HEDTA Research Articles

Supramolecular Branching and Crosslinking of Terpyridine‐Modified Copolymers: Complexation and Decomplexation Studies in Diluted Solution

AbstractA series of poly(methyl methacrylate) copolymers with terpyridine units in the side chains was obtained by free radical polymerization. The free terpyridine units were complexed by iron(II) and zinc(II) ions, and the complexation behavior was studied in detail, utilizing UV‐vis and viscosity titration experiments. Complexation of the polymer chains could be observed, which resulted in characteristic UV‐vis absorption bands and an increase in the solution viscosity. Addition of a strong competitive ligand (hydroxyethyl ethylenediaminetriacetic acid, HEEDTA) resulted in an efficient decomplexation.UV‐vis spectra and photos of uncomplexed copolymer 2b before and after complexation with iron(II) ions (in chloroform) and after decomplexation with HEEDTA.magnified imageUV‐vis spectra and photos of uncomplexed copolymer 2b before and after complexation with iron(II) ions (in chloroform) and after decomplexation with HEEDTA.

Final report on the safety assessment of EDTA, calcium disodium EDTA, diammonium EDTA, dipotassium EDTA, disodium EDTA, TEA-EDTA, tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, HEDTA, and trisodium HEDTA.

EDTA (ethylenediamine tetraacetic acid) and its salts are substituted diamines. HEDTA (hydroxyethyl ethylenediamine triacetic acid) and its trisodium salt are substituted amines. These ingredients function as chelating agents in cosmetic formulations. The typical concentration of use of EDTA is less than 2%, with the other salts in current use at even lower concentrations. The lowest dose reported to cause a toxic effect in animals was 750 mg/kg/day. These chelating agents are cytotoxic and weakly genotoxic, but not carcinogenic. Oral exposures to EDTA produced adverse reproductive and developmental effects in animals. Clinical tests reported no absorption of an EDTA salt through the skin. These ingredients are likely, however, to affect the passage of other chemicals into the skin because they will chelate calcium. Exposure to EDTA in most cosmetic formulations, therefore, would produce systemic exposure levels well below those seen to be toxic in oral dosing studies. Exposure to EDTA in cosmetic formulations that may be inhaled, however, was a concern. An exposure assessment done using conservative assumptions predicted that the maximum EDTA dose via inhalation of an aerosolized cosmetic formulation is below that shown to produce reproductive or developmental toxicity. Because of the potential to increase the penetration of other chemicals, formulators should continue to be aware of this when combining these ingredients with ingredients that previously have been determined to be safe, primarily because they were not significantly absorbed. Based on the available data, the Cosmetic Ingredient Review Expert Panel found that these ingredients are safe as used in cosmetic formulations.

Effect of Ligands on the Redox Reactions of Silver Metal Clusters

The reduction of silver ions and their subsequent agglomeration was studied in aqueous solutions in the presence of N-(hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), iminodiacetic acid, 5-aminotetrazole, benzotriazole, and 2-mercaptobenzimidazole as ligands. The presence of ligands in the solution affects the early processes via the complexation of Ag+ ions with the carboxyl and amino moieties of the ligands. Also, it reduces somewhat the rate of reduction by hydrated electrons. The transient absorption spectra of Ag0, Ag2+ and Ag20 and their successive rate constants have been determined. The red shift in the band of silver atoms was found to be more pronounced when the ligand interaction is stronger. This was correlated with the ligand-induced redox properties of the silver couple. These effects are also more pronounced in the presence of excess silver ions in the solution. It was observed that silver N-(hydroxyethyl)ethylenediaminetriacetic acid and silver nitrilotriacetic acid are not directly reduced by (CH3)2CO•-. This confirms that the redox potential of the silver couple is lowered in the presence of HEDTA and NTA. In addition, HEDTA stabilizes silver metal particles against corrosion due to the shift in the redox potential. Silver particles prepared by γ irradiation and combined with hydrothermal treatment were characterized using transmission electron microscopy and showed particle sizes of 10−20 nm.

