric method for determining ng ml−1concentrations of selenium is described. The method, based on the catalytic effect of Se (IV) on the reduction of azureA by sulphide, is monitored spectrophotometrically at 600 nm. The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, free from many interferences and is widely applicable. The limit of detection is 2.5ng ml−1of Se. The relative standard deviation of seven determinations of 100 ng ml−1Se was 1.5%. The method was applied to the determination of selenium in spiked water, Kjeldahl tablets, synthetic samples and health care products.

ISSN:0003-2719    

DOI:10.1080/00032719908542870

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Terphenyl (TP) isomers p-terphenyl (p-TP) and m-terphenyl (m-TP) were studied by second-derivative solid-substrate room temperature phosphorescence (d2-SS-RTP) with thallous sulfate as a heavy atom perturber and filter paper as substrate. Various factors affecting d2-SS-RTP were discussed in detail. The method for the simultaneous determination of p-TP and m-TP was proposed without any preliminary separation.

ISSN:0003-2719    

DOI:10.1080/00032719908542871

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A sensitive method for the determination of trace copper by preconcentration and adsorption of its 1-nitroso-2-naphthol complex onto the microcrystalline benzophenone has been developed. Several experimental conditions such as the pH of the solution, the quantities of 1-nitroso-2-naphthol and benzophenone, and the stirring time were optimized for effective separation. Trace copper in a 100 ml water sample was chelated with 2.0 ml of 0.050 M 1-nitroso-2-naphthol at pH 8.0. The solution was heated to 30 °C, stirred vigorously for 10 minutes to adsorb the copper complex quantitatively onto 0.20 g benzophenone. After the microcrystalline benzophenone adsorbed copper complex was filtered and dissolved in acetone, the content of copper was determined by flame atomic absorption spectrophotometry. The interfering effects of concomitant ions were investigated and almost eliminated. The detection limit and the determination limit of this method were 6.9 ngml−1and 22.9 ngml−1, respectively. Recoveries of 103.7 % and 94.2 % were obtained in a tap water and a brass sample, respectively. In the determination of copper in real samples, the values obtained by this proposed method were close to those by GF-AAS.

ISSN:0003-2719    

DOI:10.1080/00032719908542872

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new method using microemulsified samples is presented. The method is suitable for the determination of manganese, present as methylcyclopentadienyl manganese tricarbonyl, in gasoline in the range 0∼75μg ml−1. The method has the advantage of simplicity, speed and the use of aqeous standards for calibration instead of organic standards. Coexistent elements do not disturb the determination. Results obtained by this method were better than those obtained by other methods for the same samples.

ISSN:0003-2719    

DOI:10.1080/00032719908542873

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A direct anion exchange ion chromatography (IC)-based method for the detection of the chemical warfare (CW) agent degradation product, O-isopropyl methylphosphonic acid (IMPA) in agar medium has been developed. This is the first report of the development and validation of an IC-based method for the analysis of IMPA in a microorganism and agar matrix. In these experiments, IMPA served as a surrogate for the CW agent GB (Sarin) in a development program for living micro-organism-based CW agent destruction systems. Petri dishes containing the medium with 10, 100 and 1000 μg/mL IMPA were used. Samples were prepared by dilution of the agar medium with deionized water followed by sonication and then filtration before the analysis by IC/conductivity detection. Using this method, the amount of IMPA in the Petri dishes was measured. Excellent separation efficiency and freedom from interference due to common anions such as chloride and sulfate was obtained in the developed method. Retention time precision was ⩽1.0% relative standard deviation (%RSD) and the detection limit was 0.1 μg/mL. Calibration curves using five IMPA concentrations over the range 1-100 μg/mL in blank agar matrices at three different dilutions (0-fold, 4-fold, and 40-fold diluted with reagent water) gave correlation coefficients (r2) of 0.997, 0.992, and 0.995, respectively. Using three different samples and IMPA spiked into the quenched agar matrix at three levels (10, 100, and 1000 μg/mL), analysis accuracy was reflected by average spike recoveries of 76, 79, and 84%, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719908542874

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The formation of inclusion complexes of cyclodextrins (CDs) and Methyl Orange (MO) has been examined by means of paper chromatography. On the basis of a proposed scheme in which there are an equilibrium between free MO and an inclusion complex in the mobile phase, an equilibrium between free MO in the mobile phase and that in the stationary phase of a chromatography paper, and an equilibrium between free inclusion complexes in the mobile and stationary phases, analyses have been made to evaluate these equilibrium constants. In the cases of α- and β-CDs, the equilibrium and the distribution constants for the formation of a 1:1 inclusion complex with MO are in good agreement with reported ones. The distribution of MO into the stationary phase of a chromatography paper is considerably prohibited by the formation of the inclusion complex. The estimated equilibrium constant for the formation of a 1:2 γ-CD-MO inclusion complex is an order of magnitude less than the reported one.

ISSN:0003-2719    

DOI:10.1080/00032719908542875

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The electrochemical determination of chloramphenicol (CAP) in food using mini- and micro- mercury drop electrodes and differential pulse polarography (DPP) has been elaborated. A phosphate buffer with pH 6.6 was used as the basic electrolyte. The analysis was based on a peak at the potential Ep= −0.320 V which showed a clearly linear dependence of the peak current on the concentration of chloramphenicol in the sample under investigation. Prior to the determination of chloramphenicol in actual samples it was necessary to extract this antibiotic with organic solvents such as methanol, ethanol and ethyl acetate.

ISSN:0003-2719    

DOI:10.1080/00032719908542876

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719908542877

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor