不同Fe(Ⅲ)化合物与ClO-热溶液中化学反应的跟踪观察

采用分光光度法跟踪5种不同的Fe(Ⅲ)化合物分别与高碱度NaClO溶液共热到80 ℃时所发生的变化，发现Fe(Ⅲ)首先被氧化为Fe(Ⅵ)；在聚合硫酸铁、六氟合铁酸钾和氢氧化铁参与的反应体系中，Fe(Ⅵ)在分解生成Fe(OH)₃沉淀的同时，还有Fe(Ⅵ)紫色溶液变成Fe(Ⅳ)绿色溶液的反应存在；在硝酸铁和三氯化铁参与的反应体系中，只有Fe(Ⅵ)分解生成Fe(OH)₃沉淀的反应存在。在反应过程中，聚合硫酸铁、硝酸铁所参与的反应体系中，前者生成Fe(Ⅳ)溶液浓度最高：1.25 × 10^-3 mol·L^-1，后者生成Fe(Ⅵ)溶液浓度最高：0.23 mol·L^-1。     

不对称氧氮氧三齿配体Cu(Ⅱ)配合物催化NA酯水解研究

合成了不对称氮氧杂链型配体N-（2′-羟基)苄基乙醇胺(HL),通过元素分析、IR和 ¹H NMR等手段进行了表征。用pH电位滴定法,在25±0.1℃,I=0.10 (KNO₃)条件下,研究了该配体质子化及其与Cu(Ⅱ)离子配位热力学。在25±0.1℃,I=0.10 (KNO₃), pH=7～9 (50 mol·L^-1缓冲溶液)范围内,通过分光光度法测定了配合物对p-硝基苯酚乙酸酯(NA)水解催化动力学,得到了NA酯催化水解二级反应速率常数k_NP((mol·L^-1)^-1·s^-1)。结果表明：Cu(Ⅱ)离子与醇羟基配位作用较强,并且还与一个水分子有较弱的配位。配位醇羟基和水分子的离解常数pKa分别为7.62和11.22。在中性pH值可以产生具有有很强亲核能力的配位烷氧负离子Cu(Ⅱ)…^-OR,配合物对酯的水解有金属离子Lewis酸活化和亲核试剂进攻双重催化作用,与碱性磷酸酯催化作用比较类似,在pH中性和弱碱性条件下对NA酯水解有很好的催化效果,当pH为9.0时,k_NP达到0.12 (mol·L^-1)^-1·s^-1。     

金表面有机膦酸锆多层膜在不同支持电解质溶液中的稳定性

Zirconium 1,4-butylenediphosphonate[Zr(BDPA)] multilayers on a 3-mercaptopropylphosphonate-coated gold electrode were prepared by the conventional layer-by-layer method. The stability of the Zr(BDPA) multilayers in different supporting electrolyte solutions was studied by cyclic voltammetry(CV) and X-ray photoelectron spectroscopy(XPS) measurements. The results show that the Zr(BDPA) multilayers are very stable in 0.2 mol·L^-1 KCl, 0.2 mol·L^-1 KNO₃ and low concentration phosphate buffer solution(PBS) with low pH values(c≤0.05 mol·L^-1, pH≤6.8). While in high concentration 0.2 mol·L^-1 PBS(pH=5.2～7.4), the Zr(BDPA) multilayers will be partially desorbed within two days, possibly due to the formation of more stable zirconium phosphate.     

Fe(III)与2,3-二羟基苯磺酸钠配位反应的动力学研究

[H⁺]在0.01～0.70 mol•L^－1范围内, 离子强度为1.00 mol•L^－1, [Fe(III)]>>[配体]、[H⁺]>>[配体]的条件下, 研究了Fe(III)与2,3-二羟基苯磺酸钠(Tiron)的配位反应. 发现当[H⁺]≤3.00×10^－2 mol•L^－1时, [Fe(III)]²对反应速率有明显的贡献. 求得了相关反应的动力学参数, 从而揭示了FeOH²⁺和与Tiron配位的解离反应途径及的缔合反应机制, 并提出了该配位反应的可能机理.     