Gas Desulfurization with Ferric Chelates of EDTA and HEDTA: New Model for the Oxidative Absorption of Hydrogen Sulfide

The experimental data of Wubs and Beenackers (AIChE J. 1994, 40 (3), 433−444) on the oxidative absorption of H2S into aqueous solutions of ferric chelates of ethylenediaminetetraacetic acid (EDTA) and hydroxyethylethylenediaminetriacetic acid (HEDTA) were reinterpreted using a new penetration model for mass transfer parallel to chemical reaction. Different from the discussion by Wubs and Beenackers (1994), which was based on general, approximate models for the reactive absorption of gases into liquids, it now appears that the diffusivity of ferric chelates of EDTA and HEDTA are in good agreement with the values determined from the reactive absorption of molecular oxygen into aqueous solutions of ferrous EDTA and HEDTA (Wubs and Beenackers, Ind. Eng. Chem. Res.1993, 32, 2580−2594). Also, it now appears that the data from Wubs and Beenackers (1994) are compatible with ferric chelate complex equilibrium constants, reported elsewhere (for instance, Martell and Smith, Critical Stability Constants, 1982). Reinterpretation of the absorption data from Wubs and Beenackers (1994) resulted in the following kinetic rate constants (T = 293 K, CFe(III) = 78 mol/m3 and 2 ≤ pH ≤ 9): EDTA, monohydroxylated complex, 250 ≤ k1,1 ≤ 300 m3/(mol s); HEDTA, monohydroxylated complex, 1.4 ≤ k1,1 ≤ 1.6 m3/(mol s); HEDTA, dihydroxylated complex, 550 ≤ k1,1 ≤ 650 m3/(mol s); for the reaction rate expressed by −RH2S = k1,1CH2SCFe(III).

Studies on the mechanism of chelate degradation in iron-based, liquid redox H2S removal processes

Available data on the oxidation of nitrilotriacetic acid (NTA), ethylenedinitrilotetraacetic acid (EDTA), N-hydroxyethylethylenediaminetriacetic acid (HEDTA), and other aminopolycarboxylate chelating agents are reviewed and the intermediates and products of the oxidative degradation of each chelating agent are described and compared. The oxidation of these chelating agents occurs during the reoxidation of the ferrous chelate to the ferric chelate, during which a Fenton type side reaction occurs in which hydrogen peroxide is formed and which in turn generates the hydroxyl radical by reaction with ferrous ion. The site of oxidative attack by the hydroxyl radical on these ligands seems to be the -CH2- groups α to the carboxylate groups, as well as the -CH2- groups in the ethylene bridges between the nitrogens. The evidence for the implication of the hydroxyl radical as the active oxidant is discussed, and the use of phenyl-tert-butylnitrone (PBN) as the trapping agent for the hydroxyl radical is described. The use of chelating agents as Fe3+/Fe2+redox catalysts for the oxidation of H2S to sulfur that are less reactive toward the hydroxyl radical is recommended. Keywords: chelate degradation, H2S oxidation, nitrilotriacetic acid (NTA), ethylenedinitrilotetraacetic acid (EDTA), N-hydroxyethylethylenediaminetriacetic acid (HEDTA).

Kinetics of H2S absorption into aqueous ferric solutions of edta and hedta

AbstractKinetics of the reaction of hydrogen sulfide with ferric chelates of ethylenediaminetetraacetic acid (EDTA) at 22°C and with ferric chelates of hydroxyethyle‐thylenediaminetriacetic acid (HEDTA) from 21°C to 60°C were studied in a stirred cell reactor under industrial conditions. Concentration of the ferric chelates ranged from 40 to 150 mol/m3 and the pH was varied from 4 to 10. Only the hydroxy forms of the ferric chelates appear to react with hydrogen sulfide. Under the conditions applied, the reaction appeared to be first‐order in hydrogen sulfide and first‐order in hydroxy ferric chelate. At 22°C the rate constant for the EDTA complex is 14–21 m3/mol·s. Uncertainty in this constant is due to the characteristics of the EDTA complex at pH values above 7. For the HEDTA complex, the activation energy of the reaction of hydrogen sulfide with the monohydroxy ferric chelate is (26.4 ± 0.6) kJ/mol with k = 1.8 m3/mol·s at 25°C. The rate constant for the reaction with the dihydroxy ferric chelate is (300 ± 150) m3/mol·s in the temperature range investigated.

