还原性负离子的间接荧光检测离子色谱法

采用４个铈柱后反应和３价铈荧光检测的离子色谱法分离维生素Ｃ,亚硝酸根,硫代硫酸根,亚硫酸根,草酸根和碘离子６种还原性负离子,同时也给出了使用这种方法的一些最佳条件。     

新型吸附剂偏磷酸铈对铀酰的吸附性能研究

研究新型吸附剂偏磷酸铈对铀酰离子的吸附行为。分别考察了溶液的pH值、温度、接触时间和铀酰离子初始浓度对偏磷酸铈吸附铀酰离子的影响;通过动力学、热力学以及吸附等温线初步研究了吸附机理;最后探究了共存离子和富里酸对吸附的影响。当溶液的pH值为5、温度为30℃、接触时间为60min、铀酰初始浓度为10~(-3)mol/L时为最佳吸附条件,最大吸附量可达到261.78mg/g;动力学研究表明,偏磷酸铈对铀酰离子吸附行为符合准二级动力学方程;Langmuir吸附等温线模型可以更准确的描述铀酰离子在偏磷酸铈上的吸附过程,说明此吸附过程为单分子层吸附;热力学研究表明,偏磷酸铈对铀酰离子的吸附属于吸热反应,反应自发进行,高温促进吸附行为。     

铈离子与乙酰乙酸乙酯体系引发烯类聚合的研究

<正> 铈离子与醇、醛、酮、α-羟基酸等组成的体系能引发烯类单体进行自由基聚合。关于铈离子与酯类化合物体系文献报道甚少。孙燕慧发现脂肪酸酯或芳香酸酯对铈离子引发丙烯酰胺(AAM)聚合能起促进作用,提高聚合速度只R_(p)但活性较小,相对聚合速度只,为1.3左右。本文研究了二元酸酯、乙酰乙酸乙酯(EACAC)分别与铈离子组成的体系引发AAM聚合,实验结果表明EACAC有很高的活性,它与铈离子组成的体系为一氧化还原引发体系。应用自由基捕捉技术和ESR波谱研究,能检测到由EACAC组分反应产生的自由基,从聚合物端基的FT-IR光谱分析,证实了该自由基能引发单体聚合而成为聚合物的端基。从而讨论了引发机理。     

稀土双氧配合物的电子结构研究

用INDO方法(间略微分重叠法)研究了[Ce(CO_3)_3O_2]_2~(8-)上的电子结构和化学健。研究结果表明,[Ce(CO_3)_3O_2]_2~(8-)的HOMO主要由双氧离子(O_2~(2-))的反键π~*轨道组成,LUMO主要由四价铈的4f轨道组成。双氧离子通过σ配键和π配键与2个铈离子配位,配位后O—O键增强。与三价铈配合物比较,四价铈配合物中4f轨道对成键的贡献增大。     

多金核二氧化铈空心球用于硝基苯酚催化加氢

催化剂的微观结构在催化还原反应、有机物氧化反应及有机物转化反应中起着关键作用。本文利用无模板方法合成了多金核中空二氧化铈微球催化剂。将制备好的二氧化铈中空微球浸渍到一定浓度的氯金酸溶液中,然后多次洗涤除去表面吸附的氯金酸离子,最后通过硼氢化钠还原制成中空氧化铈微球包覆的多金核的核壳结构催化剂。将该核壳结构材料用于硝基苯酚加氢反应与金纳米粒子及氧化铈微球相比,多金核中空二氧化铈核壳结构表现出优越的活性和稳定性。通过这种浸渍洗涤再还原的简单方法合成的多金核二氧化铈催化剂有望应用于生物医药和能源环境等领域。     

