Macrocyclic compound as ionophores in lead(Ⅱ) ion-selective electrodes with excellent response characteristics

Macrocyclic compounds,such as crown ethers,azacrown ethers,thiacrown ethers,calixarenes and porphyrins,which act as ionophores in lead(Ⅱ) ion-selective electrodes,are systematically summarized based on the latest literatures.The molecular structure characteristics of the ionophores are general-ized.The modification regulations for the substituted ionophores are elaborated with the purpose of improving the response features of the lead(Ⅱ) ion-selective electrodes assembled by them.It is pointed out that the introduction of pendant moieties which contain soft base coordination centers like N,S and P atoms is in favor of adjusting the cavity size and conformation of the macrocyclic com-pounds.Furthermore,there is synergic effect between the cavity and the donor sites of the ligand and thus the selective complexation of lead ions is easily realized,resulting in significant avoidance of the interference from other metal ions.The macrocyclic ionophore having the best response characteris-tics thus far was found to be N,N'-dimethylcyanodiaza-18-crown-6 with the detection limit of 7.0×10-8(14.5 μg/L),which is one of the uncommon ionophores that can really eliminate the interference from silver and mercury ions.The selectivity coefficients of the ionophore for lead ions over other metal ions,such as alkali,alkaline earth and transition metal ions are in the order of 10-4 or smaller,where the se-lectivity coefficient of lead(Ⅱ) over mercury(Ⅱ) ions is much lower,down to 8.9×10-4.The structure de-sign idea for high-performance ionophore is proposed according to present results.The incorporation of nitrogen atom,especially cyano group or thiocyano group or amino/imino groups,rather than thio atom alone could result in new excellent lead ionophores.The aborative design for metacyclophanes containing aromatic nitrogen atoms with the aim of creating excellent ionophores would also become a potential research trend.The lead(Ⅱ) ion-selective electrodes have shown widely potential applications in the potentiometric titration,and flow injection potentiometry,and in the direct determination of lead in stack emissions of lead smelters,and assay of lead in rocks,particularly in the direct measurements of trace amount of lead(Ⅱ) in human hair,blood,edible oil,food,water,and air.     

Acetone hydrogenation in exothermic reactor of an isopropanol–acetone–hydrogen chemical heat pump: effect of intra-particle mass and heat transfer

Intra-particle mass and heat transfer plays an important role in performance of the exothermic fixed-bed reactor for an isopropanol-acetone-hydrogen chemical heat pump. In this work, an exothermic fixed-bed reactor model, taking into account the actual packing structure, is established in the commercial software Fluent. A 120° segment of a tube with tube-to-particle diameter ratio （n） of 4, where realistic particles are packed and set to porous media, is used to simulate the 3D external flow, concen- tration and temperature fields in the exothermic packed-bed reactor. The influence of catalyst particle diameter （dp） and micropore diameter （do） on the intra-particle temperature, species distribution, reaction rate and selectivity is dis- cussed. The appropriate dp and do are obtained. Simulation results showed that intra-particle temperature gradient is not obvious. Large dp and small do lead to remarkable gradient of reaction rate inside the catalyst particle and the decrease in the catalyst efficiency and reduce the acetone conversion and the selectivity in isopropanol. The optimal results reveal that the spherical catalyst with dp of 1 mm and dpore of 10 nm is appropriate for high-temperature acetone hydrogenation.     

Review on aggregation of acid extractants in solvent extraction of metal ions: remark on the general model

The aggregation behavior of various acid extractants in the solvent extraction systems of metal ions is re-examined and explained according to knowledge obtained in recent work. The conclusions are as follows. (1) Complexes formed by the extractants and metal ions can form reversed micelles in organic diluents, depending on the microstructures of the complexes. The dimers of the acid extractant cannot percolate to the metal-extractant aggregates, and the acid-salt complexes are always formed in the aggregates. The reversed micelles or the W/O microemulsions formed by different species cannot be associated with each other to form a unified aggregate. (2) In solvent extraction systems, hydration of the extractants and metal ions can be considered as the driving force of forming reversed micelles. (3) Information of the first approach to the insight of the bicontinuous microemulsion of NaDEHP shows that various components in the aqueous phase behave confined and very similar to the typical AOT/n-heptane W/O microemulsions. (4) In the extraction of lanthanide ions by the W/O microemulsion of sodium naphthenate, the saponification is a process of forming reversed micelle or W/O microemulsion, while the extraction step is a process of destroying reversed micelles or W/O microemulsion droplets.     