The mechanism of the intramolecular rearrangement of HEDTA metal complexes—the dynamic NMR study

Abstract The 1 H NMR spectra of the complexes of K, Mg, Ca, Sr, Ba and Zn ions with N -hydroxyethyl ethylenediaminetriacetic acid were measured at various temperatures. The chemical shifts of the protons on acetates and the backbone change with temperature, while those of the hydroxyethylenic protons do not, and the AB quartet arising from the single acetate coalesces into a singlet with the increase of temperature. The mechanism of the intramolecular rearrangement of the metal HEDTA complexes involves a complex process in which the Δ, Λ conversion and nitrogen inversion occur almost in the same time. It was found that the stability of these metal complexes decreases in the order Zn > alkaline earth metal > K, which is in agreement with the order of the ionic potential of the central ions.

Investigation of N-Methyl-D-Glucamine Buffer for Assay of Alkaline Phosphatase in Serum

We evaluated N-methyl-D-glucamine (MEG) as a buffer for assay of alkaline phosphatase (ALP; EC 3.1.3.1) and compared the MEG-based assay with the current International Federation of Clinical Chemistry Reference Method for ALP (IFCC/RM/ALP), in which 2-amino-2-methyl-1-propanol (AMP) is the pH buffer. The ALP assay in MEG at 30 and 37 degrees C shows excellent correlation with the IFCC/RM/ALP at 30 degrees C, but yields proportionately higher ALP activities (8.2% at 30 degrees C and 57% at 37 degrees C). ALP is unstable in both MEG and AMP at 37 degrees C. Serum incubated in MEG undergoes a pH-dependent biphasic loss of ALP activity: an initial rapid 5% loss after 1 min of incubation and a 10% loss per hour thereafter. A similar pattern was seen for incubation with AMP. The use of a serum-initiated reaction (no preincubation of enzyme with buffer) eliminated the early loss in activity. The addition of the metal ion buffer N-hydroxyethylethylenediaminetriacetic acid, along with low concentrations of Zn and Mg, as used in the IFCC/RM/ALP, reduced the slow loss in activity over time, as did decreasing the reaction temperature to 30 degrees C, but had no effect on the early rapid decay in activity seen in the first minute. Moderate transphosphorylation (45%) and nonenzymatic hydrolysis (3.3 U/L) were observed with MEG under the conditions of the assay (37 degrees C). A comparison of different lots of MEG from two manufacturers showed no significant difference in ALP activities.

Kinetics and mechanism of reaction between aminopolycarboxylatomanganate(III) complexes and cyanide ions: a reinvestigation of the MnCyDTA-CN? reaction

Reactions between CN− and complexes of MnIII withtrans-1, 2-diaminocyclohexanetetraacetic acid (CyDTA) and hydroxyethylethylenediaminetriacetic acid (HEEDTA) have been studied spectrophotometrically at the λmaxS of their respective hydroxo species under pseudo-first-order conditions. The forward reaction is found to be first-order with respect to both the metal complex and [CN−].

Critical Current Densities in Superconducting Y–Ba–Cu–O Prepared by Chelating Method

The critical current of superconducting Y–Ba–Cu–O (YBCO) compounds prepared by the chelating method was investigated. The chelating agents used for this study were iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and triethylenetetraminehexaacetic acid (TTHA). The precursor YBCO obtained from metal complexes heving large stability constants, such as HEDTA, EDTA, DTPA, and TTHA, had very fine and homogeneous particles. The critical current density of YBCO in a block of 1×4×15 mm3 which was sintered at 880∼910°C for 24 h, and then anealed at 500°C in O2 flow was estimated to be 500 A/cm2 at 77 K in zero applied magnetic field.

The kinetics and mechanism of the reaction of H 2O 2 with K[Ru III(PDTA-H)Cl]·2H 2O and K[Ru III(HEDTA-H)Cl

The kinetics and mechanism of the reaction of H 2O 2 with K[Ru III-(PDTA-H)Cl]·2H 2O 1 (L = propylenediaminetetraacetic acid) and K[Ru III(HEDTA-H)Cl] 2 (L = hydroxyethylethylenediaminetriacetic acid) was studied by stopped flow spectrophotometry at pH = 3.4 and μ = 0.1 M (KCl) at various concentrations of H 2O 2 and at different temperatures. The μ-peroxo complex [Ru IVL] 2O 2 (L = PDTA 3, HEDTA 4) was found to be the final product in both cases. The formation of μ-peroxo complexes 3 and 4 was first order in H 2O 2 and Ru IIIL complex concentrations. The values of thermodynamic as well as activation parameters for the interaction of H 2O 2 with Ru IIIL complexes are reported.

