Effects of divalent metal ions on electrochemiluminescence sensor with Ru(bPY)(3)(2+) immobilized in Eastman-AQ membrane

Different effects of divalent metal ions on electrochemiluminescence (ECL) sensor with Ru(bPY)(3)(2+) immobilized in Eastman-AQ membrane were investigated. Mg2+,Ca2+ and Fe2+ can elevate the ECL of Ru(bpY)(3)(2+)/proline; while metal ions that underwent redox reactions on the electrode such as Mn2+ and Co2+ presented intensive quenching effects on Ru(bpy)(3)(2+) ECL. Also, the quenching effect of Mn2+ on the ECL sensor with Ru(bpY)(3)(2+) immobilized in Eastman-AQ membrane enhanced to about 30-folds compared with the case that Ru(bpy)(3)(2+) was dissolved in phosphate buffer, and the enhanced quenching effects of Mn2+ were studied.

Adsorption studies of divalent metal ions with extraction resin containing 1-hexyl-4-ethyloctyl isopropylphosphonic acid

Equilibrium distributions of cobalt(II), nickel(II), zinc(II), cadmium(II), and copper(II) have been studied in the adsorption with extraction resin containing 1-hexyl-4-ethyloctyl isopropylphosphonic acid (HEOPPA) as an extractant from chloride medium. The distribution coefficients are determined as a function of pH. The data are analyzed both graphically and numerically. The extraction of the metal ions can be explained assuming the formation of metal complexes in the resin phase with a general composition ML2(HL)(q). The adsorbed species of the metal ions are proposed to be ML2 and the equilibrium constants are calculated. The efficiency of the resin in the separation of the metal ions is provided according to the separation factors values. The separation of Zn from Ni, Cd, Cu, Co, and Co from Ni, Cd, Cu with the resin is determined to be available. Furthermore, Freundlich's isothermal adsorption equations and thermodynamic quantities, i.e., DeltaG, DeltaH, and DeltaS are determined.

Solvent extraction of scandium(III), yttrium(III), lanthanides(III), and divalent metal ions with sec-nonylphenoxy acetic acid

Such physicochemical properties of sec-nonylphenoxy acetic acid (CA-100) as the solubility in water, acid dissociation constant in water, dimerization constant in heptane, and distribution constant in organic solvent-water were measured by two-phase titration. The extraction behaviors of scandium (III), yttrium (III), lanthanides (III), and divalent metal ions from hydrochloric acid solutions with CA-100 in heptane have been investigated, and the possibilities of separating scandium (yttrium) from lanthanides and divalent metal ions have been carefully discussed. The stoichiometries of the extracted metal complexes were investigated by the slope-analysis technique. The effect of the nature of diluent on the extraction of yttrium (III) with CA100 has been studied and correlated with the dielectric constant.

FT-RAMAN SPECTROSCOPIC STUDIES ON THE INTERACTION OF METAL-IONS WITH SPHINGOMYELIN BILAYER

The interaction of trivalent lanthanide ions and divalent calcium ions with sphingomyelin bilayer has been studied by FT-Raman spectroscopy. The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bilayer, either La3+ or Ca2+, did not change the conformation of the choline group, that is, O-C-C-N+ is still in its gauche conformation. The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline. They increased the fluidity of acyl chains of sphingomyelin bilayer and made them packed disorderly.

EFFECTS OF METAL-IONS ON THE CONFORMATION OF POLAR HEADGROUP OF SPHINGOMYELIN BILAYER

With the wide application of rare earth in agriculture, medicament, especially the application of Gd-DTPA as nuclear magnetic resonance image reagent in clinical practice([1]), the studies on the toxicology in biological body, as well as the study on the use as informative probes instead of divalent calcium ion in biological and biochemical research have attracted intensive concern([2]). Phospholipids bilayers have served as a model of biomembrane in the last two decades. The effects of metal ions on the conformation of polar headgroup of dipalmitoylphosphatidylcholine (DPPC) bilayers have been reported([3]). Sphingomyelin is major component of several biological tissues such as brain and nerve cells and has identical polar headgroup to DPPC. The interaction of metal ions with sphingomyelin bilayer remains nonrevealed. This note presents the results of the study on this aspect.

