摘要:

Spectrophotometric and spectrofluorimetric methods were adopted for the analysis of Famotidine and Ranitidine depending on their reaction with 1,4 Benzoquinone reagent at pH 5.2 and 5.6, respectively. The absorbances of the resulting condensation products were measured at 502 and 508 nm for Famotidine and Ranitidine, respectively. Concentrations adhering to Beer's law were from 40-160 μg.ml−for Famotidine and from 20-100 μg.ml−for Ranitidine.

ISSN:0003-2719    

DOI:10.1080/00032719908542906

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Two simple, rapid, sensitive and accurate methods (A and B) for the microdetermination of melatonin in pure form and in pharmaceutical formulations are developed. Method A is based on the formation of tris(o-phenanthroline)iron(II) complex (ferroin) upon reaction of melatonin with an iron(III)-o-phenanthroline mixture in sodium acetate-acetic acid buffer media. The ferroin complex is colorimetrically measured at λmax510 nm against reagent blank. Method B is based on the reduction of Fe (III) by the drug which forms a colored complex (λmax522 nm) with 2,2-bipyridyl. Optimizations of the experimental conditions are described. Beer's law is obeyed in the concentration range 0.4 – 6.4 μg ml−for A and 0.4 – 7.4 μg ml−for B, respectively. The developed methods are applied successfully for the determination of melatonin in pure form and in melatonin tablets without any interference from common excipients.

ISSN:0003-2719    

DOI:10.1080/00032719908542907

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple and sensitive electrochemical method for the direct determination of labile (monomeric inorganic Al speciation) Al concentration in natural waters is developed in this paper. It is based on the use of a.c. oscillopolarography in the presence of rubeanic acid (RA). The optimal experimental conditions are: 1 mol/L NaAc-HAc buffer (pH 5.4) and a RA concentration of 6x10−4mol/L. The response is linear over the 2x10−7to 2x10−6mol/L concentration range. The detection limit is 1x10−7mol/L and the relative standard deviation (at the 1.2 x 10−6mol/L level) is 5.5%. The method has been applied to the direct determination of labile monomeric Al concentrations in various natural samples. The results were verified by the classic ion exchange method.

ISSN:0003-2719    

DOI:10.1080/00032719908542908

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A laboratory incubation procedure followed by gas chromatographic detection was used to measure phosphine production potential in representative wastewater and sewage sludge sources. Phosphine production potential was determined by measuring the rate of phosphine formation in samples incubated under laboratory conditions over a seven day period when both electron donors and the targeted electron acceptor were not limiting factors. Results of our experiments showed that except the primary effluent and secondary effluent wastewater samples all other samples studied (influent wastewater, various type of sludge and sediment sources) produced phosphine. The minimum phosphine production potential value (0.39 pg/ml wastewater/day) was measured in composite influent wastewater samples while the maximum (268 pg/g wet sludge/day) was measured in sediment samples collected from an open-air sewage treatment plant.

ISSN:0003-2719    

DOI:10.1080/00032719908542909

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Current methods of determining organic acids in ground water are labor-intensive, time-consuming and require a large volume of sample (100 milliliter to 1.0 liter). This paper reports a new method developed to determine aliphatic, alicyclic, and aromatic acids in ground water using liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry (LC/APCI/MS). This method was shown to be fast (less than 1 hour), effective, and reproducible, requiring only 1.0 mL of ground-water sample. Ground water was pH-adjusted, filtered through 0.45 μm filters and directly injected into the LC. A binary solvent system consisting of 40 mM of aqueous ammonium acetate and methanol and a C18 column were used for chromatographical separation. The APCI was operated under negative ionization mode. Selected ion monitoring (SIM) was used for detection and quantitation of the analytes. This method was applied to the analysis of organic acids in ground-water samples collected from an aquifer contaminated with JP-4 fuel hydrocarbons at Wurtsmith Air Force Base in Oscoda, Michigan. Aromatic acids identified in the contaminated ground water includeo-, m-toluic acids (2- and 3-methylbenzoic acids), 2,6-dimethylbenzoic acid, 2,3,5- and 2,4,6-trimethylbenzoic acids and two additional trimethylbenzoic acids with unknown location of methylation. The detection of aromatic acids in groundwater from the KC-135 site provided evidence forin situmicrobial degradation of hydrocarbons occurring in the aquifer.

ISSN:0003-2719    

DOI:10.1080/00032719908542910

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor