Structural determination of Zn and Cd-DTPA complexes: MS, infrared, (13)C NMR and theoretical investigation

The joint application of MS, infrared and (13)C NMR techniques for the determination of metal-DTPA structures (metal=Zn and Cd; DTPA=diethylenetriaminepentacetic acid) is reported. Mass spectrometry allowed determining the 1:1 stoichiometry of the complexes, while infrared analysis suggested that both nitrogen and carboxyl groups are sites for complexation. The (13)C NMR spectrum for the cadmium-containing complex evidenced the existence of free and complexed carboxyl groups, due to a straight singlet at 179.0 ppm (free carboxylic (13)C) and to two broad singlets or a broad doublet at 178.3 ppm (complexed carboxylic (13)C, (2)J(Cd-C(=O))=45.2 Hz). A similar interpretation might be given for the zinc derivative and, with the aid of DFT calculations, structures for both complexes were then proposed.     

Analysis of EDTA and DTPA

In this paper, analytical techniques for the determination of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) are reviewed. These compounds, especially EDTA, are used as metal chelating agents in several industries. As they are likely to be poorly degraded in waste water treatment plants, significant amounts of EDTA and DTPA are released into natural waters. The overview consists of comparing chromatographic, electrochemical, spectrophotometric, titrimetric and atomic absorption methods and their applicability to the determination of EDTA and DTPA in different matrices.     

Isotachophoretic determination of stability constants of Ho and Y complexes with diethylenetriaminepentaacetic acid and 1,4,7,10-tetraazadodecane-N,N',N'',N'''-tetraacetic acid

The method of capillary isotachophoresis with conductivity detection was applied for the determination of the physico-chemical characteristics (conditional stability constants log beta') of holmium and yttrium complexes with DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazadodecane-N,N',N',N'-tetraacetic acid). The log beta' determination is based on the linear relation between the stability constants of lanthanide-DTPA (lanthanide-DOTA) complexes and the reduction of the zone of the complex owing to the bleeding phenomena (liberating free metal ion). The stability constants calculated using this relationship are comparable with the literary data obtained by other methods for both holmium (log beta'(Ho-DTPA)=21.9, log beta'(Ho-DOTA)=24.5) and yttrium complexes (log beta'(Y-DTPA)=21.2, log beta'(Y-DOTA)=24.4). Capillary isotachophoresis was applied for the determination of the optimum composition of the reaction mixture (metal:ligand ratio) as well.     

Speciation of chromium in the waste water from a tannery

Due to the different toxicity of chromium (VI) and chromium (III) and the different toxicity of free hydrated metal ions versus stable complexes of the ions, the determination of the physicochemical form of the chromium is necessary in addition to the total metal content. In this investigation a strategy of analysis has been developed which provides information about the physicochemical form, toxicity and ecochemical behaviour of the chromium in the waste water. The strategy was used for the analysis of two waste water samples. The investigations were not able to give exact quantitative results for the different species initially present because each method shifted the equilibrium state. It was shown that the more toxic chromium (VI) species was unstable in both the waste water samples investigated. Although the two waste waters came from very different sources, most of the chromium (III) in both waste waters after centrifugation were not free ionic species but were associated with macromolecular particles (complexed or colloidal). 36% and 46% of the total chromium of the two samples was bound in a very stable complex; 25% and 15% was bound as colloids. Only a small part of the chromium was ionic (and hence particularly toxic). Despite the stable binding, most of the chromium could be coprecipitated with Fe(OH)₃ or Al(OH)₃ in laboratory experiments and would probably be mineralised in natural water.     