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Isolated transition metal ions/oxides in molecular sieves and on surfaces are a class of active sites for selective oxidation of hydrocarbons. Identifying the active sites and their coordination structure is vital to understanding their essential role played in catalysis and designing and synthesizing more active and selective catalysts. The isolated transition metal ions in the framework of molecular sieves (e.g., TS-1, Fe-ZSM-5, and V-MCM-41) or on the surface of oxides (e.g., MoO3/Al2O3 and TiO2/SiO2) were successfully identified by UV resonance Raman spectroscopy. The charge transfer transitions between the transition metal ions and the oxygen anions are excited by a UV laser and consequently the UV resonance Raman effect greatly enhances the Raman signals of the isolated transition metal ions. The local coordination of these ions in the rigid framework of molecular sieves or in the relatively flexible structure on the surface can also be differentiated by the shifts of the resonance Raman bands. The relative concentration of the isolated transition metal ion/oxides could be estimated by the intensity ratio of Raman bands. This study demonstrates that the UV resonance Raman spectroscopy is a general technique that can be widely applied to the in-situ characterization of catalyst synthesis and catalytic reactions. (C) 2003 Elsevier Science (USA). All rights reserved.

Binding of metal ions with protein studied by a combined technique of microdialysis with liquid chromatography

A method has been developed for the determination of interactions of metal ions and protein by using microdialysis sampling technique combined with pre-column derivation and reversed-phase ion-pair liquid chromatographic (HPLC analysis. Cu(II), Zn(II) and human serum albumin (HSA) were chosen as model metal ions and protein, respectively. The mixed solutions of metal ions and HSA with different molar ratios buffered with 0.1 M Tris-HCl containing 0.1 M NaCl at pH 7.43 were sampled with a mirodialysis probe by keeping perfusion rate at 1 mul/min and the temperature at 37 degreesC. The free concentrations of metal ions in microdialysates were assayed by precolumn derivatization with meso-tetra(4-sulfophenyl)-porphyrin (TPPS4) followed ion-pair HPLC analysis. The recovery (R) of microdialysis sampling was measured in vitro under similar conditions as 65.74% for Cu(II), 70.45% for Zn(II) with R.S.D. below 3.2%. The primary binding constants and number of binding site estimated by the Scatchard plot analysis are 5.04 x 10(6) M-1 and 0.85 for Cu(II), and 9.87 x 10(6) M-1 and 1.10 for Zn(II), respectively. The competition of Cu(II) and Zn(II) at the second binding site on HSA was investigated, and it was observed that there is a second site on HSA to bind Cu(II) and Zn(II), the affinity of Cu(II) is stronger than that of Zn(II) to this second site of HSA. (C) 2001 Elsevier Science B.V. All rights reserved.

Competing binding of metal ions with protein studied by microdialysis

A method has been established to study the competing binding of metal ions with protein by a combined technique of microdialysis with high performance liquid chromatography (HPLC). Ni2+, Cd2+, Zn2+, Cu2+ and human serum albumin (HSA) were chosen as model metal ions and protein. The experimental results show that Ni2+ and Cu2+ share a common primary binding site on HSA, and Zn2+ and Cd2+ share a different common primary binding site from them, but there is a common multi-metal binding site for all of those four metal ions. This method show advantages of fast sampling, easily to be operated and especially to be useful when ideal spectroscopic probes are not available for the study of interaction between protein and metal ions.

functional monomers and polymers.CXXXVI.effect of metal ions on the interaction of synthetic nucleic acid analogs

The effect of metal ions on the conformation of thymine-containing poly-D-lysine was studied by CD spectra in aqueous solution. Of the metal ions studied,only copper(Ⅱ)ion affected the conformation of mucleic acid analogs .copper(Ⅱ)ion also affected the specifically interacting system made up of thymine-containing poly-D-lysine and polyadenylic acid.

