Rate constant for the reaction of the t-butoxyl radical with Fe(II) ion

The rate of the reaction of the tert-butoxyl radical (t-BuO^√) with Fe²⁺ was measured using laser flash photolysis of methanolic solutions at room temperature. t-BuO^√ were generated by homolytic photodecomposition of di-tert-butyl peroxide. The rate constant for oxidation of Fe²⁺ with t-BuO^√ radicals was studied under pseudo-first order conditions. On the basis of competitive kinetics the quantum yield of oxidation, Φ(Fe³⁺), was determined as function of Fe²⁺ concentration by measuring the absorbance of Fe³⁺ as [FeCl]²⁺ complex. By using the literature values of the rate constants of relevant competing reactions, the desired rate constant was determined to be 3.0×10⁸ M⁻¹ s⁻¹.     

A Novel Coumarin-based Fluorescence Chemosensor for Fe^3＋

A novel coumarin derivative[7-diethylamino-2-oxo-2H-chromene-3-carboxylic acid（6-amino-pyridin2-yl）-amide,CFe1] has been synthesized and its potential application as a chemosensor for the detection of metal ions has been further investigated.The responses of CFe1 to Fe^3＋ were studied by fluorescence emission spectrometry in the presence of other metal ions such as Al^3＋,Ba^2＋,Ca^2＋,Co^3＋,Cr^3＋,Cu^2＋,Fe^2＋,Hg^2＋,Mg^2＋,Mn^2＋,Na^＋,Ni^＋,Pb^2＋,Zn^2＋,K^＋,and Ag^＋.CFe1 showed a good selectivity for Fe^3＋ with fast response,a wide pH span of 3.3-9.18,and a large Stocks shift.CFe1 in the presence of Fe^3＋ and ethylene diamine tetraacetic acid（EDTA） makes the blue solution fade to colorless,which is due to the formation of CFe1-Fe^3＋ complex instead of any catalytic action of Fe^3＋.Furthermore,the imaging of Fe^3＋ in cultured single mice microglia cells was realized with the aid of CFe1,indicating that CFe1 has a great potential to be used as promising models for the future design of novel and robust chemosensor for metal ion detection in the field of biomedical and environmental analyses.     

高效液相色谱法同时测定水体中氧氟沙星及其手性异构体

建立了一种简单快捷的手性配位交换高效液相色谱测定地表水中氧氟沙星及其手性异构体的方法,并研究了常见金属阳离子（Ca²⁺、Mg²⁺、Fe³⁺、Zn²⁺）和腐殖酸（HA）对二者分离的影响。采用C₁₈色谱柱（25 cm×0.46 cm,5 μm）,流动相为pH值4.5的20%（v/v）甲醇水溶液（含4 mmol/L异亮氨酸（配体）和3 mmol/L CuSO₄）,流速为1.0 mL/min,柱温为40℃,检测波长为293 nm。氧氟沙星及其手性异构体左氧氟沙星可在18 min内分离,分离度（R）为2.70。结果表明,不同金属阳离子和腐殖酸对手性分离未见明显影响,但会降低氧氟沙星及其手性异构体的峰面积,其中Fe³⁺和高浓度腐殖酸的影响最大。该法能够快速高效测定地表水中氧氟沙星及其手性异构体,但在测试中需考虑Fe³⁺和高浓度腐殖酸的影响。     

Novel Fluorescent Chemosensors Based on Tryptophan Unit for Cu2+ and Fe3+ in Aqueous Solution

We reported four fluorescent chemosensors containing tryptophan units. The fluorescence spectrum titration experiments suggest that chemosensors 1, 2, 3 and 4 are highly selective for Cu²⁺ and Fe³⁺ over Li⁺, Na⁺, K⁺, Co²⁺, Zn²⁺, Ni²⁺, Hg²⁺ and Cr³⁺ via forming complexes with Cu²⁺ or Fe³⁺, which is confirmed by dramatical quench of fluoreseence in aqueous solution at pH 7.4, thus making all the chemosensors suitable for Cu²⁺ and Fe³⁺ fluorescent sensors.     

