oalib

OALib Journal期刊

ISSN: 2333-9721

费用:99美元

投稿

匹配条件: “Zenovia Moldovan” ,找到相关结果约254条。
列表显示的所有文章,均可免费获取
第1页/共254条
每页显示
Spectrophotometric determination of nitrite by its catalytic effect on the oxidation of congo red with bromate
Zenovia Moldovan
Bulletin of the Chemical Society of Ethiopia , 2012,
Abstract: A novel simple, sensitive and rapid kinetic-spectrophotometric method for the determination of trace amounts of nitrite is proposed. The method is based on its catalytic effect on the oxidation of congo red (CR) by potassium bromate in acidic solution. The oxidation reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of CR at a suitable λmax= 570 nm for the first 10–40 s from the start of the reaction. Under the optimum experimental conditions (sulfuric acid, 0.3 M; CR, 0.75x10-4 M; potassium bromate, 5x10-4 M and 25 oC), nitrite can be determined in the range of 0.015–0.75 μg mL 1 with the detection limit of 0.006 μg mL 1. The relative standard deviation of five replicate determination of 0.25 μg mL 1 nitrite was 2.5%. The proposed method was applied satisfactorily to the determination of nitrite in spiked drinking water samples. KEY WORDS: Nitrite, Catalytic effect, Congo red, Spectrophotometry, Drinking water Bull. Chem. Soc. Ethiop. 2012, 26(2), 159-169. DOI: http://dx.doi.org/10.4314/bcse.v26i2.1
Spectrophotometric determination of nitrite by its catalytic effect on the oxidation of congo red with bromate
Zenovia Moldovan
Bulletin of the Chemical Society of Ethiopia , 2012,
Abstract: A novel simple, sensitive and rapid kinetic-spectrophotometric method for the determination of trace amounts of nitrite is proposed. The method is based on its catalytic effect on the oxidation of congo red (CR) by potassium bromate in acidic solution. The oxidation reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of CR at a suitable λmax = 570 nm for the first 10–40 s from the start of the reaction. Under the optimum experimental conditions (sulfuric acid, 0.3 M; CR, 0.75Χ10-4 M; potassium bromate, 5Χ10-4 M and 25 oC), nitrite can be determined in the range of 0.015–0.75 μg mL 1 with the detection limit of 0.006 μg mL 1. The relative standard deviation of five replicate determination of 0.25 μg mL 1 nitrite was 2.5%. The proposed method was applied satisfactorily to the determination of nitrite in spiked drinking water samples.DOI: http://dx.doi.org/10.4314/bcse.v26i2.1
FIRST DERIVATIVE SPECTROMETRY FOR DETERMINATION OF A RUBBER ANTIOXIDANT
Zenovia Moldovan,Lauren?ia Alexandrescu
Analele Universitatii Bucuresti : Chimie , 2004,
Abstract: The aim of our study was to develop a simple method for quantitative estimation of anamine antioxidant, namely 2,2,4 – trimethyl – 1,2 – dihydro – quinoline (TMHQ), used in themanufacture of industrial rubber. In order to avoid the influence of other polymer additives, theanalysis of TMHQ was made by derivative spectrometry. Thus, by applying the first derivativespectrum of TMHQ, Beer’s law has been valid in the concentration range 0.25-10μg TMHQ /mL.Measurements were made at 254 nm. At this wavelength, the first derivative spectra of the otherpolymer additives cross the zero line.
A POLYMER ADDITIVE ESTIMATION BY DERIVATIVE SPECTROPHOTOMETRY
Zenovia Moldovan,Lauren?ia Alexandrescu
Analele Universitatii Bucuresti : Chimie , 2002,
Abstract:
UV Spectrometric Study on a Synergetic System of Polymer Additives
Zenovia Moldovan,Laura Alexandrescu,Valentina Constantinescu
Journal of Applied Sciences , 2007,
Abstract: An UV spectrometric method for the determination of the light stabilizer and the antioxidant from polymeric blends was developed. The investigated antioxidant and light stabilizer were: 2,2`-Methylene bis (6-tertbutyl-4-methylphenole), noted MBP and Tinuvin P (2-(2`-Hydroxy-5`-methylphenyl)-benzothriazole), noted TP. The described procedure works without any separation step of MBP and TP from each other and from the other polymer additives (namely stearic acid and paraffin). The second derivative signal measured at 281 nm was used for the elimination of the interferences of the other additives in the MBP estimation, while for determination of TP, the first derivative was measured at 326 nm. Beer`s law has been valid in the concentration range of 1.5-30 ppm MBP and 1.0-30 ppm TP. The proposed method has been applied to the determination of MBP and TP in synthetic binary and tertiary mixtures and in polymeric blends with certified formula.
SPECTROPHOTOMETRIC METHOD FOR RANITIDINE DETERMINATION IN DRUGS USING RHODAMINE B
ZENOVIA MOLDOVAN,HASSAN Y ABOUL-ENEIN
Journal of the Chilean Chemical Society , 2012,