Fluorescence quenching effect of metal ions for α,α''''-diamine containing conjugated polymers in solid films

The fluorescence quenching effect of the conjugated polymers P1 and P2 (the molecular recognitions are twisted 2,2'-bipyridine (bpy) and planar 1,10-phenanthrolin (phen), respectively) films upon the addition of metal ions has been studied. And the results showed that P2 exhibited stronger fluorescence quenching ability upon the addition of both transition metal ions and main group metal ions compared with that of P1. The 20° twist angle between the two consecutive pyridine rings of bpy unit in the P1 main chain is the reason for the weaker fluorescence quenching ability compared with P2, in which the planar phen unit can chelate with metal ions relatively freely without the conformational transition. So P2 is a kind of material with better properties for solid film devices, such as sensors for metal ions recognition.     

Discussion of an Enrichment Mechanism of Precious Metals by Base Metals and Mattes in Pyrometallurgical Processes

The enrichment mechanisms of precious metals by base metals or their mattes in pyrometallurgical processes are discussed at the atomic level in this paper. The reasons brought forward for a trace amount of precious metals to be trapped into base metals or mattes are that the melted slag phases possess different chemical structures and properties from that of the melted base metal or matte phases. As for the melted slag phase, its formation is thought to depend on the covalent bonds and the ionic bonds between Si, O atoms and Ca2+, Mg2+, Fe2+ ions to tie up each other. Because the bridging electrons in the slag phase are all thought as the localized electrons, the precious metal atoms are not stable among them. However, as for the metal phase, its formation is thought depend on the metal bonds to bind up the metal atoms. Because the electrons in the metal phases can move freely among the atoms, the precious metal atoms that enter the metal phase can cause the system’s free energy to decrease. For the melted mattes phase,because it has high electrical conductivities (between 103～104 s·cm-1) at higher temperatures, and its temperature coefficients presents the negative values, its conductance mechanism belongs with the electronic conduction. The property of the mattes is in fact similar to that of the metal at their melted state, so the precious metal atoms will enter the matte phase instead of the slag phase in a mattesmelting process.     

Mercury pollution in Rana Chensinensis in Weisha River reach, in the upstream region of Songhua River

Twice a year continuous samples of Rana Chensinensis and sediments have been collected near gold mine in the upstream region of Songhua River from 2000 to 2002, for analyzing the total mercury （THg）, methylmercury （MeHg） concentration and correlation in sediments, muscles, livers of the frog. The study indicates that THg and MeHg concentrations in polluted samples near the gold mine are higher than those in unpolluted ones. THg and MeHg con- centrations are higher in autumn, in female, and in livers than those in spring, in male, in muscles respectively. The order of concentration degree in the frog organizations is as follows： liver〉muscle〉ovum〉Fallopian tube. MeHg is the main form of mercury （Hg） existing in autumn, while inorganic Hg is in spring. There is no distinct difference of CMeHg/CTHg between male and female, livers and muscles. The correlation between MeHg concentrations in the river sediments and in the frog＇s livers and muscles are significant, which is related to disorderly discharge of Hg.     

Synthesis of Novel Metal Ion Sensors Based on DNA-Metal Interactions

The interactions of metal ions with nucleic acids, nucleosides, and nucleo-bases have been extensively investigated .We have reported that thymine-thymine （T-T） and cytosine-cytosine （C-C） miss base pairs in DNA duplexes highly selectively capture Hgn ion and AgI ion, which result in formations of metal-mediated base pairs, T-Hg^Ⅱ -T and C-Ag^Ⅰ -C, in duplexes. The phenomenon is expected to be useful for a variety of studies such as synthesis of nano-wires containing metal ions, developing metal-ion sensing methods, etc. Here, we report novel oligodeoxyribonucleotide （ODN）-based sensors that detect Hgn ions and Ag^Ⅰ ions in aqueous solutions.     