Multi-functional Photoelectric Sensor Based on a Three-fold Interpenetrated Cd(II) Coordination Polymer for Sensitively Detecting Different Ions

Athree-fold interpenetrated cadmium coordination polymer[Cd₃(BTC)₂(H₂O)₉]·2H₂O(CP 1)(H₃BTC=1,3,5-benzenetricar-boxylic acid) was selected and synthesized to investigate its photoelectric properties. CP 1 showed excellent sensitivity for Cr₂O₇^2- and Fe³⁺, low limit of detection(LOD:0.39 µmol/L for Cr₂O₇^2- and 1.72 µmol/L for Fe³⁺) and stability as electrochemical sensor. More importantly, fluorescence sensing studies indicated that CP 1 exhibits sensing activity for Fe³⁺, Fe²⁺, and MnO₄^- with good cyclic stability and selectivity. Low LOD and high-sensitivity capability of CP 1 make it a potential multifunctional photoelectric sensor.     

PMBP与中性磷萃取剂对铽(Ⅲ)的协同萃取

本文研究了1-苯基-3-甲基-4-苯甲酰基吡唑啉酮-5(PMBP)与丁基膦酸二丁酯(DBBP)或磷酸三丁酯(TBP)的氯苯溶液在硝酸介质中对铽(Ⅲ)的协同萃取。测得了萃合物的组成及其萃取平衡常数,讨论了萃合物的可能结构式及协同萃取机理。     

Metal-organic framework as a multi-component sensor for detection of Fe3+, ascorbic acid and acid phosphatase

In this research,a hydroxyl group functionalized metal-organic framework(MOF),UiO-66-(OH)₂,was synthesized as a "on-off-on" fluore scent switching nanoprobe for highly sensitive and selective detection of Fe³⁺,ascorbic acid(AA) and acid phosphatase(ACP).UiO-66-(OH)₂ emits yellow-green light under ultraviolet light,when Fe³⁺ was added,Fe³⁺ was chelated with hydroxyl group,the electrons in the excited state S_1 of the MOF transferred to the half-filled 3 d orbits of Fe³⁺,resulting in fluorescence quenching because of the nonradiative electron/hole recombination annihilation.AA could reduce Fe³⁺ to Fe²⁺,which can destroy the electron transfer between UiO-66-(OH)₂ and Fe³⁺ after AA adding,resulted in nonoccurrence of the nonradiative electron transfer,leading to the recovery of UiO-66-(OH)₂ fluorescence intensity.The probe can also be used to detect ACP based on the enzymolysis of 2-phospho-L-ascorbic acid(AAP) to produce AA.Benefitting from the hydroxyl group and the characteristics of UiO-66,including the high porosity and large surface area,the developed UiO-66-(OH)₂ showed extensive advantages as a fluorescent probe for detection of multi-component,such as high sensitivity and selectivity,colorimetric detection,fast response kinetics and easy to operate,economical and secure.This is the first time to use active group functionalized MOFs as a multicomponent sensor for these three substances detection.     

Separation Cd(Ⅱ), Fe(Ⅲ) and Zn(Ⅱ) from Eu(Ⅲ) in Sulfuric Acid with Cyanex302 by Using Microporous Hollow Fiber Membrane

With the development of chemical industry, refining and collecting valued material in dilute solutions or difficult separation systems has become one of important research aspects. In order to adapt to the demand of modem science and technology, separation Zn²⁺, Cd²⁺ and Fe³⁺ from Eu³⁺ solution to making Eu with high purity is necessary. Hollow fiber membrane (HFM) extraction, as a new separation technique, has many advantages^[1]. The extractant(commercial name as Cyanex302), bis(2,4,4-trimethylpentyl)monothiophosphinic acid, is a soft acid and so it is easy to extract transition elements^[2]. HFM extraction combined with a new extraction system, which had little consumption and no pollution and was a friend environment process.     

Determination of iron(III) with salicylic acid by the fluorescence quenching method

The spectrofluorimetric determination of Fe³⁺ using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe³⁺–salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe³⁺, occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of the ferric ion is in the range 1×10⁻⁶–10×10⁻⁶ M Fe³⁺ (0.0558–0.558 μg/ml) and the detection limit is 5×10⁻⁸ M. The quenching effect of Fe³⁺ on the fluorescence intensity of salicylic acid may be considered on the basis of complexation between salicylic acid and Fe³⁺. The effects of foreign ions were investigated.     

Gas phase studies of the interactions of Fe2+ with cysteine-containing peptides

Gas-phase complexes of cysteine-containing peptides and Fe²⁺ were produced by fast atom bombardment and studied by tandem mass spectrometry. Specific and strong interactions of the iron and sulfur from the thiol group of the cysteine side chain are preserved in the gas phase and are the basis for highly specific fragmentation to give abundant [a_n − 2H + Fe]⁺ ions, where n is position of the cysteine residue from the N-terminus of peptide. Metal/peptide complexes containing more than one Cys residue were also investigated; they display similar chemistry upon collisionally activated decompositions, indicating that the Fe²⁺ ion primarily binds at cysteine sites.     