一种通过纳米粒子的组装制备基于二氧化铈中孔材料的简易方法

用HF或者HCl作联合剂,三嵌段共聚物表面活性剂作模板剂,通过二氧化铈纳米粒子(或者过渡金属掺杂的二氧化铈纳米粒子)组装形成具有热稳定和晶化孔壁的基于二氧化铈的中孔材料。焙烧该合成的超分子模板中孔结构的材料可以形成具有高比表面的基于二氧化铈的中孔材料,这些中孔材料用不同的光谱技术表征。通过D₂-OH交换测得的二氧化铈表面的羟基在组装过程和中孔材料的稳定性方面至关重要。联结剂中的卤素离子(F和Cl离子)可以替代中孔材料的表面羟基,从而影响这些中孔材料的结构稳定性和光学活性,而用具有3 d的过渡金属在组装前掺杂二氧化铈纳米粒子可以显著地提高中孔材料的光学活性,这种提高主要归结为通过掺杂可以促使能量转移的提高。     

铈离子与4,4′-二乙酰氨基二苯基甲烷体系引发烯类聚合

四价铈离子可与多种有机还原剂组成氧化还原引发体系用于烯类聚合。Samal等报道酰胺化合物如硫代乙酰胺、丁二酰胺、乙酰胺能与铈离子匹配进行丙烯腈(AN)水溶液聚合。我们研究室发现铈离子与乙酰苯胺及其衍生物组成的体系,能顺利引发丙烯酰胺AAM聚合。本工作考察了二酰胺化合物,4,4′-二乙酰氨基二苯基甲烷     

多金核二氧化铈空心球用于硝基苯酚催化加氢（英文）

催化剂的微观结构在催化还原反应、有机物氧化反应及有机物转化反应中起着关键作用.本文利用无模板方法合成了多金核中空二氧化铈微球催化剂.将制备好的二氧化铈中空微球浸渍到一定浓度的氯金酸溶液中,然后多次洗涤除去表面吸附的氯金酸离子,最后通过硼氢化钠还原制成中空氧化铈微球包覆的多金核的核壳结构催化剂.将该核壳结构材料用于硝基苯酚加氢反应与金纳米粒子及氧化铈微球相比,多金核中空二氧化铈核壳结构表现出优越的活性和稳定性.通过这种浸渍洗涤再还原的简单方法合成的多金核二氧化铈催化剂有望应用于生物医药和能源环境等领域.     

铈离子清除超氧物自由基的机理

以光辐照核黄素作为超氧物自由基（Ｏ－２）源，研究了Ｃｅ３＋、Ｃｅ４＋对硝基四氮唑蓝（ＮＢＴ）还原、羟胺氧化的抑制作用和铈离子存在时Ｈ２Ｏ２含量、核黄素光分解、溶解氧消耗的变化以及铈离子价态的变化。从而得知，铈离子可清除Ｏ－２，其机理为：Ｃｅ３＋供给Ｏ－２电子氧化为Ｃｅ４＋，Ｏ－２还原为Ｈ２Ｏ２；Ｃｅ４＋从Ｏ－２获得电子还原为Ｃｅ３＋，Ｏ－２氧化为Ｏ２。所以微量的铈离子可清除大量的Ｏ－２。     

铈离子清除超氧物自由在的机理

以光辐照核黄素作为超氧物自由基（Ｏ２）源，研究了Ｃｅ＾３＋、Ｃｅ＾４＋对硝基四氮唑蓝（ＮＢＴ）还原、羟胺化的抑制作用和铈离子存在时Ｈ２Ｏ２含量、核黄素光分解、溶解氧消耗和变化以及铈离子价态的变化。从而得知，铈离子可清除Ｏ２，其机理为：Ｃｅ＾３＋供给Ｏ２电子氧化为Ｃｅ＾４＋、Ｏ２还原为Ｈ２Ｏ２；Ｃｅ＾４＋从Ｏ２获得电子还原为Ｃｅ＾３＋，Ｏ２氧化为Ｏ２。所以微量的铈离子可清除大量的Ｏ２。     

Uniformly sized molecularly imprinted polymer for d-chlorpheniramine. Evaluation of retention and molecular recognition properties in an aqueous mobile phase

