Reagent optimization for on-line simultaneous polarographic determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of anextremely large excess of Zn^(2+)

Reagents are optimized for the simultaneous determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in zinc sulfate solution, which contains an extremely large excess of Zn^(2+). First, the reagents and their doses for the experiment are selected according to the characteristics of the zinc sulfate solution. Then, the reagent doses are optimized by analyzing the influence of reagent dose on the polarographic parameters(i.e. half-wave potential E_(1/2) and limiting diffusion current I_p). Finally, the optimization results are verified by simultaneously determining trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of an extremely large excess of Zn^(2+). The determination results indicate that the optimized reagents exhibit wide linearity, low detection limits, high accuracy and good precision for the simultaneous determination of trace amounts of Cu^(2+), Cd^(2+) and Co^(2+) in the presence of an extremely large excess of Zn^(2+).

Bifunctional Li6CoO4 serving as prelithiation reagent and pseudocapacitive electrode for lithium ion capacitors

Lithium ion capacitors(LICs)have been widely used as energy storage devices due to their high energy density and high power density.For LICs,pre-lithiation of negative electrode is necessary.In this work,we employ a bifunctional Li6CoO4(LCO)as cathodic pre-lithiation reagent to improve the electrochemical performance of LICs.The synthesized LCO exhibited high first charge specific capacity of 721 mAh g-1and extremely low initial coulombic efficiency of 3.19%,providing sufficient Li+ for the pre-lithiation of negative electrode in the first charge.Simultaneously,Li6–xCoOy is generated from LCO during the first charge process,which exhibits pseudocapacitive property and contributes to capacity in form of surface capacitance during subsequent cycles,increasing the capacity of capacitive positive electrode.With the appropriate amounts of addition to the positive side in LICs,this bifunctional prelithiation reagent LCO shows significantly improved the electrochemical performance with the energy density of 78.5 Wh kg-1after 300 cycles between 2.0 and 4.2 V at 250 mA g-1.

Contacted Ion Pairs in Aqueous CuCl2 by the Combination of Ratio Spectra, Difference Spectra, Second Order Difference Spectra in the UV-Visible Spectra

The microstructure of aqueous CuCl2 has been studied through lots of technologies for many years; however, it remains a controversial subject. In this study, a new spectroscopic method has been proposed to analyze the UV-visible spectra of thin fihn of CuCl2/H2O solutions at different concentrations. This method is the combination of ratio spectra, difference spectra and second order difference spectra. By using this method, two new bands at -230 and -380 nm are obviously observed. The bands are assigned as the contacted ion pairs [CuCl3（H2O）n]- or [CuCl4（H2O）n]2-, which demonstrates that ion pairs exist in the CuCl2/H2O solution. Such finding agrees with the recent theoretical spectra obtained by time-dependent density functional theory. Furthermore, the populations of the contacted ion pairs are discussed. This study not only offers the direct spectroscopic evidence of [CuCl3（H2O）n]- or [CuCl4（H2O）n]2- in aqueous CuCl2, but also suggests that the spec- troscopic analysis method is powerful to extract the weak bands in a strong overlapping spectrum.

Ion Pairing Kinetics Does not Necessarily Follow the Eigen-Tamm Mechanism

The most recognized and employed model of the solvation equilibration in the ionic solutions was proposed by Eigen and Tamm, in which there are four major states for an ion pair in the solution： the completely solvated state, 2SIP （double solvent separate ion pair）, SIP （single solvent separate ion pair）, and CIP （contact ion pair）. Eigen and Tamm suggested that the transition from SIP to CIP is always the slowest step during the whole pairing process, due to a high free energy barrier between these two states. We carried out a series of potential of mean force calculations to study the pairing free energy profiles of two sets of model mono- atomic 1：1 ion pairs 2.0：x and x：2.0. For 2.0：x pairs the free energy barrier between the SIP and CIP states is largely reduced due to the salvation shell water structure. For these pairs the SIP to CIP transition is thus not the slowest step in the ion pair formation course. This is a deviation from the Eigen-Tamm model.

Sympathetic Cooling of ^(40)Ca^(+_27)Al^+ Ion Pair Crystal in a Linear Paul Trap

The 27Al＋ ion optical clock is one of the most attractive optical clocks due to its own advantages such as low black-body radiation shift at room temperature and insensitivity to the magnetic drift. However, it cannot be laser-cooled directly in the absence of 167nm laser to date. This problem can be solved by sympathetic cooling. In this work, a linear Paul trap is used to trap both 40Ca＋ and 27A1＋ ions simultaneously, and a single Dopplercooled 40Ca＋ ion is employed to sympathetically cool a single 27A1＋ ion. Thus a ＇bright-dark＇ two-ion crystal has been successfully synthesized. The temperature of the crystal has been estimated to be about 7mK by measuring the ratio of carrier and sideband spectral intensities. Finally, the dark ion is proved to be an 27Al＋ ion by precise measuring of the ion crystal＇s secular motion frequency, which means that it is a great step for our 2Z Al＋ quantum logic clock.

Chemistry of marine resources——XVI. A new potassium reagent and its enrichment behaviour for potassium ion in seawater

-This paper first presents a new potassium reagent and efficient enrichment agent for direct recovery of potassium from seawater, i. e. , 1, 2, 4, 5-tetrahydroxybenzen -O, O' , O', O'''- tetraacetic acid (TTAH4). The synthetic method of TTAH4, its enrichment behaviour for potassium ion in low concentration solution and seawater, and the chemical structure of its corresponding potassium salt have been investigated. A mechanism which caused the uptake of potassium ion is suggested. Elementary analysis and IR-spectrum determination of the potassium salt proved correct evidence for a polynuclear complex, i. e. , (TTAH3K)n. Thus, the mechanism which caused the uptake of potassium ion may be interpreted in terms of the formation of polynuclear chains as a continual sandwich type coordination complex.

Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations

Ion-pairing high-performance liquid chromatography-ultraviolet （HPLC-UV） methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid （EDTA） in Abilify （a small molecule drug with aripiprazole as the active pharmaceutical ingredient） oral solution and die- thylenetriaminepentaacetic acid （DTPA） in Yervoy （a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient） intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions （Cu2＋, Fe3＋） which generate highly stable metallocom- plexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation in- volving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the de- termination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids （APCAs） including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.

An intravenous clarithromycin lipid emulsion with a high drug loading, H-bonding and a hydrogen-bonded ion pair complex exhibiting excellent antibacterial activity

The aim of this study was to develop an intravenous clarithromycin lipid emulsion(CLE)with good stability and excellent antibacterial activity. The CLE was prepared by the thinfilm dispersed homogenization method. The interaction between clarithromycin(CLA) and cholesteryl hemisuccinate(CHEMS) was confirmed by DSC, FT-IR and^1H NMR analysis. The interfacial drug loading, thermal sterilization, freeze–thaw stability, and in vitro and in vivo antibacterial activity were investigated systematically. DSC, FT-IR and^1H NMR spectra showed that CHEMS(CLA: CHEMS, M ratio 1:2) could interact with CLA through H-bonding and a hydrogen-bonded ion pair. The CHEMS was found necessary to maintain the stability of CLE.Ultracentrifugation showed that almost 88% CLA could be loaded into the interfacial layer.The optimized CLE formulation could withstand autoclaving at 121 °C for 10 min and remain stable after three freeze–thaw cycles. The in vitro susceptibility test revealed that the CLA–CHEMS ion-pair and CLE have similar activity to the parent drug against many different bacterial strains. The in vivo antibacterial activity showed that the ED50 of intravenous CLE was markedly lower than that of CLA solution administrated orally. CLE exhibited pronounced antibacterial activity and might be a candidate for a new nanocarrier for CLA with potential advantages over the current commercial formulation.

The Standard Association Constant of Ion Pair [GaCl]^(2+)in the System of HCl+GaCl_3+H_2O

The standard association constants of ionic pair [GaCl]2+, Kas, were determined by emf(electromotive force) method at 278.15 to 318.15 K. The thermodynamic quantities for the ionic association process were calculated and it was pointed that the association entropy is driving force to form the ionic pair.