Cu2+和Cu+对原代培养的小鼠成骨细胞增殖、分化和钙化的影响

利用噻唑蓝(MTT)法、碱性磷酸酶(ALP)比活性测定、油红O染色和矿化结节染色及定量分析,研究了Cu²⁺和Cu⁺对原代培养的成骨细胞增殖、分化及钙化的影响。结果显示：Cu²⁺(1×10^-9~1×10^-6 mol·L^-1)促进成骨细胞增殖,随时间延长,促进作用变弱。Cu⁺(1×10^-7~1×10^-5 mol·L^-1)抑制成骨细胞增殖,随时间延长,浓度为1×10^-6 mol·L^-1的Cu⁺为促进作用,其余浓度则没有影响。对于成骨细胞分化,Cu²⁺和Cu⁺表现出相似的影响,浓度为1×10^-9和1×10^-6 mol·L^-1时均促进成骨细胞分化,而当浓度为1×10^-7和1×10^-5 mol·L^-1时,则抑制成骨细胞分化,随作用时间延长,大多数浓度均表现为促进作用。测试浓度下的Cu²⁺和Cu⁺均对成骨细胞向脂肪细胞的横向分化表现为促进效应。对矿化功能的影响,1×10^-5 mol·L^-1的Cu²⁺和Cu⁺表现出显著的抑制效应,但随浓度降低,抑制效应变弱。1×10^-7 mol·L^-1的Cu²⁺ 促进成骨细胞矿化结节的形成。结果提示：作用浓度、作用时间及铜离子的价态都是影响Cu²⁺和Cu⁺生物效应转变(从毒性到活性,从损伤到保护,从下调到上调)的关键因素。     

D301树脂吸附铼(Ⅶ)的研究

本文研究了D301树脂对铼(Ⅶ)的吸附性能,结果表明在T=298 K,pH=2.7的HAc-NaAc缓冲溶液中静态饱和吸附容量为715 mg·g^-1;0.5~5.0 mol·L^-1 HCl溶液可以不同程度地解吸树脂上的铼,其中4.0 mol·L^-1 HCl作为解吸剂时,一次解吸率可达100%。反应开始阶段的表观吸附速率常数k_{298 K}=7.2×10^-5 s^-1;等温吸附服从Freundlich经验式;吸附反应的ΔH=-4.4 kJ·mol^-1;吸附物中树脂功能基与Re(Ⅶ)的物质的量比约为1∶1。并用化学法和红外光谱探讨了吸附机理。     

超声化学法制备树枝状纳米银的研究

Nanostructured silver dendrites were synthesized by using sonochemical method from an aqueous solution of AgNO₃ in the presence of isopropanol as reducing agent and polyethylene glycol (PEG) as disperser. The silver nanostructures were characterized by using TEM， XRD and EDS analysis. The effects of reducing agents， dispersers， concentration of AgNO₃ on the silver dendrites nanostructures were also invetigated. A well-defined nanostructured silver dendrite was prepared by ultrsonic irradiation of the aqueous solution of 0.04 mol·L^-1 silver nitrate， 4.00 mol·L^-1 isopropanol and 0.04 mol·L^-1 PEG400 for 1 h.     

钒(Ⅳ/Ⅴ)电对在碳纸电极上的反应机理研究

采用循环伏安、极化曲线和交流阻抗技术研究了在0.8 mol·L^-1 VOSO₄+3.0 mol·L^-1 H₂SO₄中,V(Ⅳ/Ⅴ)电对在碳纸电极上的反应机理及可能的速度控制步骤。研究结果表明：V(Ⅳ/Ⅴ)电对在碳纸电极上的反应属准可逆过程,且氧化过程包含有后置化学转化步骤,计算得到VO²⁺的扩散系数为4.5×10^-5 cm²·s相似文献   