Confirmation of iron complex formation using electrospray ionization mass spectrometry (ESI-MS) and sample stacking for analysis of iron polycarboxylate speciation by capillary electrophoresis

The use of capillary electrophoresis (CE) and UV detection for the determination of metal speciation is based on the standards via matching migration time. Consequently, it requires that the metal species are stable during electrophoresis. Migration time of the metal species is dependent on the electrolyte composition. However, the stability for such metal complexes is also dependent on electrolyte composition and electrolyte-specific stability is not always well known. In this paper, the stability of iron (Fe) polycarboxylate complex formation was determined using electrospray ionization mass spectrometry (ESI-MS). Mass spectra indicates that Fe[DTPA]²⁻, Fe[EDTA]⁻, Fe[HEDTA] and Fe[NTA] were present in solution but the mass spectrum for Fe[NTA] was found to be weak. An electrolyte containing 25 mM NaH₂PO₄ and 0.25 mM tetradecyltrimethylammonium bromide (TTAB) at pH 6.0 was used to successfully separate Fe[DTPA]²⁻, Fe[EDTA]¹⁻ and Fe[HEDTA]. The instability of Fe[NTA] meant it was not observed due to its instability during electrophoresis. To improve UV detection limits sample stacking techniques, such as large volume sample stacking (LVSS) without polarity switching and filed-amplified sample injection (FASI), were investigated. The results show that less than 0.01 μM detection limits for the Fe complexes were obtained using FASI. The calibration plots were linear from 0.05-3.0 with good reproducibility (peak area: 6.5-8.1%) when a water plug was used. Finally, the proposed method was demonstrated for the determination of trace Fe complexes in river waters.     

Insight into the Dynamics of Lanthanide-DTPA Complexes As Revealed by Oxygen-17 NMR

DTPA chelates of various diamagnetic and paramagnetic lanthanide(III) metal ions, as well as the chemically similar DTPA chelate of Y(3+), were studied in aqueous solution by variable temperature (17)O NMR with the aim of characterizing their internal dynamics. As a consequence of poor chemical shift dispersion and fast quadrupole relaxation, no dynamic exchange process could be detected for the diamagnetic complexes nor for the Sm-DTPA complex. In contrast, the spectra recorded for the Eu-DTPA complex show chemical exchange due to the well-known racemization process and, at high temperature, feature signal broadening that reveals a fluxional process involving the interchange of the coordinated and noncoordinated oxygen atoms of the carboxylate groups. The spectra recorded for the Pr-DTPA complex feature coalescence events due to such a fluxional process, which is ascribable to the rotation of the carboxylate groups. The activation free energy barriers determined experimentally are remarkably lower than the calculated activation barriers recently reported for the rotation of the carboxylate groups of various Ln-DOTA complexes. Furthermore, the smallest activation free energy measured for the Pr-DTPA complex, about 45 kJ mol(-1), is significantly lower than the activation free energy characterizing the racemization process. The fluxional behavior of the carboxylate groups is, however, not expected to significantly affect the residence time of the water molecule coordinated to the metal ion.     

Complexation reactions of pyridinols

Complexation of iron(III) with several pyridinols has been studied and used in selective detection and determination (spectrophotometric and chelatometric) of the metal. Iron(III)-pyridinol complexes are also used as indicators in acid-base titrations. A thiol group vicinal to a phenol group in a pyridine molecule provides a reagent that is a suitable ligand for palladium(II) determination. Stability constants of bivalent metal complexes with pyridinols have been determined potentiometrically.     

Rapid and sensitive determination of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid in water samples by ion-pair reversed-phase liquid chromatography--electrospray tandem mass spectrometry

A new method is presented for the quantitative determination of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) from aqueous samples without an enrichment step. It consist of the formation of the Fe(III) complexes of EDTA and DTPA, liquid-chromatography with a volatile ion-pairing agent and determination by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Limits of quantification (LOQ) of 1.0 and 0.6 microgL(-1) for EDTA and DTPA were obtained, allowing the direct injection of most aqueous environmental samples without any preceding enrichment. With a more recent mass spectrometer, the LOQ could be further decreased by almost one order of magnitude. Parallel analysis of real samples by a standardized method employing enrichment, derivatization and GC-MS analysis yielded comparable results. The method was applied to the determination of both complexing agents in several wastewater, surface water and drinking water samples, showing that EDTA is an omnipresent contaminant in partially closed water cycles.     