Rapid separation and determination of mixtures of L-ascorbic acid, nitrite, sulfite, oxalate, iodide and thiosulfate by conventional ion chromatography is often difficult due to incomplete separation of L-ascorbic acid and nitrite from the water peak when using eluents giving short elution times for iodide and thiosulfate. Separation of the six species within about 15 min has been achieved by isocratic elution using a resin-based ion-exchange column with a carbonate eluent containing a trace amount of 1,3,5-benzenetricarboxylic acid (BTA) and fluorescence measurement of cerium(III) formed via postcolumn reactions of the separated sample species with cerium(IV). Calibration plots of peak height versus concentration were linear up to 10.0 microM (1.76 ppm) for L-ascorbic acid, 8.0 microM (0.37 ppm) for nitrite, 8.0 microM (0.70 ppm) for oxalate, 80.0 microM (10.2 ppm) for iodide and 25.0 microM (2.80 ppm) for thiosulfate, whilst the sulfite calibration was linear up to 25.0 microM (2.00 ppm) when peak area was plotted against concentration. Detection limits (defined as S/N = 3) were 18 ppb for L-ascorbic acid, 4 ppb for nitrite, 16 ppb for sulfite, 7 ppb for oxalate, 72 ppb for iodide and 37 ppb for thiosulfate. The proposed method was applied successfully to the determination of L-ascorbic acid, nitrite, sulfite, oxalate, iodide or thiosulfate in water samples.     

Oxidation of cerium(III) to cerium(IV) using a mixture of hot concentrated perchloric and sulfuric acids

The oxidation of cerium(III) to cerium(IV) using a hot concentrated mixture of perchloric and sulfuric acids is shown to be quantitative Optimum conditions for the oxidation are described Complete removal of chlorine, an interfering decomposition product of boiling perchloric acid, is achieved by purging the concentrated acid solution with nitrogen before dilution with water The presence of sulfuric acid is essentral, the chief role of sulfuric acid apparently being to stabihze the cerium(IV) as a sulfatocerate complex.     

Indirect determination of uranium by the on-line reduction and fluorimetric detection of cerium(III).

A novel flow injection method has been developed for the indirect determination of uranium by the on-line reduction and subsequent fluorimetric detection of cerium(III). A sample solution containing uranium(VI), prepared as a sulfuric acid solution, was injected into a sulfuric acid carrier solution and passed through a column packed with metal bismuth to reduce uranium(VI) to uranium(IV). The sample solution was merged with a cerium(IV) solution to oxidize uranium(IV) to uranium(VI) and the cerium(III) generated was then monitored fluorimetricaly. The present method is free from interference from zirconium, lanthanides, and thorium, and has been successfully applied to the determination of uranium in monazite coupled with an anion-exchange separation in a sulfuric acid medium to eliminate iron(III). The sample throughput was 25 per hour and the lowest detectable concentration was 0.0042 mg l(-1).     

Ruthenium(III)‐mediated oxidation of D‐mannitol by cerium(IV) in aqueous sulfuric acid medium: A kinetic and mechanistic approach

The oxidation of D ‐mannitol by cerium(IV) has been studied spectrophotometrically in aqueous sulfuric acid medium at 25°C at constant ionic strength of 1.60 mol dm^?3. A microamount of ruthenium(III) (10^?6 mol dm^?3) is sufficient to enhance the slow reaction between D ‐mannitol and cerium(IV). The oxidation products were identified by spot test, IR and GC‐MS spectra. The stoichiometry is 1:4, i.e., [D ‐mannitol]: [Ce(IV)] = 1:4. The reaction is first order in both cerium(IV) and ruthenium(III) concentrations. The order with respect to D ‐mannitol concentration varies from first order to zero order as the D ‐mannitol concentration increases. Increase in the sulfuric acid concentration decreases the reaction rate. The added sulfate and bisulfate decreases the rate of reaction. The active species of oxidant and catalyst are Ce(SO₄)₂ and [Ru(H₂O)₆]³⁺, respectively. A possible mechanism is proposed. The activation parameters are determined with respect to a slow step and reaction constants involved have been determined. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 440–452, 2010     