An effective method for enhancing metal-ions' selectivity of ionic liquid-based extraction system: Adding water-soluble complexing agent

Selective extraction-separation of yttrium(Ill) from heavy lanthanides into 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)mim][PF6]) containing Cyanex 923 was achieved by adding a water-soluble complexing agent (EDTA) to aqueous phase. The simple and environmentally benign complexing method was proved to be an effective strategy for enhancing the selectivity of [C(n)mim] [PF6]/[Tf2N]-based extraction system without increasing the loss of [C(n)mim](+). (c) 2007 Elsevier B.V. All rights reserved.

Chitosan(Chitin)/Cellulose Composite Biosorbents Prepared Using Ionic Liquid for Heavy Metal Ions Adsorption

Chitosan(chitin)/cellulose composites as biodegradable biosorbents were prepared under an environment-friendly preparation processes using ionic liquids. Infrared and X-ray photoelectron spectra indicated the stronger intermolecular hydrogen bond between chitosan and cellulose, and the hydroxyl and amine groups were believed to be the metal ion binding sites. Among the prepared biosorbents, freeze-dried composite had higher adsorption capacity and better stability. The capacity of adsorption was found to be Cu(II) (0.417 mmol/g) > Zn(II) (0.303 mmol/g) > Cr(VI) (0.251 mmol/g) > Ni(II) (0.225 mmol/g) > Ph(II) (0.127 mmol/g) at the same initial concentration 5 mmol L-1. In contrast to some other chitosan-type biosorbents, preparation and component of the biosorbent were obviously more environment friendly. Moreover, adsorption capacity of chitosan in the blending biosorbent could be fully shown.

Surface plasmon resonance and electrochemistry for detection of small molecules using catalyzed deposition of metal ions on gold substrate

Small molecules are difficult to detect by conventional surface plasmon resonance (SPR) spectroscopy due to the fact that the changes in the refractive index resulted from the binding process of small biomolecules are quite small. Here, we report a simple and effective method to detect small biomolecule using SPR spectroscopy and electrochemistry by catalyzed deposition of metal ions on SPR gold film. As an example, the ascorbic acid-mediated deposition of Ag on gold film was monitored by in situ SPR spectrum. The deposition of Ag atom on gold film resulted in an obvious decrease of depth in SPR angular scan curves of reflectance intensity and minimum reflectivity angle. The depth change of the SPR reflectance intensity and minimum reflectivity angle curves mainly relied on the amount of Ag atom deposited on gold film that can be controlled by the concentration of ascorbic acid. By monitoring the deposition of Ag atom on gold film, ascorbic acid was detected in the concentration range of 2 x 10(-5) M to 1 x 10(-3) M. After each of detections, the SPR sensor surface was completely regenerated by a potential step that stripped off the Ag atom. Furthermore, the regeneration process of the sensor surface provides the feasibility for detecting the concentration of ascorbic acid by electrochemical method.

Application of room temperature ionic liquid-based extraction for metal ions

As a kind of novel green solvent, Room Temperature Ionic Liquids (RTILs) have been paid ever-increasing attentions in RTIL-based extraction for metal separation, since they have many unique proper-ties, such as non-volatile and non-flammable. The progress of that is mainly composed of the partition properties, mechanisms, defects, overcome methods and forecasts of the processes on the environmental analytical chemistry, has been reviewed.

Electrochemical recognition of alkali metal ions at the micro-water 1,2-dichloroethane interface using a calix[4]arene derivative

In this paper, a calix[4]arene derivative, 5,11,17,23-butyl-25,26,27,28-tetra-(ethanoxycarbonyl)-methoxy-calix[4]arene (L), is investigated as a host to recognize alkali metal ions (Li+, Na+, K+, Rb+ and Cs+) at the interface between two immiscible electrolyte solutions (ITIES). Well-defined cyclic voltammograms are obtained at the micro- and nano-water \ 1,2-dichloroethane (W \ DCE) interfaces supported at micro- and nano-pipets.