Extraction chromatography using chelating agents

The extraction-chromatographic behaviour of copper, indium and thorium was investigated on a column with N-benzoyl-N-phenylhydroxylamine in chloroform. From the results the values of the extraction constanst of the metal chelates were calculated and found to be in good agreement with the published values. It is possible to calculate the optimum conditions for the separation of the different metals from known extraction constants. The separation of⁶⁵Zn−⁶⁴Cu;⁶⁰Co−⁵⁹Fe;⁶⁰Co−⁶⁴Cu−⁵⁹Fe;²³⁸U−²³⁴Th(UX₁) and²³²Th−²³³Pa in this system is reported. The described procedures were used for the preparation of carrier-free²³⁴Th(UX₁) from uranyl nitrate and²³³Pa from irradiated thorium. Part II: J. Radional. Chem., 7 (1971) 41.     

Extraction chromatography using chelating agents

The extraction-chromatographic behaviour of zinc on a column with dithizone as chelating agent has been investigated in the absence and presence of oxalic acid as masking agent. From the results the extraction constant and the stability constants of zinc oxalate complexes have been determined. These values are in good agreement with the published data so that it seems possible to predict the extraction-chromatographic separation of various metals from known extraction and stability constants.     

Extraction chromatography using chelating agents

The separation of Zn?Cd, Ag?Hg, Cd?Ag and Pb?Bi?Po by extraction chromatography in the system dithizone-carbon tetrachloride is reported. It is shown that it is possible to calculate optimum conditions for the separation of the metals from the extraction constants of the metal chelates and the stability constants of the metal complexes with masking agents.     

High-speed recovery of antimony using chelating porous hollow-fiber membrane

A porous hollow-fiber membrane containing an iminodiethanol (IDE) group as the chelate-forming group was applied to the recovery of antimony in the permeation mode. An antimony solution was forced to permeate through the pores of the chelating porous hollow-fiber membrane, driven by a transmembrane pressure. The membrane with a thickness of 0.7 mm and a porosity of 70% had an iminodiethanol group of 1.6 mol/kg of the membrane and a water flux of 0.95 m/h at 0.1 MPa and 298 K. The breakthrough curves of antimony overlapped irrespective of the permeation rate of the antimony solution ranging from 2 to 20 ml/min, i.e. the residence time across the membrane thickness ranging from 3.4 to 0.34 s, because of negligible diffusional mass-transfer resistance of the ionic species of antimony to the iminodiethanol group. At antimony concentrations below 10 mg/l (pH 4.0), a linear adsorption isotherm was obtained. The adsorbed antimony was quantitatively eluted by permeation of 2 M hydrochloric acid through the pores of the membrane.     

Development of poly(vinyl chloride)/montmorillonite nanocomposites using chelating agents

Different chelating agents such as poly(ethylene glycol), propylene glycol monooctadecanoate and palm oil were used for modification of the surface-treated montmorillonite (MMT). The work also included the development of a technique for mixing chelating agents with MMTs using different methods and different proportions of MMT/chelating agent/ethanol. Evaluation of the result of mixing was performed by thermogravimetric analysis, X-ray diffraction and high-resolution scanning electron microscopy (HR-SEM). The results showed that the chelating agents used were intercalated in MMT, increasing the interlayer spacing. The OMMT was used in the manufacture of composites with rigid PVC using a microcompounder. The master batch concept turned out to be promising in terms of dispersion and delamination of clay, as observed in HR-SEM photographs. However, despite good dispersion and exfoliation of MMT, poor compatibility between clay platelets and PVC matrix remains to be solved to enable full exploitation of its engineering potential. Despite this drawback, good thermal stability and mechanical properties have already been achieved.     