大环三胺铜(Ⅱ)配合物催化羧酸酯水解动力学研究

合成了大环三胺配体-1,4,7-三氮杂环癸烷([10]aneN₃),并对文献方法进行了改进,简化了步骤,节省了溶剂。在25±0.1 ℃,离子强度I=0.10 mol·L^-1 (KNO₃)条件下,采用pH电位滴定法,测定了配体的质子化常数以及与Cu(Ⅱ)离子的配位平衡常数,讨论了配体与金属离子的配位情况。通过分光光度法,在pH值7～9范围内(2×10^-4 mol·L^-1 tris做为缓冲溶液),研究了配合物催化对-硝基苯酚乙酸酯(NA)水解动力学行为,得到了NA酯的水解速率常数k_cat。结果表明催化水解速率对底物(NA)及配合物浓度均呈一级反应,水解反应遵循速率方程v=(k_catc_Cu²⁺+k_OH^-c_OH^-+…)c_NA;在中性和弱碱性条件下能很好的催化NA的水解,pH=9.19时,催化速率常数达到了4.405×10^-2 mol^-1·L·s^-1,优于国际上同类研究报道的结果;催化反应受酸碱平衡控制。结合滴定结果,提出了催化反应机理。     

二丁基硫醚的合成及其萃取分离钯、铂的研究

用Na₂S·9H₂O和1-溴丁烷合成了二丁基硫醚(简写为M)。以二丁基硫醚为萃取剂进行了钯、铂萃取分离的研究,并采用正交实验,得出了钯、铂分离的最佳条件为c_M=0.344 mol·L^-1,O/A=1∶1,t=6 min,c_H⁺=2 mol·L^-1。测得二丁基硫醚萃取钯的容量大于17 g·L^{-1相似文献}   

Trace determination of malachite green in water samples using dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography-diode array detection

A simple and reliable method has been developed for the rapid analysis of trace levels of malachite green from water samples using dispersive liquid–liquid microextraction and high-performance liquid chromatography-diode array detection. Factors relevant to the microextraction efficiency, such as the type and volume of extraction solvent, nature and volume of the disperser solvent, the effect of salt, sample solution temperature and the extraction time were investigated and optimised. Under the optimal conditions the linear dynamic range of malachite green was from 0.2 to 100.0?µg?L^?1 with a correlation coefficient of 0.9962. The detection limit and limit of quantification were 0.1?µg?L^?1 and 0.3?µg?L^?1, respectively. The relative standard deviation (RSD) was less than 2.6% (n?=?5) and the recoveries of malachite green (5.0?µg?L^?1) from water samples were in the range of 99.2?±?1.7%. Finally the proposed method was successfully applied for the analysis of malachite green from fish farming water samples.     

Voltammetry as the First Method for Direct Determination of a Novel Antagonist of A2A Adenosine Receptors

In this article, for the first time, the analytical method for determination of a novel antagonist of A_2A adenosine receptors (8‐(4‐methoxyphenyl)‐4‐oxo‐4,6,7,8‐tetrahydroimidazo[2,1‐c][1,2,4]triazine‐3‐carbohydrazide, namely IMT), which can be used as a drug for liver diseases, was presented. For this purpose a commercially available boron‐doped diamond electrode (BDDE) in combination with differential pulse voltammetry (DPV) was applied. It was found by cyclic voltammetry (CV) that IMT displays at BDDE, as a sensor, two well‐defined oxidation peaks at potentials of 0.81 and 1.18 V and one reduction peak at 1.1 V vs. Ag/AgCl in 0.1 mol L^?1 acetate buffer (pH 4.5±0.1). The oxidation and reduction mechanism of IMT was proposed. The developed DPV method allowed the successful determination of IMT in the range of 0.05–50 μmol L^?1 with detection limit equal to 0.0094 μmol L^?1 and without any chemical modifications and electrochemical pretreatment of the electrode surface. The proposed procedure allows the determination of IMT in vitro directly from urine samples.     