Applications of graphene-based materials in environmental protection and detection

Many efficient adsorbents and sensors based on graphene and functionalized graphene have been constructed for the removal and detection of environmental pollutants due to its unique physicochemical properties. In this article, recent research achievements are reviewed on the application of graphene-based materials in the environmental protection and detection. For environmental protection, modified graphene can adsorb heavy metal ions in a high efficiency and selectivity, and thus reduces them to metals for recycling. High adsorption capacity of graphene-based materials to kinds of organic pollutants in water was also presented. Several graphene-based sensors with high limit of detection were reported to detect heavy metal ions, toxic gases and organic pollutants in environment. Finally, a perspective on the future challenge of adsorbents and detection devices based on graphene is given.     

羟基化石墨烯量子点作为灵敏检测金属离子的荧光探针

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater. Here, we developed a new probe for the determination of metal ions by fluorescence quenching. The probe consists of hydroxylated graphene quantum dots (H-GQDs), prepared from GQDs by electrochemical method followed by surface hydroxylation. It is a non-reactive indicator with high sensitivity and detection limits of 0.01 μM for Cu2+, 0.005 μM for Al3+, 0.04 μM for Fe3+, and 0.02 μM for Cr3+. In addition, the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.     

Palladium（ Ⅱ ） and Platinum（ Ⅱ ） Compounds Derived From Potentially Terdentate Ligands

Transition metal complexes derived from potentially terdentate ligands have attracted great interest in the late years. Among all the examples described so far, those containing palladium（ Ⅱ ） or platinum（ Ⅱ ） and ligands holding three heteroatoms with different donor abilities are particularly relevant. In compounds of this kind, the potential hemilability of one of the terminal σ（M-donor atom） bonds, plays an important role in the view of their applications in homogeneous catalysis. On the other hand, it is well-known that in dimetallic complexes the presence of two different metals in a close vicinity may influence their mutual cooperation in a wide variety of processes. Besides that, some examples of the utility of chiral palladium（ Ⅱ ） as well as platinum（ Ⅱ ） complexes as precursors for organic and/or organometallic synthesis, as chiral recognitors or discriminators, or even in Bio-Medicine have also been reported. However, chiral heterodimetallic compounds holding ferrocenyl units and potentially terdentate ligands are scarce.     

Synthesis and structure of Cu5(BTA)6(TTA)4 · 5DMF, a copper-nitrogen cluster containing η Π3-benzotriazolate

The title cluster compound—Cu₅(BTA)₆(TTA)₄·5DMF was prepared using thenyltrifluoroacetone and benzotriazolate ligands. The crystal structure indicates that a tetrahedral array of Cu(1), Cu(2), Cu(3) and Cu(4) ions surrounding a central Cu(5) ion are held together by bridging tridentate BTA^- and terminated by TTA^- bond cap. The three nitrogen atoms of a BTA^- bond three different copper ions to form a η³-benzotriazolate. The central Cu ion has a distorted octahedral structure and the surrounding Cu ions are 5 coordinated forming distorted tetragonal structures. The distances between the surrounding Cu(Ⅱ) ions and the central Cu(Ⅱ) ion are in the range of 0.3561—0.3755 nm and those between the surrounding Cu(Ⅱ) ions are in the range of 0.5785—0.6301 nm.     

Sensitive Determination of DNA by RLS Enhancement of Metal Ions

0　IntroductionThequantitativeanalysisofnucleicacids,especiallythemi cro determinationofnucleicacids,isbecomingmoreandmoreimportantinmanybiologicalstudies.Recently ,apromisingspectraltechnique ,whichwasbasedonthemeasurementofen hancedresonancelightscattering (RLS) [1 ,2 ] ,hasgivenrisetostronginterestbyanalystsandbiochemistsfornucleicacidsandproteinassay[3 9] .Uptonow ,manykindscompoundshavebeenfoundRLSenhancementwhilebindingtoDNA ,andallthesecompoundsarecharacterizedofpositivechargewhicha…     

酰胺型三脚架化合物作为离子选择性电极载体的比较研究

研究了以5种新型酰胺型三脚架有机化合物为载体的PVC膜电极对碱金属和碱土金属阳离子的响应行为。比较了，这5种三脚架化合物的结构对电极响应性能的影响。结果表明，不含较大萘环的配体适于作为离子选择电极的载体，所制电极可作为Li^ 或Ca^2 选择性电极，当电极膜中增塑剂的极性较大时，有利于电极对二价离子的响应，若配体中基团的体积较大时，则不利于配体对金属阳离子的络合及所形成络合物在膜相中的流动。     