Dithiocarbamates derived from aspartic and glutamic acids as chelating agents

Dithiocarbamates (dtc's) derived from aspartic (asp) and glutamic (glu) acids have been synthesized and characterized. Their Ba salts are of the general formula Ba₃(dtc–aa)₂, where aa = amino acid. The dithiocarbamates react with Ni^II salts to yield square-planar complexes, [Ni(dtc–aa)₂]. Complexes with Pb^II and Cd^II, with formula [M₃(dtc–aa)₂], are insoluble in water, and for Cd^II a second compound can be isolated in an acidic medium for the glutamic acid derivative, with formula [Cd(dtc–glu)]. Conductivity measurements indicate an appreciable affinity of the dithiocarbamates for these metal ions, with an almost quantitative scavenging ability.     

Efficient and tunable synthesis of new polydentate bifunctional chelating agents using click chemistry

Two novel bifunctional chelating agents, which are bistriazole-based polyaminocarboxylic acids, have been designed and synthesised in high yields. An elegant synthetic approach using the Cu-catalysed azide-alkyne cycloaddition has been developed. This convenient route could be employed for the synthesis of a variety of polydentate bifunctional chelators.     

An alternative separation procedure for 90Sr age dating using DGA Resin

Journal of Radioanalytical and Nuclear Chemistry - The likelihood of an attack by a terrorist organization using a radiological dispersal device (RDD) is much higher than that of an attack with an...     

Iron chelating agents for the treatment of iron overload

The importance of iron chelators in medicine has significantly increased in recent years. Iron is essential for life but it is also potentially more toxic than other trace elements. This is because we lack effective means to protect human cells against iron overload and because of the role of iron in the generation of free radicals. In order to protect patients from the consequences of iron toxicity, iron chelating agents have been introduced in clinical practice. Unfortunately, the ideal chelator for treating iron overload in humans has not been identified yet. In this paper we examine a few characteristics of iron chelators, with some emphasis on the effects of redox cycling, on absorption mechanisms and on some properties of the pFe. A brief summary is then made of the chelators recently proposed or in development for the treatment of iron overload.     

New chelating agents for colorimetric determination of calcium

Two new calcium chromoionophores2 and3 are described and their potential application to colorimetric determination of calcium is assessed. Chromogenic compound2 bears two acetic acid chelating groups and a 4-(4-nitrophenyl)azophenol chromophore. Its complexation of Ca²⁺ at pH 9.0 is accompanied by a 109-nm bathochromic shift and increase in the absorptivity. Triaryl chromoionophore3 bears two phosphonic acid chelating groups and the same azophenol chromophore. Compound3 exhibits a 107-nm bathochromic shift of the absorption maximum, an increase in the absorptivity upon complexation with Ca²⁺, and good selectivity for Ca²⁺ over Mg²⁺ at pH 7.0. Both chromoionophores exhibit linear responses from 0 to 4×10^–3 M Ca²⁺.     

Gas chromatographic separation of the stereoisomers of organophosphorus chemical warfare agents using cyclodextrin capillary columns

The synthesis of the organophosphorus nerve agents sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) produces a mixture of two stereoisomers except for soman where four stereoisomers are produced. Significant differences exist in the reported toxicity and AChE inhibition rates of the various stereoisomers. This makes the ability to distinguish between the different stereoisomers desirable. Five different derivatized cyclodextrin stationary phases developed for gas chromatography were tested for their ability to resolve the nerve agent stereoisomers using a gas chromatograph interfaced to an atomic emission detector. Of the five columns that we examined, only the 2,6-di-O-pentyl-3-O-trifluoroacetyl or 2,6-di-O-pentyl-3-O-butyryl γ-cyclodextrins were able to successfully resolve all four soman stereoisomers. The elution order for each column was determined using solutions of isolated soman stereoisomers. Enantiomers of sarin, tabun, and GF were resolved with varying degrees of success on the different cyclodextrin stationary phases. Only the butyryl γ-cyclodextrin was able to separate the enantiomers of all four of the nerve agents examined in this study. The capacity (k) and selectivity (α) factors were determined for each of the chemical warfare agents successfully separated. The TNO Prins Maurits Laboratory in the Netherlands has previously developed several different chromatographic methods to resolve the stereoisomers of soman, sarin, and tabun. The advantage of the method described here is that commercially available cyclodextrin gas chromatography columns were used to resolve the stereoisomers, thereby facilitating rapid and routine analysis of organophosphorus nerve agents.     