含磷酰杂菲侧基的苯乙烯衍生物聚集诱导发光特性及其在过渡金属离子检测中的应用

以2-(6-氧化-6-氢-二苯基(c,e)<1,2>氧杂磷酰基)-1,4-二羟基苯(ODOPB) 为中心结构单元, 通过两步酯化反应, 在两侧分别引入4-戊氧基苯甲酰基和4-乙烯基苯甲酰基, 得到苯乙烯衍生物(MED).由于磷酰杂菲基团的大π共轭结构和极性共同作用, 使得形成聚集体后分子内转动受到限制, 降低了非辐射去活效率, 使 MED在达到一定聚集程度时, 荧光强度成倍增加, 呈现出聚集诱导发光增强(AIEE) 特性. 同时, Pt²⁺, Ru³⁺, Fe³⁺的加入对MED有显著的猝灭效果; 而Fe²⁺只是在形成聚集体过程中才有猝灭效果.     

A New Tetrasubstituted Imidazole Based Difunctional Probe for UV-spectrophotometric and Fluorometric Detecting of Fe3+ Ion in Aqueous Solution

Two new compounds,4-(2-bromophenxl-4,5-diphenyl-imidazol-1-yl)ani 1 ine(probe 1)and 4-[2,4,5-tris(4-bromopheny1)-1H-imidazol-1-y1]aniline(probe 2),were synthesized via a soft and high-efficiency one-pot microwave-assisted method under solvent-free conditions.Their sensing to different metal ions was detected by UV spectrophotometry and fluorescence spectrometry.Probe 2 revealed highly selective and sensitive UV and fluorescence response to Fe^3+ion.Upon the addition of Fe^3+ion,probe 2 showed obvious color change of the solution,conspicuous absorbance enhancement and relatively quick fluorescence quenching.The detection limit for Fe^3+ion was respectively calculated to be 0.72μmol/L(fluorescent detection)and 0.48μmol/L(UV-spectnim detection).Also,probe 2 was bound by Fe^3+ion to tonn a 1:1 complex.Moreover,preliminary application of probe 2 tor detecting Fe^3+ion in aqueous solution was attempted,and satisfying results were obtained.     

Determination of labile Cu(2+) in fresh waters by chemiluminescence: interference by iron and other cations

Analysis of labile Cu²⁺ in fresh waters using the Cu²⁺-catalysed oxidation of 1,10-phenanthroline by superoxide anion radical has been investigated. It was found that certain metal ions, notably Fe³⁺, Fe²⁺ and Pb²⁺ enhance the chemiluminescence (CL) intensity of this reaction by up to an order of magnitude when present in the μM concentration range. This enhancement is considered to arise through coordination of the metal ion to 1,10-phenanthroline, which prevents free rotation of the benzene rings in the excited state intermediate thought to be responsible for light emission. This introduces a potential interference when analyzing fresh waters, which usually contain Fe³⁺ concentrations of this magnitude. However, the enhancement effect saturates at about 4 μM Fe³⁺, so that reliable results can be obtained if the water sample is supplemented with Fe³⁺ to reach this level. Application of the enhanced technique to a river water, and a reservoir to which CuSO₄ had been added to control algal growth, are described. In both cases, only a small fraction of total dissolved Cu²⁺ is labile with respect to the chemiluminesence method.     

Reactivity of tri- and tetra-nuclear ethylidyne cyclopentadienylcobalt clusters towards protonic acids

