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1.
Polarographic determination of uranium (VI) has been studied in the organic extraction phase TBP—diluent along with a selected
aprotic solvent (i. e. dimethyl sulfoxide or N,N-dimethylformamide). DMF was found more suitable because it dissolves the
organic extraction phase better than DMSO. U (VI) extracted in TBP-kerosene, n-hexane, cyclohexane, n-dodecane, benzene, from
nitric acid medium can be determined in an organic solution (e. g. 50% DMF-30% TBP-20% kerosene) where it gives a well defined
wave. In the organic solution, nitric acid added and/or extracted from the aqueous phase was found as an excellent supporting
electrolyte for uranium determination. 相似文献
2.
Summary The influence of the isothermal temperature, program rate, initial temperature and flow rate on retention indices was studied. The methods of Kováts, Van Den Dool and Local Lagrange Interpolation are compared. Ten experimental measurements were carried out on a capillary column coated with OV-101 stationary phase. 相似文献
3.
Fayçal Boukhari Nacéra Tigrine‐Kordjani Brahim Youcef Meklati 《Helvetica chimica acta》2013,96(6):1168-1175
Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non‐insulin‐dependent diabetics. In recent years, the type‐II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwave‐assisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC‐FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050±0.001% (w/w)) than by HD (0.030±0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with β‐caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with β‐pinene and eucalyptol, respectively, as major components. 相似文献
4.
Linda Didaoui A. Touabet A. Y. Badjah Hadj Ahmed B. Y. Meklati Werner Engewald 《Journal of separation science》1999,22(10):559-564
In reversed phase liquid chromatography (RP-HPLC), the validity of a multiparametric non-linear least-squares regression iterative method for the determination of the column dead time tM and the regression parameter (slope b), based on the use of alkan-2-ones, alkyl aryl ketones, and 1-nitroalkanes has been evaluated. The determination of tM and b has been extensively studied for two mobile phase systems acetonitrile-water and methanol-water on seven octadecyl-C18 and one octyl C8 analytical columns. The calculated tM and b values were compared with those obtained by Guardino's and Grobler's methods. The influence exerted thereon by the nature of the homologous series, the mobile phase composition, and the packing materials were investigated. 相似文献
5.
6.
An improved microwave Clevenger apparatus for distillation of essential oils from orange peel 总被引:5,自引:0,他引:5
Microwave Clevenger or microwave accelerated distillation (MAD) is a combination of microwave heating and distillation, performed at atmospheric pressure without added any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. MAD extraction of orange essential oil was studied using fresh orange peel from Valencia late cultivar oranges as the raw material. MAD has been compared with a conventional technique, which used a Clevenger apparatus with hydro-distillation (HD). MAD and HD were compared in term of extraction time, yields, chemical composition and quality of the essential oil, efficiency and costs of the process. Extraction of essential oils from orange peels with MAD was better in terms of energy saving, extraction time (30 min versus 3 h), oxygenated fraction (11.7% versus 7.9%), product yield (0.42% versus 0.39%) and product quality. Orange peels treated by MAD and HD were observed by scanning electronic microscopy (SEM). Micrographs provide evidence of more rapid opening of essential oil glands treated by MAD, in contrast to conventional hydro-distillation. 相似文献
7.
K. Si Ahmed F. Tazerouti A. Y. Badjah-Hadj-Ahmed B. Y. Meklati 《Chromatographia》2005,62(11-12):571-579
Two chiral stationary phases for high-performance liquid chromatography (HPLC) have been synthesized by grafting native and 2-hydroxypropyl-β-cyclodextrin onto silica gel by a previously described method. They were tested under reversed-phase conditions. These two materials enable separation of the enantiomers of a variety of drugs (benzodiazepine anxiolytics, arylpropionic acids, anti-inflammatory and anticoagulant agents) and herbicides (aryloxyphenoxypropionic esters). Both chiral stationary phases enabled good chiral recognition in reversed-phase mode. The effects of the nature and composition of the mobile phase, of compound structure (mechanisms of chiral discrimination), and of flow-rate were studied. 相似文献
8.
Hania Hebbache Zakia Hank Sultana Boutamine M'hamed Meklati Christian Bruneau Jean-Luc Renaud 《Comptes Rendus Chimie》2008,11(6-7):612-619
The direct condensation of amines with β-ketoesters to produce functional enamine derivatives has been investigated with iron Lewis acid catalysts. FeCl3·6H2O shows good catalytic activity and makes possible the chemo- and stereoselective formations of (Z)-enamine derivatives from aliphatic and aromatic primary amines under mild conditions. 相似文献
9.
Si Ahmed K Tazerouti F Badjah-Hadj-Ahmed AY Meklati BY 《Journal of separation science》2007,30(13):2025-2036
A phenylcarbamate derivative of 2-hydroxypropyl-beta-CD bonded stationary phase was prepared by a previously described method. Its enantiomeric recognition abilities were evaluated as chiral stationary phase (CSP) in normal, polar organic and RP conditions by HPLC. The relevant structural features of the prepared stationary phase which make it an effective chiral selector are discussed. This material seems to have an excellent enantioselectivity for a variety of racemic analytes in the three modes. Hence it can be considered a highly effective multimodal column. Retention factor (k), selectivity (alpha) and resolution (R(s)) were the chosen parameters to describe the column performance. Optimization of these separations was discussed in terms of mobile phase composition, flow rate and structural patterns of the injected analytes. 相似文献
10.
Mokhtar Benalia Ahmed Yacine Badjah-Hadj-Ahmed Mebrouk Djedid B. Youcef Meklati A. H. Al-Dujaili Fouad Ferkous 《Chromatographia》2007,66(7-8):565-570
The investigation of the analytical properties of two new nematic sulphur-containing liquid crystals 5-(4-methoxyphenyl)-azophenyl)-2-butylthio-1,3,4-oxadiazole
(Phase I) and 5-(4-(propoxyphenyl)-azophenyl)-2-butyl thio-1,3,4-oxadiazole (Phase II) and which comprise units of 1,3,4-oxadiazole
instead of the aromatic cycles, was carried out by gas chromatography using glass capillary columns. For this purpose, many
solutes belonging to various families and having different polarities and volatilities were injected. Comparison of the retention
data of the studied components has shown that Phase II allowed a better separation than the other phase. The two liquid crystalline
materials show a good separation of the studied isomers except for xylene. 相似文献