Preparation of Superconducting Y–Ba–Cu–O and Bi–Pb–Sr–Ca–Cu–O Compounds by Chelating Method

Superconducting Y–Ba–Cu–O (YBCO) and Bi–Pb–Sr–Ca–Cu–O (BPSCCO) compounds were prepared by a chelating method with various chelating agents, such as nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA) and ethylenediaminetetraacetic acid (EDTA). Above 600°C, the precursors YBCO and BPSCCO turned into a mixture of metal oxides and BaCO3, which finally transformed into the almost single phase of YBCO at 850∼930°C and into the high-Tc phase of BPSCCO at 840°C. The critical current densities of YBCO and BPSCCO in blocks of 1*4*15 mm3 were estimated to be as high as 350 and 500 A/cm2 at 77 K, respectively.

Investigation of the vanadium(III)/vanadium(II)/ N-(hydroxyethyl)ethylenediaminetriacetic acid system by cyclic voltammetry and differential pulse polarography

Cyclic voltammetry and differential pulse polarography (d.p.p.) are used to study the influence of pH and metal complex concentration on the voltammetric responses of the V(III)/V(II)/ N- (hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) system. The monomer-dimer equilibrium of V(III)HEDTA gives rise to typical patterns on cyclic voltammograms. The formation constant for (V(III)HEDTA) 2 is evaluated by d.p.p. The dimer-monomer concentration ratios representing the equilibrium in the bulk solution can be obtained only when the drop time of the mercury electrode is ⩽0.2 s. The pH-independent value of the half-wave potential for the reduction of V(III)HEDTA to V(II)HEDTA is used to evaluate the ratio of the formation constants of V(III)HEDTA and V(II)HEDTA. The suitability of V(III)HEDTA as a model complex for V(III) in ascidians (primitive marine organisms) is discussed.

Rat mast cells permeabilized with Sendai virus secrete histamine in response to Ca2+ buffered in the micromolar range.

In the presence of low extracellular Ca2+, Sendai virus generates permeability lesions in the membrane of rat mast cells. This causes leakage of intracellular phosphorylated metabolites and lactate dehydrogenase; it also permits uptake of normally impermeant aqueous solutes such as the complex of Ca2+ with N-hydroxyethylethylenediaminetriacetic acid. We have used this system to buffer the concentration of cytosol Ca2+ in the micromolar range and thus to cause release of the contents of the secretory granules such as histamine and beta-N-acetylglucosaminidase. We argue that such release occurs by a normal exocytotic secretory mechanism for the following reasons. (1) While leakage of cytosol components is progressively inhibited by Ca2+ in the range 1-10 microM, release of histamine is dependent on Ca2+ in this range. Higher concentrations of Ca2+ are inhibitory to both permeabilization and histamine release. (2) While leakage of phosphorylated metabolites is enhanced in metabolically inhibited cells and the leakage of lactate dehydrogenase is insensitive to metabolic inhibition, the release of histamine and beta-N-acetylglucosaminidase is strictly dependent on an intact metabolic process.

A lead-207 nuclear magnetic resonance study of the complexation of lead by carboxylic acids and aminocarboxylic acids

The complexation of Pb(II) by carboxylic acids and aminocarboxylic acids was studied by 207Pb NMR. The results indicate that the 207Pb chemical shift provides a sensitive probe of the aqueous coordination chemistry of Pb(II). A single, exchange-averaged resonance is observed for lead in solutions containing Pb(NO 3) 2 and pivalic acid, acetic acid, formic acid, or chloroacetic acid, the chemical shift of which is sensitive to the Pb(NO 3) 2 to carboxylic acid ratio and to solution pH. Formation constants for the Pb(II)-carboxylate complexes were determined by fitting the chemical shift data to a model involving the complexes and ligand protonation. Chemical shift data for solutions containing Pb(NO 3) 2 and glycine, histidine, or glycylglycine indicate complexation of Pb(II) by the zwitterionic forms of these ligands. Formation constants for these complexes, which are difficult to study by other methods, were also determined from the chemical shift data. Complexation of Pb(II) by ethylenediaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid, and N-methyliminodiacetic acid causes a large deshielding of the 207Pb nucleus, e.g., the resonance for the ethylenediaminetetraacetic acid complex is deshielded by 2350 ppm. The chemical shift of the lead in these complexes is sensitive to protonation of the complex and to the formation of mixed complexes containing hydroxide ion.