Kinetics and mechanism of the redox reaction between malachite green and iron(III) in aqueous and micellar media

The kinetics of the oxidation of malachite green (MG⁺) by Fe(III) were investigated spectrophotometrically by monitoring the absorbance change at 618 nm in aqueous and micellar media at a temperature range 20–40 °C; I = 0.10 mol dm^?3 for [H⁺] range (2.50–15.00) × 10^?4 mol dm^?3. The rate of reaction increases with increasing [H⁺]. The reaction was carried out under pseudo-first-order conditions by taking the [Fe(III)] (>10-fold) the [MG⁺]. A mechanism of the reaction between malachite green and Fe(III) is proposed, and the rate equation derived from the mechanism was consistent with the experimental rate law as follows: Rate = (k ₄ + K ₁ k ₅[H⁺]) [MG⁺][Fe(III)]. The effect of surfactants, such as cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecylsulfate (SDS, an anionic surfactant), on the reaction rate has been studied. CTAB has no effect on the rate of reaction while SDS inhibits it. Also, the effect of ligands on the reaction rate has been investigated. It is proposed that electron transfer proceeds through an outer-sphere mechanism. The enthalpy and the entropy of the activation were calculated using the transition state theory equation.     

Voltammetric Determination of 3‐Nitrofluoranthene and 3‐Aminofluoranthene at Boron Doped Diamond Thin‐Film Electrode

The voltammetric behavior of 3‐nitrofluoranthene and 3‐aminofluoranthene was investigated in mixed methanol‐water solutions by differential pulse voltammetry (DPV) at boron doped diamond thin‐film electrode (BDDE). Optimum conditions have been found for determination of 3‐nitrofluoranthene in the concentration range of 2×10^?8–1×10^?6 mol L^?1, and for determination 3‐aminofluorathnene in the concentration range of 2×10^?7–1×10^?5 mol L^?1, respectively. Limits of determination were 3×10^?8 mol L^?1 (3‐nitrofluoranthene) and 2×10^?7 mol L^?1 (3‐aminofluoranthene).     

New extraction procedures for isolation of famotidine from aqueous samples

Liquid-liquid and solid-phase extraction procedures are proposed for famotidine isolation from aqueous samples. The isolation and spectrophotometric determination of famotidine is based on its complexation reaction with thymol blue. The composition of a complex between drug and reagent (1?:?1) was established. Dichloromethane and methanol were used as extraction solvents for LLE and SPE processes. Quantification of famotidine was done spectrophotometrically at 544?nm for dichloromethane or at 434?nm for methanolic extracts. The Beer law is obeyed in the famotidine concentration range 3?·?10^?5?mol?L^?1–2.0?·?10^?4?mol?L^?1 for LLE procedure and 2.0?·?10^?6?mol?L^?1–8.0?·?10^?5?mol?L^?1 for SPE.     

Simultaneous Determination of Thallium and Lead on a Chemically Modified Electrode with Langmuir– Blodgett Film of a p‐tert‐Butylcalix[4]arene Derivative

A new voltammetric sensor, Langmuir–Blodgett (LB) film of a p‐tert‐butylcalix[4]arene derivative modified glassy carbon electrode, was designed and successfully used in simultaneous determination of Tl⁺ and Pb²⁺ by square‐wave anodic stripping voltammetry. Under the optimum experimental conditions, this newly developed sensor reveal good linear response for Tl⁺ and Pb²⁺ in the concentration range of 3×10^?8–4×10^?6 mol L^?1 and 2×10^?7–2×10^?5 mol L^?1 respectively. The detect limits are 2×10^?8 mol L^?1 for Tl⁺ and 8×10^?8 mol L^?1 for Pb²⁺. Using proposed method, Tl⁺ and Pb²⁺ in environment samples were determined with satisfactory results.     