The bis(μ₃-ethylidyne) tricobalt cluster [(CpCo)₃(μ₃-CCH₃)₂] (1b) is protonated by trifluoroacetic acid to give the dicobalt edge-protonated cation [H(CpCo)₃(μ₃-CCH₃)₂]⁺ [lb + H]⁺. Protonation of the μ₃-ethylidyne tetracobalt cluster hydride [H(CpCo)₄(μ₃-CCH₃)] (3) takes place in two consecutive steps. At low temperature [H₂(CpCo)₄(μ₃-CCH₃)]⁺ [3 + H]⁺ is formed first, and is then slowly converted into [H₃(CpCo)₄(μ₃-CCH₃)]²⁺ [3 + 2H]²⁺ by an excess of acid. As judged by the ¹H NMR data and the crystal structure of [3 + X]⁺[(CF₃COO)₂X]⁻ (X = H or D) the endo hydrogens in [3 + H]⁺ and [3 + 2H]²⁺ occupy μ₃-(Co₃) face capping hydridic positions. The cations [1b + H]⁺ and [3 + H]⁺ show hydride fluxionality in solution, which in the case of [3 + H]⁺ can be frozen out on the NMR timescale at low temperature (ΔG ^≠ (203 K) = 40.8 kJ/mol). The structure of [3 + X]⁺ [(CF₃COO)₂X]⁻ (X = H or D) was determined by X-ray crystallography. One of the hydrides/deuterides is located on the crystallographic mirror plane, capping a tricobalt face of the cluster cation. The other endo hydrogen atom is believed to be disordered between the other two μ₃-(Co₃) sites, which are related by space group symmetry. Deuteronation of 3 shows a strong normal kinetic deuterium isotope effect. From the temperature independence of the ¹H NMR spectrum of [3 + 2D]²⁺ a non-fluxional solution structure can be inferred. In all the systems studied, hydridic (μ₂- or μ₃-) sites are thermodynamically preferred to possible isomeric agostic CoHC or Co₂HC sites for the endo hydrogens. Agostic interactions cannot, however, be ruled out in transient intermediates during the course of the protonations.     

QUANTITATIVE ANALYSIS OF VERY WEAK ACID AND BASE BY pH-FIXED TITRATION METHOD

pH-fixed titration method for the determination of weak acids and bases has been studied in this paper.It is not necessary to know the ionization constant of weak acid or base and the concentration of titrant.This method had been applied to determine phenol, 4-aminoantipyrine and glycine, whose ionization constants range from 10^-10 to 10^-12.The results were satisfactory.     

荧光素-层状双金属氢氧化物复合体的发光性能及对Fe3+的荧光识别

采用离子交换法合成了FLN/OS-LDH复合体(FLN: 荧光素, OS: 1-辛烷磺酸钠, LDH: 镁铝型层状双金属氢氧化物), 并研究了其光致发光和对Fe³⁺的识别性能. 固态时, FLN不发光, 而FLN/OS-LDH复合体呈黄绿色荧光(发射波长为565 nm), 是荧光素(FLN)的特征发射光. 在甲酰胺(FM)中可将该复合体方便剥离为胶状悬浮液, 其发射波长发生蓝移, 为绿光发射(531 nm). 研究了复合体剥离液对金属离子的荧光识别特性, 发现其对Fe³⁺的选择性识别能力很强, 远优于其它离子(Mg²⁺, Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺和Hg²⁺). 该复合体与Fe³⁺结合发生荧光猝灭现象, 可将其用作检测Fe³⁺的荧光传感器. Fe³⁺检测限为1.27×10^-7 mol/L, 猝灭常数(K_sv)为3.44×10² L/mol.     

11-Mercaptoundecanoic acid functionalized gold nanoclusters as fluorescent probes for the sensitive detection of Cu2+ and Fe3+ ions

Metal ions are physiologically essential,but excessive metal ions may cause severe risk to plants and animals.Here,we prepared gold nanoclusters(Au NCs) protected by 11-mercaptoundecanoic acid(11-MUA),which have excellent fluorescence properties for the detection of metal ions.The results showed that the copper ions(Cu~(2+)) and iron ions(Fe~(3+)) in the solution have obvious quenching effect on the fluorescence intensity of Au NCs.The detection range of Fe~(3+) was 0.8–4.5 mmol/L(R~2= 0.992) and 4.5–11.0 mmol/L(R~2= 0.997).And Cu~(2+) has a lower linear range(0.1–1.0 mmol/L,R2= 0.993).When EDTA was added into the reaction system,it was observed that the quenching effect of Cu~(2+) and Fe~(3+)on Au NCs showed different phenomenon.Then,the effect of metal ions on the fluorescence of Au NCs was investigated.The selective detection of Cu~(2+) was achieved by EDTA masking of Fe~(3+).In addition,we realized the metal ions detection application of Au NCs in the serum     