Thermodynamics of Ion Pair of Magnesium Sulfate in Mixed Solvent

Introduction Magnesium sulfate is an archetypal 2-2 salt that plays a central role in defining the characteristics of higher valent electrolyte solutions and its solution has been widely used to test various theories of strong electrolyte behavior and to develop models of ion association in solution. Up to now, the ion pairs of magnesium sulfate in an aqueous solution have been widely investigated by using different experimental techniques, such as conductometry , cryoscopy potentiometry solubility and Raman spectrometry. However, to our knowledge, no measurement of the standard association constant of the ion pairs, [ MgSO4 ]^0 in a glucosewater mixed solvent is available.

Ab Initio and DFT Study of Magnesium Sulfate Contact Ion Pairs

The stuctures of contact ion pairs of magnesium sulfate were studied. The geometries of contact ion pairs of MgSO 4(H 2O) n (n =1-6) were optimized by using Hartree Fock (HF/6 31+G *, HF/6 311+G ** ) and density functional theory (DFT) (B3LYP/6 31+G *, B3LYP/6 311+G ** ) methods. The stable structures of monodentate, bidentate and tridentate contact ion pairs were obtained. The bidentate structure of contact ion pairs are the most stable compaired with the monodentate and tridentate ones for the same composition. The hydration enthalpies of contact ion pairs of MgSO 4 (H 2O) n (n =1-4) increase with their hydration numbers.

Novel Properties of Supramolecular Complexes Formed by Pairing Cationic Porphyrin and Anionic Metal-Oxo Cluster

MTBPyP (meso-tetrakis(4-N-benzylpyridyl)porphyrin, M=H-2, Zn) bearing positive charge has been shown to associate with SiW12O404- in water solution. The spectral evolution and Job's plots analyses reveal that the relatively stable aggregates contain equal numbers of MTBPyP4(+) and SiW12O404-.

9－ANTHROIC ACID SENSITIZED PHOTOLYSIS OF DIPHENYLIODONIUM SALTS THROUGH INTRA－ION PAIR ELECTRON TRANSFER

We have studied 9-anthroic acid sensitized photolysis of dipbenyliodonius salts through fluorescence quenching, products analysis and Photo-CIDNP. The photoinduced electron transfer rate constant bas calculated to be 8.6×10 10/mol s. From photo-CIDNP study, both diphenyliodo and pbenyl radicals were confirmed as intermediates. Benzene is a cage escaped product from a singlet radical pair and diphenyliodonium Salt is a recombination preduct from a triplet radical pair.

EPR STUDY OF THE FORMATION OF[Li^+O^-]ION PAIR ON Li-DOPED ZnO

In this letter the study of Li-doped zinc oxide by electron paramagnetic resonance method is described.A signal observed at g_=2.013,g_=1.955 on the degassed sample at 923K was designated to F_s^+ centers(surface oxygen ion vacancies with a single trapped electron).When the sample was quenched from 1003K into liquid oxygen at 77K under 24 KPa O_2,[Li^+O^-] ion pairs valued at g_=2.026 and g=2.003 with superhyperfine constant a=2.0G,which resulted from ~7Li nucleus,formed at Li^+-substitutional site in ZnO lattice.A probable mechanism of [Li^+O^-]ion pair formation was proposed.

INTRA-ION PAIR ELECTRON TRANSFER OF PHOTOEXCITED METHYLENE BLUE BORATE

The photochemical reaction of methylene blue (n-butyltriphenyl) borate, MBRBPh3 was examined. The ultrafast quenching rate and large negative value of Delta G indicated that the intra-ion pair ET plays an important role in photoreaction of MBRBPh3. The sequent boron- carbon bond cleavage of butyltriphenylboranyl radical intermediate was found by GC-MS and photo-CIDNP studies.

Synthesis and Crystal Structure of a Novel Ion-pair Compound Consisting of 1-(4-Bromobenzyl)pyridinium Cation and 7,7,8,8-Tetracyanoquinodimethanide Anion

The title compound [BrBzPy][TCNQ] （BrBzPy^＋=1-（4-bromobenzyl）pyridinium cation, TCNQ = 7,7,8,8-tetracyanoquinodimethanide anion） was synthesized by the reaction of [BrBzPy]Br and LiTCNQ in ethanol solution and its structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P21/c with a = 14.067（3）, b = 7.3089（14）, c = 23.796（4）A, β = 122.011（9）°, V= 2074.6（7）A^3, Z = 4, C24H15BrN5, Mr = 453.32, Dc = 1.451 g/cm^3,μ = 2.002 mm^-1, S = 1.047, F（000） = 916, R = 0.0398 and wR = 0.0921. The most prominent structural features are the completely segregated stacking columns of the TCNQ- anions and [BrBzPy]^＋ cations. In a TCNQ column, the centroid-to-centroid distances of the neighboring anions of TCNQ are 3.2693 and 4.9464 A, respectively.