Isotachophoretic determination of stability constants of Ho and Y complexes with diethylenetriaminepentaacetic acid and 1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid

The method of capillary isotachophoresis with conductivity detection was applied for the determination of the physico-chemical characteristics (conditional stability constants log β′) of holmium and yttrium complexes with DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazadodecane-N,N′,N″,N-tetraacetic acid). The log β′ determination is based on the linear relation between the stability constants of lanthanide–DTPA (lanthanide–DOTA) complexes and the reduction of the zone of the complex owing to the bleeding phenomena (liberating free metal ion). The stability constants calculated using this relationship are comparable with the literary data obtained by other methods for both holmium (log β′_Ho–DTPA=21.9, log β′_Ho–DOTA=24.5) and yttrium complexes (log β′_Y–DTPA=21.2, log β′_Y–DOTA=24.4). Capillary isotachophoresis was applied for the determination of the optimum composition of the reaction mixture (metal:ligand ratio) as well.     

Assessment of single extractions for the determination of mobile forms of metals in highly polluted soils and sediments--analytical and thermodynamic approaches

Highly polluted forest/tilled soils and stream sediments from a mining and smelting area were subjected to single-extraction procedures to determine the extractable contents of Cd, Cu, Pb, and Zn. The results obtained from four widely used operationally defined single extraction tests were compared: deionised water, 0.01 mol L⁻¹ CaCl₂, 1 mol L⁻¹ NH₄NO₃ and 0.005 mol L⁻¹ DTPA. The analytical data were coupled with measurement of the pH and Eh in extracts, mineralogical investigations and thermodynamic modelling using the PHREEQC-2 code. The changes in the pH of the equilibrated suspensions significantly influenced the metal extractabilities, with higher values in the lower pH regions. Although the DTPA procedure generally extracted the highest amounts of metals, it was found to be unsuitable for highly organic acidic forest soils, where anionic metal-DTPA complexes are assumed to be re-adsorbed on the positively charged surfaces of soil organic matter and oxides. The NH₄NO₃ extraction was also unsuitable due to the high ionic strength (1 mol L⁻¹), limiting the use of the thermodynamic speciation model and the formation of the Cu(NH₃)²⁺ complex, leading to acidification of the suspension. 0.01 mol L⁻¹ CaCl₂ can be proposed as the most appropriate extraction medium, suitable for speciation modelling and analytical determinations using ICP-techniques and having an ionic strength similar to that of the soil solution. The metals are present in free ionic forms or chlorocomplexes in the CaCl₂ extracts, preventing their re-adsorption on the positively charged surfaces of soil solids (organic matter, Fe- and Mn-oxides) in acidic and circum-neutral conditions.     

Determination of 1,4-Dichlorobenzene in Environmental Matrices

1,4-Dichlorobenzene is a frequently used lavatory deodorant although it has strong endocrine disrupting and potential carcinogenic effects. A large amount (approximately 15,000 tonnes annually worldwide) of this compound is released into the environment. This paper deals with the determination of 1,4-dichlorobenzene in a variety of environmental matrices. Various extraction and concentration methods such as charcoal absorbtion tubes and headspace sampling were applied. Sensitive and selective ion monitoring GC-MS measurements were used for determination. Significant concentrations of the compound have been identified in lavatory air, waste water, waste water sludge and human breast milk.

     

Gd(DTPA-BIN)与人血清白蛋白作用的核磁共振研究

造影剂通常为Ｇｄ３＋、Ｍｎ２＋或Ｆｅ３＋的稳定化合物．它们能改变体内水分子氢核的弛豫速率,从而提高正常与病变组织的磁共振成像（ＭａｇｎｅｔｉｃＲｅｓｏｎａｎｃｅＩｍａｇｉｎｇ,ＭＲＩ）对比度或显示体内器官的功能状态．因此,开发新优ＭＲＩ造影剂具有重要...     