Novel approaches to analysis by flow injection gradient titration

Two novel procedures for flow injection gradient titration with the use of a single stock standard solution are proposed. In the multi-point single-line (MP-SL) method the calibration graph is constructed on the basis of a set of standard solutions, which are generated in a standard reservoir and subsequently injected into the titrant. According to the single-point multi-line (SP-ML) procedure the standard solution and a sample are injected into the titrant stream from four loops of different capacities, hence four calibration graphs are able to be constructed and the analytical result is calculated on the basis of a generalized slope of these graphs. Both approaches have been tested on the example of spectrophotometric acid–base titration of hydrochloric and acetic acids with using bromothymol blue and phenolphthalein as indicators, respectively, and sodium hydroxide as a titrant. Under optimized experimental conditions the analytical results of precision less than 1.8 and 2.5% (RSD) and of accuracy less than 3.0 and 5.4% (relative error (RE)) were obtained for MP-SL and SP-ML procedures, respectively, in ranges of 0.0031–0.0631 mol L⁻¹ for samples of hydrochloric acid and of 0.1680–1.7600 mol L⁻¹ for samples of acetic acid. The feasibility of both methods was illustrated by applying them to the total acidity determination in vinegar samples with precision lower than 0.5 and 2.9% (RSD) for MP-SL and SP-ML procedures, respectively.     

New aspects of the reaction of silver(I) cations with the ethylenediaminetetraacetate ion

The highly neutralized ethylenediaminetetraacetate (EDTA) titrant (95–99% as Y⁴⁻ anion) precipitates with Ag⁺ cations to form the Ag₄Y species, in aqueous medium, which is well characterized from conductometric titration, thermal analysis and potentiometric titration of the silver content of the solid. The precipitate dissolves in excess Y⁴⁻ to form a complex, AgY³⁻. Equilibrium studies at 25°C and ionic strength 0.50 M (NaNO₃) have shown from solubility and potentiometric measurements that the formation constant (95% confidence level) β₁ = (1.93 ± 0.07) × 10⁵ M⁻¹ and the solubility products are K_S0 = [Ag +]⁴[Y⁴⁻] = (9.0 ± 0.4) × 10⁻¹⁸ M⁵ and K_S1 = [Ag +]³[AgY³⁻] = (1.74 ± 0.08) × 10⁻¹² M⁴. The presence of Na⁺, rather than ionic strength, markedly affects the equilibrium; the data at ionic strength 0.10 M are: β₁ = (1.19 ± 0.03) × 10⁶ M⁻¹, K_S0 = (1.6 ± 0.4) × 10⁻¹⁹ M⁵ and K_S1 = (1.9 ± 0.5) × 10⁻¹³ M⁴; at ionic strength tending to zero; β₁ = (1.82 ± 0.05) × 10⁷ M⁻¹, K_S0 = (2.6 ± 0.8) × 10⁻²² M⁵ and K_S1 = (5 ± 1) × 10⁻¹⁵ M⁴. The intrinsic solubility is 2.03 mM silver (I) in 0.50 M NaNO₃. Well-defined potentiometric titration curves can be taken in the range 1–2 mM with the Ag indicator electrode. Thermal analysis revealed from differential scanning calorimetry a sharp exothermic peak at 142°C; thermal gravimetry/differential thermal gravimetry has shown mass loss due to silver formation and a brown residue, a water-soluble polymeric acid (decomposition range 135–157°C), tending to pure silver at 600°C, consistent with the original Ag₄Y salt.     

Fe~(3+)辅助煤浆氧化制氢研究

利用Fe~(3+)/Fe~(2+)电对的相互转化原理,在水热反应釜中用Fe~(3+)氧化煤浆得到Fe~(2+),将Fe~(2+)在电解槽中电解氧化,在阴极产生氢气,从而通过两步反应形成一个新的煤浆电氧化制氢工艺。进行了九次水热-电解循环实验,在恒电压(1V)条件下,测试了电解反应的电流密度和累积电量的数据,并对循环实验前期、中期、后期的三个阶段煤样品进行了扫描电镜(SEM)、比表面积(BET)、热重(TG)、红外光谱(FT-IR)等表征分析。研究表明,相对于通常煤浆电氧化制氢工艺,这种"两步法"煤浆制氢新工艺具有更高的反应速率,初始电流密度约为60 m A/cm2,而传统的"一步法"煤浆制氢工艺初始电流密度均不超过10 m A/cm~2。表征分析结果很好地反映了煤颗粒在这种制氢工艺过程中的形态、结构、成分的变化,从而解释了在新的煤浆氧化制氢工艺中的Fe~(3+)/Fe~(2+)转化的反应机理。