The effects of thiosalicylic and hydroxyethylethylenediaminetriacetic acids on the absorption and excretion of 54Mn and 65Zn in the duodenally dosed sheep.

Nine sheep, each prepared with a single cannula in the ascending duodenum and a reentrant cannula in the terminal ileum were fed a purified diet deficient in manganese and zinc for a period of 1 month. The sheep were then divided into three equal groups and duodenally dosed with a mixture containing MnSO4, ZnSO4, 54Mn, 65Zn, and water (control), thiosalicylic acid (TSA), or hydroxyethylethylenediaminetriacetic acid (HEDTA). Blood and ileal digesta were sampled for 24 h and total urine and feces were collected for 14 days after dosing. Plasma uptake of 54Mn 1 h after dosing was more than threefold higher in the HEDTA-dosed sheep than in other sheep, indicating higher absorption of 54Mn. This was accompanied by a lower flow of 54Mn through the terminal ileum during the first 12 h after dosing. However, total 14-day urinary and fecal excretion of 54Mn and 65Zn were apparently higher in the HEDTA-dosed sheep than in other sheep, each approaching 100% of the dose. Excretion of 54Mn and 65Zn in TSA-dosed sheep was apparently higher than in control sheep. Plasma uptake 65Zn was higher in TSA-dosed sheep and lower in HEDTA-dosed sheep than in control sheep. However, total 14-day excretion of 65Zn in feces and urine was slightly higher in TSA-dosed than in control sheep. It was concluded that chelation of Mn and Zn with HEDTA or TSA would aggravate rather than alleviate a Mn or Zn deficiency in sheep.

Acceleration of the copper-catalyzed autoxidation of cysteine by ethylenediaminetetraacetic acid and related polyaminopolycarboxylic acids.

Polyaminopolycarboxylic acid with at least two ligand nitrogens such as ethylenediaminetetraacetic acid accelerates the copper-catalyzed autoxidation of cysteine. The extent of acceleration of the reaction is related to the stability constant of the Cu (II) chelate of the polyaminopolycarboxylic acid. N-Hydroxyethylethylenediaminetriacetic acid, N-hydroxy-1, 3-diaminopropanetetraacetic acid and ethyleneglycol-bis-(β-aminoethylether) tetraacetic acid are the most potent accelerators and those chelating agents have the stability constants of approximately 1017.5. Addition of a sufficient excess of the chelating agent over cysteine retards the oxidation.

The reaction of vanadium(v) with hydroxyethylethylenediamine triacetic acid

1. Complex formation in a solution of vanadium(V) with hydroxyethylethylenediaminetriacetic acid has been studied spectrophotometrically, and the composition and instability constant of the complex have been determined. 2. The rate of oxidation of hydroxyethylethylenediaminetriacetic acid in vanadium(V) solutions is first order with respect to concentrations of vanadium(V) and the acid. The order with respect to hydrogen ion is variable and fractional, the activation energy being 20.4±0.2 kcal/mole.

Spectrophotometric study of the complexes of hydroxyethylethylenediaminetriacetic acid with bismuth(III), copper(II) and lead(II)

The bismuth(III), copper(II) and lead(II) hydroxyethylethylenediaminetriacetic acid systems were investigated in detail. Evidence for the formation of species BiX, Bi(OH)X −, CuHX, CuX −, PbHX and PbX − is presented and their stability constants given.

Hydrate compositions of hydroxyethylethylenediaminetriacetates of the rare-earth elements

1. Complexes of the REE, Y, and Sc with hydroxyethylethylenediaminetriacetic acid have been isolated in solid form. The hydrate compositions of the complexes have been determined. 2. The La and Pr complexes form hydrates of different compositions. The LnL hydrates form slightly nonisostructural groups in the series La-Lu. 3. According to thermographic analysis data, the hydrate water in the LnL·nH2O complexes of different hydrate compositions is not bonded with the same firmness.