Facilitated transport of Hg(II) through novel activated composite membranes

The results presented in this work deal with the prime application of activated composite membranes (ACMs) for the transport of Hg(II) ions in a continuous extraction–re-extraction system using di-(2-ethylhexyl)dithiophosphoric acid (DTPA) as carrier. The effects of variables such as the pH, the nature of the acid and the concentration of the casting solutions on the transport of Hg(II) are also investigated. When the ACM was prepared with a 0.5 M DTPA solution and when the feed solution contained 2.5×10^–4 M Hg(II) in 0.1 M HCl, the amount of mercury extracted was greater than 76%. The re-extracted mercury was subsequently recovered by means of a stripping phase comprising 0.3 M thiourea solution in 2 M H₂SO₄, yielding 54% of the initial amount of mercury after transport had taken place for 180 min.     

Simultaneous determination of DTPA,EDTA, and NTA by capillary electrophoresis after complexation with copper

We present a method for simultaneous determination of the aminopolycarboxylic acids DTPA, EDTA and NTA in dishwashing detergents, paper mill waters, and natural waters by capillary electrophoresis (CE). The complexing agents were examined as their copper(II) complexes and separated by conventional CE with reversed polarity of the applied voltage. The optimum separation conditions were established by varying the pH and phosphate and tetradecyltrimethylammonium bromide (TTAB) concentrations in the run buffer. The separations were carried out in a fused-silica capillary (61 cm×75 m i.d.) filled with phosphate buffer (80 mmol L^–1, TTAB concentration 0.5 mmol L^–1, pH 7.1, voltage –20 kV) using direct UV detection at 191 and 254 nm. With this CE method all the peaks in the electropherograms were properly separated, the calibration plots gave good correlation coefficients and all three complexing agents could be detected in less than 4 min. Linear calibration plots were obtained for CuDTPA, CuEDTA and CuNTA; limits of detection were 0.03 mmol L^–1 for all complexing agents and recoveries for all tested samples were within the range 104±7%. Results obtained from dishwashing detergent samples were found to be reliable and comparable with those from HPLC (R²=0.989) and UV–Vis (R²=0.985) methods.     

2-十四烷基-DTPA及其钆(Ⅲ)螯合物的合成与表征(英)

Synthesis and characterization of the ligand, [2-tetradecyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, H₅L] and its Gd(Ⅲ) chelate are described. Protonation constants for H₅L (lgK_i^H = 10.80, 8.40, 4.30, 2.80, 2.15) and the stability constant for GdL^2- (lgK_GdL^2-= 22.75) were determined by potentiometric titration and are similar with the related values of DTPA and Gd-DTPA respectively. The results obtained show that the basicity of the ligand and the stability constant of its Gd(Ⅲ) chelate are not obviously altered after introduction of a linear chain tetradecyl group at the terminal acetic acid residue of DTPA.     

用IR和负离子FAB—MS测定EDTA,DTPA及其碱金属盐类结构

用ＩＲ和负离子ＦＡＢ－ＭＳ测定不同ｐＨ值下ＥＤＴＡ，ＤＴＰＡ，及其碱金属盐类，能直接给出它们的结构及其分子量，对于其碱金属盐类的混合物，不经分离，可以直接测定，能同时得到混合物中各组分的相对分子质量。     

Fluorescence Sensitization of Aqueous Terbium and Europium Ions Without Aromatic Donors or Synergistic Agents

Abstract

EDTA and DTPA complexes of terbium and europium are excited at wavelengths below 250 nm. producing the typical lanthanide emission through energy transfer from the complex to the coordinated metal. This allows determination of these rare earth ions in water without solvent extraction, the use of synergistic agents, or aromatic sensitizers. Terbium-EDTA has the most efficient energy transfer, 31%, giving a 165-fold emission enhancement and a limit of detection of 6 × 10^?7 M. Calibration curves are linear over a concentration range spanning three orders of magnitude. The characteristic lanthanide ion emission is obtained in all cases, but the excitation of the complexes is pH dependent, showing intensity increases up to pH 12. Mild interference by alkali and alkaline earth metals was overcome by increasing the ligand concentration, but transition metal interference was more severe. Only minor enhancement was observed at higher ligand/metal ratios.     