Electrochemical determination of trace amounts of lead (II) and cadmium (II) at a calix[6]arene modified carbon paste electrode

An electrochemical method for the simultaneous determination of lead(II) and Cadmium(II) with a calix[6]arene modified carbon paste electrode (CPE) has been developed. Pb²⁺ and Cd²⁺ were accumulated at the surface of the modified electrode via formation of chemical complexes with calix[6]arene, and reduced at 1.40 V. During the following anodic potential sweep, reduced lead and cadmium were oxidized, and two well-defined striping peaks appeared at about −0.60 V and −0.84 V. Compared with a bare carbon paste electrode, the calix[6]arene modified CPE greatly improves the sensitivity of determining lead and cadmium. The stripping peak currents change linearly with the concentration of Pb²⁺ 3.0×10⁻⁸–8.0×10⁻⁶ mol·L⁻¹ and with that of Cd²⁺ 6.0×10⁻⁸–1.0×10⁻⁵ mol ·L⁻¹. The detection limits of Pb²⁺ and Cd²⁺ are found to be 8.0×10⁻⁹ mol·L⁻¹ and 2.0×10⁻⁸ mol·L⁻¹, respectively. The modified carbon paste electrode was applied to determine trace levels of lead and cadmium in water samples. Comparing with that of atomic absorption spectrometry, the results suggests that the calix[6]arene modified CPE has great potential for the practical sample analysis. Foundation item: Supported by the National Natural Science Foundation of China (60171023) Biography: JI Xiao-bo (1980-), male, Master, research direction: electroanalytical chemistry.     

Determination of trace heavy metals in milk using an ionic liquid and bismuth oxide nanoparticles modified carbon paste electrode

A novel carbon composite electrode modified with bismuth oxide nanoparticles and the ionic liquid n-octylpyridinium hexafluorophosphate was fabricated and used to simultaneously determine cadmium and lead levels using square wave anodic stripping voltammetry.This electrode combines the unique advantages of nanomaterials and ionic liquid with the low cost and easy fabrication of the carbon composite electrode.Compared with the traditional binder based composite electrode,our electrode exhibited well-defined and separate stripping voltammetric peaks for cadmium and lead.Furthermore,the antifouling capacity of the bismuth film electrode was significantly improved by the ionic liquid.Under optimized conditions,the linear range of the composite electrode was from 3.0 to 30.0 μg L-1 for both metal ions with a detection limit of 0.15 μg L-1 for cadmium and 0.21 μg L-1 for lead.Trial milk sample analyses showed that the modified electrode was sensitive,reliable and effective for the determination of trace heavy metals,holding great promise for routine analysis applications.     

Measurement of trace lead (II) in water samples with biomacromolecule heparin modified electrode

A new method for electrode modification and accumulation with a biomacromolecule and subsequent voltammetric quantittion of metal ions is described. Heparin is used as the surface modifier, and the method is based on formation of the heparin complex of lead (II). The voltammetric responses were evaluated with respect to electrolyte, pH, preconcentration time, and lead concentration. The electrode composition, voltammetric wave form and other variables have also been taken into account. A detection limit of 3.0×10⁻⁹ mol/L has been obtained by preconcentration for 20 min. The method is sensitive, simple and relatively rapid, with a relative standard deviation of 5.2% at the 1.0×10⁻⁷ mol/L level. Supported by the Trants-Century Training Program Foundation for the Talents from the State Commission of Education of China: the national Natural Science Foundation of China and the Opening Laboratory Foundation of Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. Li Huiling: Born in July 14, 1972. Master of Science.     

Supermolecular layered double hydroxides

Research progresses in the layered double hydroxides [M _(1-x ^)/2+ M _x ³⁺ (OH)₂] ^x+ A _x ^n/n− ·mH₂O intercalated with metal coordinate ions or oxometalates in the last ten years are reviewed. These layered double hydroxides are mainly intercalated with polyoxometalate (POM) ions, a LiAl-LDH photochemical assembly containing TiO₂ and CH₃(CH₂)₁₂COO⁻ anions, together with Zn(TPPC) (porphyrin derivate) and macrocyclic ligand-containing porphyrin derivate anions. Emphasis is put on the synthesis methods for intercalation of the anions into the interlayer regions, the characterization techniques and structures for the layered compounds and the newest research progress in the fields such as catalysis. The review also forecasts the prospects of the field.     