Abstract: A new spectrophotometric method has been developed for the determination of ranitidine hydrochloride (RHCl) in bulk drug and in tablet formulation. The proposed method involves the addition of a measured excess of bromate-bromide reagent in hydrochloric acid medium to RHCl, followed by determination of residual bromine by reacting with a fixed amount of Rhodamine B (RB) and measuring the absorbance at λmax=557 nm. Beer's law was found in the range of 0.3-3.2 μg ml-1 of RHCl, with a good correlation coefficient (r=0.9997). The limits of detection and quantification were calculated to be 0.08 μg ml-1 and 0.24 μmg ml-1, respectively. The different experimental parameters affecting the development and stability of the proposed method were carefully studied and optimized. The validity of the proposed method tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method, demonstrated good accuracy and precision.
Spectrophotometric determination of trace iron(III) in natural water after its preconcentration with a chelating resin
ZENOVIA MOLDOVAN,ELEONORA-ANA NEAGU
Journal of the Serbian Chemical Society , 2002,
Abstract: A method for the determination of Fe(III) at trace levels is described. Thus, prior to the spectrophotometric determination, a preconcentration of the trace amounts of iron(III) using a chelate forming resin is proposed. A strong base anion-exchange resin (Dowex 2X4) loaded with Ferron (7-iodo-8-hydroxyquinoline-5-sulphonic acid) was used for Fe(III) preconcentration, at pH 2.2. After desorption with 5 % ascorbic acid in 0.5 M HCl, the analyte (converted from Fe(III) to Fe(II) was determined spectrophotometrically at 510 nm as Fe(II)-o-phenanthroline complex. The accuracy of the proposed method was verified by comparing the obtained results with those obtained using AAS with the standard addition method. The sensitivity of the spectrophotometric method (after preconcentration) was 0.01 mg Fe(III)/ml. The recovery for iron(III) at the 7 mg/l level was 97 %.
USE OF DIFFERENT INORGANIC COMPLEXANTS AS ELUENTS FOR CATION-EXCHANGE SEPARATION OF SILVER FROM LEAD
Zenovia Moldovan,Eleonora-Ana Neagu,Rodica Paraschivoiu
Analele Universitatii Bucuresti : Chimie , 2002,
Abstract: In order to separate silver from lead by cation exchange chromatography, different complexants,namely Na2SO3, KSCN, CH3COONH4 were examined as eluents. The best results were obtainedfor 5% Na2SO3. Thus, trace and milligram amounts of silver were separated from lead by elutionof the first with 5% Na2SO3 solution from a column with DOWEX 50 (H+ form). Lead was theneluted with 2M-HNO3. The eluted metal ions were analysed by AAS technique. The separationwas fairly sharp and quantitative and the method was used to analyse synthetic mixtures.
CHARACTERIZATION OF SOME MICROSTRUCTURED POLYMER BLENDS BY MECHANICAL TESTS AND ATR-FTIR SPECTROMETRY
Zenovia Moldovan,Florica Ionescu,Ioana Vasilescu,Simona Litescu
Analele Universitatii Bucuresti : Chimie , 2007,
Abstract: In our study, a series of thermoplastic vulcanizate blends based on ethylene propylene diene terpolymer (EPDM) rubber and high-density polyethylene (HDPE), have been prepared by using different chemical systems of vulcanization. The obtained microstructured polymer blends have been characterized by physical-mechanical tests and by Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometry. The dynamic mechanical analysis correlated with ATR-FTIR spectral characteristics reveals that semi-EV and EV systems containing as cure agents sulfur and two accelerators (Tetramethylthiuram disulfide (TH) and 2 Mercaptobenzothiazole (M)) show improved properties as against conventional cure systems.
EPDM-HDPE Blends with Different Cure Systems/Mechanical and Infra-Red Spectrometric Properties
Zenovia Moldovan,Florica Ionescu,Simona Litescu,Ioana Vasilescu
Journal of Applied Sciences , 2008,
Abstract: The physico-mechanical properties and the Infra-red (IR) spectra (obtained by applying the Attenuated Total Reflectance (ATR) technique) of high density polyethylene (HDPE)/ethylene propylene diene terpolymer (EPDM) blends were investigated using a Zwick Tensile Testing machine and a Fourier Transform Infra-red (FTIR) spectrometer. Three kinds of cure systems were used: sulfur, tetramethylthiuram disulfide (TH) and 2-mercaptobenzothiazole (M); sulfur, tetramethylthiuram disulfide (TH) and zinc-diethyldithiocarbamate (ZDEC); sulfur, tetramethylthiuram disulfide (TH) and diphenylguanidine (D). The composition of HDPE and EPDM was fixed at 50/50 by weight and the ratio cure accelerators/sulfur was varied from 0.4 to 6.34 by weight. Results indicated that polymer alloys EPDM/HDPE containing as cure agents Sulfur, TH and M, in a ratio cure accelerators/sulfur = 6.34 and 1.85, respectively, showed improved physico-mechanical properties as compared to the other polymer blends. This behavior was confirmed by the recorded ATR-FTIR spectra of the studied samples.
第1页/共254条
每页显示


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.