Complexation of gadolinium(III) ions on top of nanometre-sized magnetoliposomes

The complex of diethylenetriaminepentaacetate (DTPA) with the paramagnetic gadolinium ion [Gd(III)] is a well-known blood pool contrast agent for magnetic resonance imaging (MRI). To obtain MRI pictures from other anatomical structures, for instance from tissues containing cells with phagocytic activity, larger colloidal complexes have to be constructed. Therefore, in view of modifying the physiological behaviour, the DTPA chelate was first hydrophobized by covalently linking it to phosphatidylethanolamine (PE), and the resulting conjugate was then incorporated into nanometre-sized, sonicated phospholipid vesicles. Qualitative information on the affinity of the PE–DTPA derivative for Gd(III) ions was derived from competition experiments using the dye Arsenazo. Furthermore, it was found that only the membranotropic adducts residing in the outer shell of the vesicle bilayer are accessible to the lanthanide ion. The vesicular particulate was also used as a vehicle to transport PE–DTPA into the coating of so-called magnetoliposomes which consist of nanometre-sized iron oxide cores onto which a phospholipid bilayer is strongly chemisorbed. After loading the resulting structures with Gd(III), this new type of magnetoliposome may offer unique potentialities as a novel bi-label MRI contrast medium.     

Synthesis of bifunctional chelating agents based on mono and diphosphonic derivatives of diethylenetriaminepentaacetic acid

Bifunctional chelating agents (BFCAs) are small molecules containing a chelating unit, able to strongly coordinate a metal ion, and a reactive functional group, devised to form a stable covalent bond with another molecule. BFCAs are widely employed since their conjugation to a suitable biomolecule (e.g., a peptide or an antibody) allows the synthesis of diagnostic or therapeutic agents that specifically target diseased tissue with metals or radiometals. For this reason, BFCAs find application in diagnostic imaging, molecular imaging, and radiotherapy of cancer. The synthesis of new BFCAs based on a diethylenetriaminepentaacetic acid (DTPA) structure in which one or two carboxylic groups are replaced with phosphonic units is described. The phosphonic group, aside from being a classical isostere of the carboxylic acid in coordination chemistry, allows to modulate the physico-chemical properties of the ligands and of the corresponding complexes.     

Developing a robust LC–MS/MS method to quantify Zn‐DTPA,a zinc chelate in human plasma and urine

Quantitation of Zn‐DTPA (zinc diethylenetriamene pentaacetate, a metal chelate) in complex biological matrix is extremely challenging on account of its special physiochemical properties. This study aimed to develop a robust and specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for determination of Zn‐DTPA in human plasma and urine. The purified samples were separated on Proteonavi (250 × 4.6 mm, 5 μm; Shiseido, Ginza, Tokyo, Japan) and a C₁₈ guard column. The mobile phase consisted of methanol–2 mm ammonium formate (pH 6.3)–ammonia solution (50:50:0.015, v/v/v), flow rate 0.45 mL/min. The linear concentration ranges of the calibration curves for Zn‐DTPA were 1–100 μg/mL in plasma and 10–2000 μg/mL in urine. The intra‐ and inter‐day precisions for quality control (QC) samples were from 1.8 to 14.6% for Zn‐DTPA and the accuracies for QC samples were from −4.8 to 8.2%. This method was fully validated and successfully applied to the quantitation of Zn‐DTPA in plasma and urine samples of a healthy male volunteer after intravenous infusion administration of Zn‐DTPA. The result showed that the concentration of Zn‐DTPA in urine was about 20 times that in plasma, and Zn‐DTPA was completely (94.7%) excreted through urine in human.     

Spectrometric and theoretical investigation of the structures of Cu and Pb/DTPA complexes

Spectrometric and theoretical tools have been employed in this study in order to elucidate the structures of DTPA (diethylenetriaminepentaacetic acid) complexed to copper and lead. Mass spectrometry allowed determining the 1:1 stoichiometry of metal:ligand, while infrared spectroscopy demonstrated that both N and O are sites for complexation. ¹³C NMR analysis showed the existence of free and complexed carboxyl groups, due to a straight singlet at 180.7 ppm (free carboxylic ¹³C) and to a broad signal at 179.3 ppm (complexed carboxylic ¹³C, ² J _Pb…O=C). A distorted NMR signal were observed for the Cu–DTPA carboxyl group, due to the Cu²⁺ paramagnetism. Based on the spectrometric evidences for the metal–DTPA structures, DFT optimizations were carried out and an octahedral-like arrangement for the Cu complex and a “shell-like” arrangement for the Pb complex, both hexa-coordinated, were then proposed for the structures of the titled compounds.