Effects of anions on the biosorption of microelement cations by macroalga <Emphasis Type="Italic">Enteromorpha prolifera</Emphasis> in single- and multi-metal systems

The results of research on the effects of anions on the biosorption of microelement cations by the edible marine macroalga Enteromorpha prolifera in singleand multi-metal systems are discussed in this paper. It was shown that the maximum biosorption capacity (qmax) in a single-metal system of Co(II) ions decreased in the following sequence: Cl- (46.0 mg g-1) > SO42- (42.8 mg g-1) > NO3- (41.9 mg g-1). In multi-metal systems, in which the ratios of Cl-, NO3-, and SO42- were 0:0:4, 1:1:2, 3:0:1, and 4:0:0, there were clear differences among the biosorption capacities. In all the examined systems (other than the 0:0:4 system), inhibition of the binding of microelement cations by the macroalga was observed. In all the systems, the highest value of qmax was obtained for Cu(II) cations; the value ranged from 31.9 mg g-1 in 0:0:4 (SO42- only) to 18.2 mg g-1 in 4:0:0 (Cl-only).     

Adrenomedullin inhibits the endothelin production induced by urotensin II in rat vascular smooth muscle cells

The aim of this study was to observe the effects of adrenomedullin (ADM) on endothelin (ET) production induced by urotensin Ⅱ (UⅡ) in rat vascular smooth muscle cells (VSMCs). Cultured VSMCs which were incubated with UⅡ (10^-8 mol/L) and with various concentrations of ADM were used to measure the VSMCs ³H-TdR incorpora- tion, the activity of extracellular signal-regulated kinase (ERK), the amount of ET mRNA and ET production in VSMCs. In this work we found that incubation with UⅡ(10^-8 mol/L) increased obviously the amount of ET mRNA in VSMCs and ET production in medium, however, coincubation with ADM (10^-10—10^-8 mol/L) and UⅡ(10^-8 mol/L) reduced the amount of ET mRNA by 15%, 24% and 45% (P< 0.01) respectively, compared with UⅡ alone. The content of ET in medium was 14.13, 11.38 and 11.00 pg/mL. ADM alone (10^-8 mol/L) had no effect on ET production in VSMCs. UⅡ (10^-8 mol/L) promoted the 3H-TdR incorpo- ration and activity of ERK in VSMCs. ADM inhibited VSMCs 3H-TdR incorporation and activation of ERK in a concentration-dependent manner. Compared with UⅡ group, after coincubation with ADM (10^-10—10^-8 mol/L) and UⅡ (10^-8 mol/L) the VSMCs 3H-TdR incorporation was decreased by 7% (P > 0.05), 32% (P < 0.05) and 41% (P < 0.01), respectively, and the activity of ERK was decreased by 24% (P > 0.05), 32% (P < 0.05) and 36% (P < 0.05), re- spectively, in a concentration-dependent manner. The results show that in cultured VSMCs ADM inhibits ET mRNA expression, ET production and proliferation stimulated by UⅡ, and that inhibitory effect of ADM on UⅡ bioaction could be mediated through inhibiting MAPK pathway.     

Synthesis and X-ray crystal structure of a new manganese 18-metallacrown-6

0　IntroductionThemetalionsinmetallamacrocylesformedbysupramolecularself assemblycantaketrigonal,square planar,andtetrahe dralconfiguration[1 ,2 ] .Metallacrownisaspecialclassofmetalla macrocyle,theyareanalogoustocrownethersinbothstructureandfunctionexceptthatthemetalionsarenowtakingthepositionsofcoordinationatomsincrownether[3,4] .Themetallacrownswithdifferentnumberof [M—N—O]repeatunithavedifferentcavitysizes,suchas 9 MC 3[5 7] ,12 MC 4 [4,8 1 4 ] and 15 MC 5 [1 5] .Thereportedazameta…