Spectroscopic and Computational Characterization of Diethylenetriaminepentaacetic Acid/Transplutonium Chelates: Evidencing Heterogeneity in the Heavy Actinide(III) Series

The chemistry of trivalent transplutonium ions (Am³⁺, Cm³⁺, Bk³⁺, Cf³⁺, Es³⁺…) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. Herein, we present the first extended X‐ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal–oxygen nearest‐neighbor bond lengths in the case of Cf³⁺. Corroborating those results, density functional theory calculations, extended to Es³⁺, suggest that the shorter Cf?O and Es?O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [M^IIIDTPA(H₂O)]^2? (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.     

Synthesis of Two Derivatives of 3,6,9‐tri(carboxymethyl)‐3,6,9‐triazaundecanedioic Acid and the Stabilities of Their Complexes with Ca2+, Cu2+, Zn2+, Dy3+ and Gd3+

Two N‐2‐hydroxy‐1‐phenylethyl and N‐2‐hydroxy‐2‐phenylethyl derivatives of DTPA (3,6,9‐tri(carboxymethyl)‐3,6,9‐triazaundecanedioic acid), DTPA‐H1P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐1‐phenylethyl‐3,6,9‐triazaundecanedioic acid, and DTPA‐H2P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐2‐phenylethyl‐3,6,9‐triazaundecanedioic acid were synthesized. Their protonation constants were determined by Potentiometric titration in 0.10 M Me₄NNO₃ and by NMR pH titration at 25.0 ± 0.1°C. The formations of lanthanide(III), copper(II), zinc(II) and calcium(II) complexes were investigated quantitatively by potentiometry. The stability constant for Gd(III) complex is larger than those for Ca(II), Zn(II) and Cu(II) complexes with these two ligands. The selectivity constants and modified selectivity constants of the DTPA‐H1P and DTPA‐H2P for Gd(III) over endogenously available metal ions were calculated. Comparing pM values at physiological pH 7.4 assesses effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media. The observed water proton relaxivity values of [Gd(DTPA‐H1P)]^? and [Gd(DTPA‐H2P)]^? became constant with respect to pH changes over the range of 4‐10. ¹⁷O NMR shifts showed that the [Dy(DTPA‐H1P)]^? and [Dy(DTPA‐H2P)]^? complexes at pH 6.30 had 1.91 and 2.28 inner‐sphere water molecules, respectively. Water proton spin‐lattice relaxation rates of [Gd(DTPA‐H1P)]^? and [Gd(DTPA‐H2P)]^? complexes were also consistent with the inner‐sphere Gd(III) coordination.     

Synthesis and Evaluation of Aromatic DTPA-bis(amide) Gadolinium Complexes as Magnetic Resonance Imaging Contrast Agents

ＳｙｎｔｈｅｓｉｓａｎｄＥｖａｌｕａｔｉｏｎｏｆＡｒｏｍａｔｉｃＤＴＰＡ┐ｂｉｓ（ａｍｉｄｅ）ＧａｄｏｌｉｎｉｕｍＣｏｍｐｌｅｘｅｓａｓＭａｇｎｅｔｉｃＲｅｓｏｎａｎｃｅＩｍａｇｉｎｇＣｏｎｔｒａｓｔＡｇｅｎｔｓＺＨＵＯＲｅｎ－Ｘｉ＊＊，ＷＥＮＪｉｅ...     