Chemometric Strategies to Develop a Nanocomposite Electrode for Simultaneous Determination of Ascorbic Acid,Dopamine, and Uric Acid

A simple and sensitive method for simultaneously measuring dopamine (DA), ascorbic acid (AA), and uric acid (UA) using a poly(1‐aminoanthracene) and carbon nanotubes nanocomposite electrode is presented. The experimental parameters for composite film synthesis as well as the variables related to simultaneous determination of DA, AA, and UA were optimized at the same time using fractional factorial and Doehlert designs. The use of carbon nanotubes and poly(1‐aminoanthracene) in association with a cathodic pretreatment led to three well‐defined oxidation peaks at potentials around ?0.039, 0.180 and 0.351 V (vs. Ag/AgCl) for AA, DA, and UA, respectively. Using differential pulse voltammetry, calibration curves for AA, DA, and UA were obtained over the range of 0.16–3.12×10^?3 mol L^?1, 3.54–136×10^?6 mol L^?1, and 0.76–2.92×10^?3 mol L^?1, with detection limits of 3.95×10^?5 mol L^?1, 2.90×10^?7 mol L^?1, and 4.22×10^?5 mol L^?1, respectively. The proposed method was successfully applied to determine DA, AA, and UA in biological samples with good results.     

Stripping Voltammetric Determination of Zirconium with Complexing Preconcentration of Zirconium(IV) at a Morin‐Modified Carbon Paste Electrode

A sensitive, selective and economic stripping voltammetry is described for the determination of trace amounts of zirconium at a morin‐modified carbon paste electrode (morin‐MCPE). Zirconium(IV) can be preconcentrated on the surface of the morin‐MCPE due to forming the Zr(IV)–morin complex. The complex produces two second‐order derivative anodic peaks at 0.69 V (vs. SCE) and 0.75 V when linear‐scanning from 0.0 to 1.0 V. The optimum analytical conditions are: 2.2 mol L^?1 HCl, 0.0 V accummulation potential, 90 s accummulation time, 250 mV s^?1 scan rate. A linear relationships between the peak currents at 0.75 V and the Zr(IV) concentration are in the range of 2.0×10^?8 to 3.0×10^?6 mol L^?1. The detection limit is 1.0×10^?8 mol L^?1 (S/N=3) for 120 s accumulation. The RSD for determination of 4.0×10^?7 mol L^?1 Zr(IV) is 4.8% (n=8). The proposed method has been applied to determine zirconium in ore samples, unnecessarily extracted.     

Oxidation of diclofenac sodium by diperiodatoargantate(III) in aqueous alkaline medium and its determination in urine and blood by kinetic methods

The kinetics and oxidation of diclofenac sodium (DFS) by diperiodatoargentate(III) (DPA) in alkaline medium at 298 K and at a constant ionic strength of 0.60 mol dm^?3 were studied spectrophotometrically. The oxidation products were [2‐(2,6‐dicloro‐phynylamino)‐phenyl]‐methenol and Ag(I), identified by LC‐ESI‐MS and IR spectral studies. The reaction between DFS and DPA in alkaline medium exhibits 1:1 stoichiometry. The reaction is first order in [DPA] and has a less than unit order dependence each in [DFS] and [alkali]. Increasing concentrations of IO^?₄ retard the reaction. The active species of DPA proposed to be monoperiodatoargentate(III), and a mechanism is suggested. The rate constants involved in the different steps of the mechanism were determined and are discussed. The activation parameters with respect to a rate‐limiting step of the mechanism were determined. The thermodynamic quantities were also determined. Using the oxidation of DFS by DPA, DFS was analyzed by kinetic methods in urine and blood sample. The proposed method enables DFS analysis in the range from 5.0 × 10^?5 to 5.0 × 10^?3 mol dm^?3. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 336–346, 2010     

Square‐Wave Voltammetric Determination of Paraquat at Carbon Paste Electrode Modified with Hydroxyapatite

The voltammetric behavior of paraquat was investigated at hydroxyapatite‐modified carbon paste electrode HAP‐CPE in K₂SO₄. A method was developed for the detection of the trace of this herbicide, based on their redox reaction. The reduction peaks of paraquat were observed around ?0.70 V and ?1.00 V (vs. SCE) in square‐wave voltammetry. Experimental conditions were optimized by varying the accumulation time, apatite loading and measuring solution pH. Calibration plots were linear under the optimized parameters over the herbicide's concentration range 8–200×10^?7 mol L^?1, with a detection and quantification limits about 1.5×10^?8 mol L^?1 and 6.4 10^?8 mol L^?1, respectively.