Synthesis and Crystal Structure of a Novel Ion-pair Compound Consisting of 1,3-Bis(4-cynobenzyl) Imidazole Cation and 7,7,8,8-Tetracyanoquinodimethanide Anion

A novel compound [（CNBz）2Im]2（TCNQ）3（CH3CN）（（CNBz）2Im = 1,3-bis（4-cyano-benzyl） imidazole cation,TCNQ-1 = 7,7,8,8-tetracyanoquinodimethanide anion） was synthesized by the reaction of [（CNBz）2Im]Br and LiTCNQ in water and its structure was determined by single-crystal X-ray diffraction.The crystal belongs to monoclinic,space group P21/c with a = 10.1823（17）,b = 20.292（3）,c = 16.952（3） ,β = 104.73（0）°,V = 3387.6（10）3,Z = 4,C39H24N11,Mr = 646.69,Dc = 1.268 g/cm3,μ = 0.080 mm-1 and F（000） = 1340.The structure was solved by direct methods and refined to R = 0.0596 and wR = 0.0911 for 2690 observed reflections（Ⅰ 〉 2σ（Ⅰ））.The most prominent structural feature is that there are two types of TCNQ entries（TCNQ-1 and TCNQ0） in agreement with the IR spectra analysis of the compound.

Synthesis and Crystal Structure of an Ion-pair Compound: [H_2(teta)]^(2+)·[Ni(CN)_4]^(2-)·2H_2O (teta = Meso-5,7,7,12,14,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane)

The ion-pair compound [H2（teta）]^2＋·[Ni（CN）4]^2-·2H2O （C20H42N8NiO2, teta = meso- 5,7,7,12,14,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane） was synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P211n with a = 10.0784（10）, b = 9.5411（7）, c = 14.1010（14）А, β= 106.752（2）°, V= 1298.4（2）A^3, Mr = 485.33, Z= 2, De= 1.241 g/cm^3,μ（MoKα） = 0.778 mm^-1 and F（000） = 524. The structure was refined to R = 0.0391 and wR = 0.0870 for 2614 observed reflections with I 〉 2σ（I）. The title compound contains one [Ni（CN）4]^2- anion, one protonated macrocyclic tetraamine cation [H2（teta）]^2＋ and two water molecules. There are multiform hydrogen bonds in the compound to link the different components and stabilize the crystal structure.

The Kadomtsev-Petviashvili equation for dust ion-acoustic solitons in pair-ion plasmas

Using the reductive perturbation method,we have derived the Kadomtsev-Petviashvili（KP） equation to study the nonlinear properties of electrostatic collisionless dust ion-acoustic solitons in pair-ion（p-i） plasmas.We have chosen the fluid model for the positive ions,the negative ions,and a fraction of static charged（both positively and negatively） dust particles.Numerical solutions of these dust ion-acoustic solitons are plotted and their characteristics are discussed.It is found that only the amplitudes of the electrostatic dust ion-acoustic solitons vary when the dust is introduced in the pair-ion plasma.It is also noticed that the amplitude and the width of these solitons both vary when the thermal energy of the positive or negative ions is varied.It is shown that potential hump structures are formed when the temperature of the negative ions is higher than that of the positive ions,and potential dip structures are observed when the temperature of the positive ions supersedes that of the negative ions.As the pair-ion plasma mimics the electron-positron plasma,thus our results might be helpful in understanding the nonlinear dust ion acoustic solitary waves in super dense astronomical bodies.

Novel additives for the separation of organic acids by ion-pair chromatography

This paper proposes the use of novel surfactant additives for the separation of organic acids by ion-pair chromatography and studies the influences of surfactants on the chromatographic separation behaviors.Researches have been carried out on both silica gel matrix and polymer supporters in order to compare the two ordinary kinds of stationary phases,and the phenomenon is similar. Separation is based on differences in the stabilities of analyte-additive complexes in solution.Retention times of analytes can ...