用DL-半胱氨酸盐作螯合滴定释放剂的研究和应用

提出以DL-半胱氨酸盐（DL-Cysteine）作释放剂，选择性螯合滴定法测定铜或锡、汞和铊．方法是基于先用EDTA螯合铜（Ⅱ）或锡（Ⅳ）、汞（Ⅱ）、铊（Ⅲ）和其它金属离子，然后用DL-Cysteine解蔽．其它金属离子均不干扰。在测定条件下．试剂（DL－Cysteine）不与大量其它金属-ED-TA配合物起反应。此法已经用于测定各种合金和矿样中的铜或锡、汞和铊，结果令人满意。     

Complexation of N-bis[2-(1,2-dicarboxyethoxy)ethyl]aspartic acid with Cd(II), Hg(II) and Pb(II) ions in aqueous solution

The persistence of widely used chelating agents EDTA and DTPA in nature has been of concern and there is a need for ligands to replace them. In a search for environmentally friendly metal chelating ligands for industrial applications, complex formation equilibria of N-bis[2-(1,2-dicarboxyethoxy)ethyl]aspartic acid (BCA6) with Cd(II), Hg(II) and Pb(II) in aqueous 0.1 M NaNO₃ solution were studied at 25°C by potentiometric titration. Complexation was modeled and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metal ions, stable ML^4? complexes dominated the complex formation. The stabilities of Cd(II), Hg(II) and Pb(II) chelates of BCA6 are remarkably lower than those of EDTA and DTPA. Environmental advantages of the use of BCA6 instead of EDTA and DTPA are better biodegradability and lower nitrogen content with a possibility to save chemicals and process steps in pulp bleaching.     

Complexes of diethylenetriaminepentaacetic acid as contrast agents in NMR imaging. Computer simulation of equilibria in human blood plasma

In magnetic resonance imaging (MRI), the degree of contrast can be improved by using suitable contrast agents. The diethylenetriaminepentaacetic acid (DTPA) complexes of paramagnetic ions have been proposed for this purpose. This paper deals with extensive simulations of the distribution of species in blood plasma when solutions of manganese(II), copper(II), iron(III) and gadolinium(III) ions (as their soluble salts and as DTPA complexes) are injected. The various interaction equilibria, for which formation constants are known, are considered in order to assess toxic side-effects associated with their use in MRI. The data obtained support from the thermodynamic point of view, the use of GdDTPA, and suggest that the administration of a slight excess of ligand would guarantee complete coordination of the toxic gadolinium ion, and only minor interaction with the metal ions naturally present in blood plasma.     

Simple and Highly Selective Catalytic Adsorptive Voltammetric Method for Cr(VI) Determination

A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of traces of Cr(VI) in the presence of a large excess of Cr(III) in environmental water samples is reported. To obtain a low detection limit the voltammetric procedure of chromium determination in the presence of DTPA and nitrate was exploited. For elimination of interference of Cr(III) ethylenediaminedisuccinic acid was used as a masking agent. At optimized conditions the calibration graph is linear from 2×10^?10 to 2×10^?8 mol L^?1 for accumulation time of 30 s. The validation of the procedure was performed by comparison of the results of analysis of river water samples with those obtained using other accepted voltammetric procedure.     

Use of fluorescence spectroscopy and voltammetry for the analysis of metal-organic matter interactions in the New Caledonia lagoon

Fluorescence, polarographic and potentiometric analysis of sea water from the New Caledonia lagoon (located south of Noumea) allowed the determination of the specific properties of the dissolved and particulate phases of organic matter (OM)-metal complexes according to various regions of the lagoon. In particular, OM complexes with Ni, Zn, Pb, Cu, Cd were chosen in this study due to the sensitivity of these complexes to affect biocenosis of the nearby enclosed coral reef as well as their availability to enter the coast from erosion (terrigenous OM) or human activities from nickel extraction or pollution from waste sites (anthopogenic OM) that exist throughout New Caledonia. Combined with geochemical modelling, the OM-metal complexes analysis allowed the determination of their conditional stability constants which in turn helped in predicting the fate of the metal pollution in the lagoon. For the first time, fluorescence, polarographic and potentiometric techniques combined with geochemical models that employed discrete pKa distribution on OM enabled the determination of the origin of the OM, as either natural or anthopogenic.