Spectrophotometric determination of cerium(IV), arsenic(III), and nitrite with promazine hydrochloride

Promazine hydrochloride is proposed as a new reagent for the spectrophotometric determination of cerium(IV), arsenic(III), and nitrite. The reagent forms a red-colored radical with cerium(IV) instantaneously in 0.5?2 M sulfuric acid or 0.5?2.5 M phosphoric acid solution. The red radical exhibits maximum absorbance at 505 nm. An 11-fold molar excess of the reagent is necessary for the full development of the color intensity. Beer's law is valid over the concentration range 0.5–15 ppm in sulfuric acid and 0.5–21 ppm in phosphoric acid. The sensitivities of the reaction in sulfuric and phosphoric acid media are 0.022 and 0.019 μg/cm², respectively. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are reported. The proposed method offers the advantages of good sensitivity, simplicity, rapidity, selectivity, and a wider range of determination without the need for extraction. Arsenic(III) and nitrite are indirectly determined.     

Extraction of trace amounts of cerium(III) by oxides of amines and its separation from cerium(IV)

The solvent extraction of cerium(III) from nitric, hydrochloric and sulphuric acid solutions by 4-(5-nonyl)pyridine oxide and trioctylamine oxide in xylene has been studied. The influence of the concentration of the solvents and salting-out agents is described. From the results of partition experiments attempts have been made to deduce the nature of the extracted species. The investigation shows that cerium(III) can be separated from cerium(IV) from very dilute solutions of mineral acids and also from moderate nitric acid media.     

Determination of submicrogram quantities of ruthenium by catalysis of the cerium(iv)-arsenic(iii) reaction

Ruthenium in amounts of 0 005–0 1 μg (and less if need be) can be determined by its catalysis of the slow reaction between cerium(IV) and arsenic(III) in sulfuric acid solution The rate of the catalyzed reaction is obtained by measuring the concentration of cerium(lV) spectrophotometrically as a function of the time Ruthenium is first separated by carbon tetrachloride extraction of the tetroxide, following argentic oxide oxidation Osmium tetroxide is removed by prior extraction with carbon tetrachloride after differential oxidation with nitric acid Osmium can also be removed by boiling an acid solution with hydrogen peroxide, ruthenium being left in solution     

Sequential injection technique for automated titration: spectrophotometric assay of vitamin C in pharmaceutical products using cerium(IV) in sulfuric acid

For the first time sequential injection analysis (SIA) technique has been employed for titrimetry. A new SI titrimetric spectrophotometric method for the assay of vitamin C in drug formulations was explored. The method is based on the oxidation reaction of vitamin C with cerium(IV) in sulfuric acid media using a spectrophotometer as a detector with the wavelength monitored at 410 nm. A 2(3) factorial design chemometric approach was employed to study the interaction effect of the chemical and system variables, mainly cerium(IV), sulfuric acid concentrations and the flow rate. The results of the chemometric optimization revealed that the optimum operating conditions for the SI titrimetric analysis of vitamin C were 7.0 x 10(-3) M cerium(IV), 0.455 M sulfuric acid and 28.9 microL s-1 flow rate. A linear calibration plot for the determination of vitamin C was obtained in the concentration range between 30 to 200 ppm. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference, thus rendering the method suitable for the determination of the drug in pharmaceutical preparations. The SIA method is found to be accurate when the results were statistically compared with the results obtained by the BP standard method. The SIA method is superior when compared to the conventional titration method, the BP standard method and previous methods with respect to precision and automation in solution handling.     

Spectrophotometric determination of cerium(IV) using a phenothiazine derivative.

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer's law is valid over the concentration range of 1-11 microg/ml with a Sandell's sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).