HPLC analysis of metal chelating agents in micronutrients

The separation and quantitative determination of organic chelating agents such as DTPA, EDDHA, EDDHMA, EDTA and HEDTA as their copper chelates using HPLC and UV detection is described. Analysis is performed on a Spherogel^TM TSK column. The eluent consists of methanol/water (50: 50, v/v) and 0.25 mmol/L Cu(NO₃)₂. The pH value, the composition of the eluent, the temperature, the sample concentration, the flow rate of the eluent and the influence of the detection wavelength were optimized. The linearity of the UV detector was in the range of 0.5 mmol/L to 2.5 mmol/L.     

Hydroxytriazenes--a review of a new class of chelating agents

A review of the applications of hydroxytriazenes as chelating agents in analytical chemistry.     

Comparison of two chelating agents immobilized on controlled-pore glass for the preconcentrationof aluminium from aqueous solutions

Aluminium at low μg cm^?3 levels can be preconcentrated on columns of 8-quinolinol or EDTA immobilized on controlled-pore glass. Distribution coefficients are ca. 45 and 370 cm² g^t-1, respectively, and recoveries of aluminium are >80% at pH >4.6 and pH >4.0, respectively. The eluted aliminium is determined by atomic absorption spectrometry in a nitrous oxide/acetylene flame.     

Synthesis of new semi-rigid chelating agents for samarium-153

This study describes a simple, efficient synthesis pathway from trans-1,2-diaminocyclohexane that provides access to a new class of semi-rigid polyamine, polycarboxylic, and polyphosphonic ligands. The key steps in synthesis were the functionalisation (with an appropriate branching group) of a bisphosphonate diaminocyclohexane derivative and the introduction of methanephosphonic functions by a rarely used method.     

Synthesis of some imidazole- and pyrazole- derived chelating agents

Procedures involving condensation of o-phenylenediamines with carboxylic acids, and reaction of bifunctional alkyl halides with bifunctional nucleophiles are described. Syntheses are reported of 2,6-bis-(2-benzimidazyl)-pyridine, 1,3-bis(2-benzimidazyl)-2-thiapropane, 1,7-bis(2-benzimidazyl)-2,6-dithiaheptane, 2-hydroxymethyl-5,6-dimethylbenzimidazole, 2-chloromethyl-5,6-dimethylbenzimidazole hydrochloride, 1,7-bis(5,6-dimethyl-2-benzimidazyl)-2,6-dithiaheptane, 3,6-bis(1-pyrazolyl)pyridazine, 2-(2-hydroxy-3-methyl–phenyl)benzimidazole, 2-(2-hydroxyphenyl)benzimidazole, 5-(2-hydroxphenyl)-3-methyl-1-phenylpyrazole, 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole, 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole, and 1,3-bis((5-methylpyridyl)imino)isoindoline.     

几种新的4-酰基吡唑酮类螯合剂的合成

Eight new 1-phenyl-3-methyl-4-acyl-pyrazolones (1a-f, 2a, b) have been synthesized in good yield by reacting the corresponding acid halide with 1-phenyl-3-methyl-pyrazolone in dioxane in the presence of suspended Ca(OH)2 or Ba(OH)2, the products were identified by elemental analyses, IR, UV and 1H NMR spectra. Preliminary experiments indicate that all of their extraction efficiency for (UO2)2+ in chloroform-water are better than that of PMBP. The relative efficiency is found to be of the following order: 1b, 1d, 1f>1a, 1e>1c, 2a>2b>PMBP.     

Chemi-ionization reactions of Ba,Sr, Ca with OH

Associative ionization has been observed in the ractions of Ba, Sr, Ca (M) with OH, M + OH = MOH⁺ + e^?, and relative rates have been measured under effusive thermal cross molecular beam conditions. The rates are in the ratio 3 × 10³, 3 × 10¹ to 1 for Ba, Sr, relative to Ca.