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A sensitive catalytic kinetic spectrofluorimetric method for determining ng ml(-1) of selenium by flow injection analysis has been developed. The method, based on the catalytic effect of Se (IV) on the reduction of resorufin by sulphide, in the presence of cetylpyridinium chloride, is monitored spectrofluorimetrically (lambda(ex)=480 nm; lambda(em)=583 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. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 1 ng ml(-1) Se (IV), and the calibration range is 5-1000 ng ml(-1). Sampling rate is 60 samples h(-1), and the relative standard deviation of 12 determinations of 100 ng ml(-1) Se was 0.76%. The determination of Se (IV) in the presence of Se (VI) and total selenium is described. The method was applied to the determination of Se in selenium tablets, and several synthetic samples. 相似文献
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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
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Various aluminum alkoxide precursors have been used for the preparation of boehmite by hydrothermal assisted sol-gel processing. The coordination status of aluminum in solution for all precursors employed for the preparation of boehmite phase was determined by 27Al NMR and correlation between coordination status of aluminum atoms of precursors and development of boehmite phase has been investigated. Hydrothermal assisted hydrolysis of aluminum alkoxides where the aluminum atoms are four or five coordinated in solution resulted in the formation of boehmite. In contrast, hydrothermal hydrolysis of aluminum alkoxides where the aluminum atoms are six coordinated resulted in the formation of amorphous gel. Development of boehmite phase by hydrothermal hydrolysis of aluminum alkoxides at various temperatures was pursued by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. 相似文献
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A sensitive kinetic spectrophotometric method for the determination of ng amounts of sulfide has been developed based on the reduction of Azure A by sulfide in the presence of Brij-35 at pH 7. The decrease in absorbance of Azure A at 600 nm is proportional to the concentration of sulfide over the range 25-1,400 ng mL(-1). The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 17 ng mL(-1), and the relative standard deviation of seven determinations of 500 ng mL(-1) sulfide was 2.1%. The method was applied to the determination of sulfide in spring water. 相似文献
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Electron-rich aromatic compounds react with formaldehyde and a secondary amine under solvent-free condition, in the presence of acidic alumina in a commercial microwave oven or at room temperature to produce aminomethylated products in good to excellent yields. 相似文献
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Mirzaee Razieh Soltanabadi Azim Ranjbar Sharam Fakhri Zahra 《Structural chemistry》2021,32(6):2319-2332
Structural Chemistry - Thermodynamic properties of binary mixtures of 2-methylcyclohexanol with morpholine are measured as a function of composition and temperature. The excess molar volumes were... 相似文献
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Ali Reza Mahdavian Mahdi Abdollahi Leila Mokhtabad Farshid Ziaee 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1583-1596
Many reports exist in the literature about the application of 1H and 13C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line 1H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well. 相似文献
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Mohammad Ghaffarzadeh Mohammad Bolourtchian Zohreh Hassanzadeh Fard Mohammad Reza Halvagar Farshid Mohsenzadeh 《合成通讯》2013,43(14):1973-1981
One‐step microwave‐assisted synthesis of phenylacetylenes 2a–j from the corresponding ketones 1a–j in the presence of a new reagent, PCl5–pyridine, is described. The reaction is carried out under a simple operational and experimental procedure, avoiding the use of the complicated and harsh multistep reaction. 相似文献
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Four‐component reaction of aminodiazines (2‐aminopyrimidine and 2‐aminopyrazine), glyoxal, formaldehyde, and methanol yields trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrimidinyl)imidazolidine (5a) and trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrazinyl)imidazolidine (5b), respectively. Changing methanol to acetonitrile leads to the formation of the corresponding 1,3‐bis(2‐pyrimidinyl) and‐1,3‐bis(2‐pyrazinyl)‐ derivatives of trans‐4,5‐dihydroxyimidazolidine (6). Details of the proposed mechanism are discussed. 相似文献