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101.
JPC – Journal of Planar Chromatography – Modern TLC - A water-in-oil microemulsion has been used for the first time as a mobile phase in thin-layer chromatography of amino acids. A new... 相似文献
102.
Poly(p-chloromethylstyrene-ethyleneglycoldimethacrylate) polymeric microbeads, poly(p-CMS-EGDMA), were synthesized and 1,5,9,13-tetrathiacyclohexadecane-3,11-diol (S4HD) was attached chemically onto the polymeric microbeads. Characterization of all microbeads was done by Fourier transform-infrared spectrometry (FT-IR) and elemental analyzer. The amount of attached 1,5,9,13-tetrathiacyclohexadecane-3,11-diol to the polymer was found to be 2.23 mmol g−1 polymers. The ligand attached microbeads, poly(p-CMS-EGDMA-S4HD), were used to examine the adsorption capacity of Pb(II), Cd(II), Hg(II) and Cr(II) ions for recovery, pre-concentration and the matrix elimination by changing the pH and the initial metal ion concentrations and also adsorption kinetics of the studied metal ions was determined. Pre-concentration factors for the studied toxic metal ions were found to be more than 500-fold and recovery was between 92 and 106%. In the drinking, lake, tap and sea-water samples from water lands, ultra-trace toxic metal ion concentrations were determined easily by using ligand modified microbeads after pre-concentration because of the high pre-concentration factor and easily matrix elimination using ligand modified microbeads. Reference sea-water material was used for the validation of the method and it was found that recovery, pre-concentration and the matrix elimination were performed perfectly. For the desorption of the toxic metal ions, 3 M HCl containing 0.8 M thiourea was used and desorption ratio was obtained more than 96%. 相似文献
103.
The ability of titanium(IV) chloride as a catalyst to promote the Pechmann condensation reaction with a range of phenols and β-keto esters is described.The reaction was carried out by addition of TiCl4 to a mixture of the phenol and the β-keto ester with thorough stirring in the absence of a solvent and represents an improvement on the classical Pechmann conditions. The yields of coumarins obtained via this novel protocol were significantly higher than those using the conventional method and the reaction duration was reduced to a few minutes or even a few seconds. 相似文献
104.
A. A. Fahad A. W. Ali R. M. Shihab 《Journal of Radioanalytical and Nuclear Chemistry》1989,130(1):195-201
Mobility of137Cs was investigated in columns of calcareous loam and clay soils leached under river water, NH4OAc, KCl, CaCl2, and EDTA. Fractionation of Cs into ten sequential fractions was accomplished in the leached soils as well as in soil samples received carrier-free137Cs and incubated for 60 d. At the end of 90 d of leaching with river water and CaCl2, the bulk of Cs applied (>97%) was found to remain in the upper 1 cm of soil columns. On the other hand, the reduction in Cs concentration was approximately 30% with NH4OAc, 18% with KCl, and 10 to 25% with EDTA. The major soil constituents appeared to be responsible for retaining Cs were clay, silt, and Fe oxides. The leaching consistently increased the magnitude of fractions bound to clay minerals and in most cases decreased the fractions of water soluble, exchangeable, carbonate, and organic matter. 相似文献
105.
This determination of salicylate in blood serum is based on application of an immobilized enzyme electrode. Salicylate hydroxylase (E.C.1.14.13.1) is chemically immobilized onto a pig intestine mounted on an oxygen electrode. The signals are monitored amperometrically and the resulting output voltage is read using a simple adapter. The experimental parameters and possible interferences are discussed. Samples containing 1.0 × 10?5?1.87 × 10?3 M (1.6–300 μg ml?1) salicylate were assayed with relative standard deviations between 1.3% and 6% and recoveries between 98.7 and 103%. Results obtained by the proposed method and by the established clinical method for randomly spiked pooled serum samples correlated well (r = 0.99). 相似文献
106.
The spectral properties of o-aminophenol, catechol, o-nitrophenol, pyrogallol, salicylic acid and gallic acid were investigated in different solvents. The behaviour of hydrogen bonding demonstrated in these systems was discussed. 相似文献
107.
Ali Elriati Karin Achilles Jutta Loose Hans-Hartwig Otto 《Monatshefte für Chemie / Chemical Monthly》2007,76(5):627-634
4-Phenylazetidine-2-one was transformed into 4-phenylazetidine-1-alkanoic acids, which were reacted in the presence of diphenylphosphoroazidate
with amino acid esters and dipeptide esters yielding β-lactam peptides with different spacers between the lactam ring and
the peptide moiety. All structures were established by elementary analyses, HPLC, optical rotation, and spectroscopic data
and all new compounds were tested as inhibitors of PPE using standard procedures. Four compounds exhibited a weak activity compared with the standard inhibitor trifluoroacetyl-l-val-l-tyr-l-val. 相似文献
108.
Syed Mashhood Ali Santosh Kumar Upadhyay Arti Maheshwari 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):351-355
Desloratadine (DES) is an antihistamine used in the treatment of allergies and chronic urticaria. 1H NMR spectroscopic study of varying ratios of DES and β-Cyclodextrin (β-CD) in D2O suggests the formation of a 1:1 inclusion complex formed by the penetration of Cl-substituted aromatic ring into the β-CD
cavity. The stoichiometry and binding constant of the complex were determined by Scott’s method. 相似文献
109.
Rahman Hosseinzadeh Ali Sharifi Kourosh Tabar-Heydar Farshid Mohsenzadeh 《Monatshefte für Chemie / Chemical Monthly》2002,133(11):1413-1415
Summary. N,N-Dimethylhydrazones of ketones and aldehydes undergo facile cleavage to the corresponding carbonyl compounds upon exposure
to microwaves in water containing a catalytic amount of PdCl2–SnCl2 in high yields.
Corresponding authors. E-mail: rahman@umz.ac.ir
Received December 27, 2001. Accepted (revised) February 6, 2002 相似文献
110.
Mesoporous high-surface-area alumina was prepared by a modified aerogel procedure. Specific surface areas between 530-685 m(2)g(-1) were obtained after heat treatment at 500 degrees C. Nitrogen adsorption studies have shown that surface areas and pore characteristics change upon decomposition of aluminum hydroxide to oxide as well as upon compaction of oxide powders. The surface area of aluminum hydroxide increased to a maximum, while the pore volume and diameter decreased as the hydroxide was heated to a temperature of 400 degrees C. Heating at higher temperatures resulted in sintering of the particles accompanied by a decline in the surface area. Compaction of activated alumina into pellets was accompanied by a relatively gradual change in the surface area and pore characteristics at pressures below 6.9 x 10(7) Pa, while severe changes took place at a pressure of 1.4 x 10(8) Pa. In situ IR studies of the dehydroxylation of the alumina surface, showed nu(OH) absorptions for isolated surface hydroxy groups centering at 3670, 3714, and 3765 cm(-1), which are shifted to lower frequencies than common literature values. Pyridine was found to adsorb on Al(3+) ions as well as through hydrogen bonding to relatively acidic surface OH groups, and IR spectra indicated the presence of strong Lewis acid sites. 相似文献