The enthalpies of interactions of Ca2+(aq) and C2O 4 2− (aq) ions in complexon solutions: Competition between complexation and precipitation

The thermal effects of mixing of aqueous calcium chloride with sodium citrate and ethylenedi-aminetetraacetate in the absence and presence of sodium oxalate have been measured at 25°C. The thermal effects of dilution of aqueous calcium chloride solutions were determined. The thermal effects of calcium oxalate precipitation and formation of calcium complexes with citrate and ethylenediaminetetraacetate ions were calculated. The 1% solution of sodium citrate inhibited the formation of CaC₂O₄ (s); in a 1% solution of sodium ethylenediaminetetraacetate with [Ca²⁺][C₂O ₄ ^2? ] > 10^?5, the endothermal formation of the [CaEdta]^2? complex quickly changed to exothermal precipitation. The 3 and 5% solutions of complexons showed a pronounced inhibiting effect on the formation of urinary stones even when the concentration of calcium and oxalate ions in solution exceeded the product of solubility of CaC₂O₄ by four and more orders of magnitude.     

Production and Purification of Pectinase from Bacillus subtilis 15A-B92 and Its Biotechnological Applications

Enzymes that degrade pectin are called pectinases. Pectinases of microbial origin are used in juice clarification as the process is cost-effective. This study screened a pectinase-producing bacterium isolated from soil and identified as Bacillus subtilis 15A B-92 based on the 16S rRNA molecular technique. The purified pectinase from the isolate showed 99.6 U/mg specific activity and 11.6-fold purity. The molecular weight of the purified bacterial pectinase was 14.41 ± 1 kD. Optimum pectinase activity was found at pH 4.5 and 50 °C, and the enzyme was 100% stable for 3.5 h in these conditions. No enzymatic inhibition or activation effect was seen with Fe²⁺, Ca²⁺, or Mg²⁺. However, a slight inhibition was seen with Cu²⁺, Mn²⁺, and Zn²⁺. Tween 20 and 80 slightly inhibited the pectinase, whereas iodoacetic acid (IAA), ethylenediaminetetraacetate (EDTA), urea, and sodium dodecyl sulfate (SDS) showed potent inhibition. The bacterial pectinase degraded citrus pectin (100%); however, it was inactive in the presence of galactose. With citrus pectin as the substrate, the Km and Vmax were calculated as 1.72 mg/mL and 1609 U/g, respectively. The high affinity of pectinase for its substrate makes the process cost-effective when utilized in food industries. The obtained pectinase was able to clarify orange and apple juices, justifying its application in the food industry.     

Étude polarographique du mercure (Hg+2) en présence d'acide éthylènediaminotétracétique: Titrage ampérométrique des cations par le complexon,basé sur la vague de dépolarisation anodique

The anodic depolarization wave of Hg⁺² by complexone (ethylenediaminotetraacetic acid) has been found to be proportional to the concentration of complexone (10^-4 to 10^-3 mole/liter, pH =6.4 in buffered medium). Titrationc of complexone by Mn⁺², Co⁺², Ni⁺², Cd⁺², Mg⁺², Zn⁺² gave, at the same pH of 6.4, normal amperometric curves. On the other hand, alkaline-earth cations, the complexes of which are less stable than the aforementioned ones, gave abnormal amperometric curves in that the height of the wave observed during titration is much larger than the one corresponding to the concentration of the complexone that is not involved in the formation of the complex.These results can nevertheless be interpreted in a satisfactory way by assuming that the measured current is determined on the one hand by diffusion and on the other hand by the rate of dissociation of the complexes in the vicinity of the electrode. The rate constant is greater the less stable the complex.     

Preparation of stable colloidal solution of cadmium sulfide CdS using ethylenediaminetetraacetic acid

By the method of chemical condensation a stable aqueous colloidal solution of nanoparticles of cadmium sulfide was obtained. The solution obtained in the daylight had a bright lemon-yellow color. For the temporary stabilization of the solution was used an organic complexone, disodium ethylenediaminetetraacetate (EDTA), that prevented coagulation of colloidal particles up to several months at 4°C. At room temperature, the solution remained stable during a month. The structure and properties of the disperse phase were studied by the X-ray diffraction, optical fluorescence, and electron microscopy. The solid particles size is about 3 nm, they have a disordered close-packed structure with the space group P6mm and possess the photoluminescence color from green to orange depending on the duration of keeping the solution. The size of coagulates was 10 nm, 100 nm, and 1 μm after keeping for 1, 2, and 4 months, respectively.     

Enzymatic Extraction and Characterization of Pectin from Cocoa Pod Husks (Theobroma cacao L.) Using Celluclast® 1.5 L

Cocoa pod husks are a waste generated during the processing of cocoa beans. We aimed to explore the enzymatic extraction of pectin using cellulases. The extraction process was optimized using a central composite design (CCD) and analyzed by response surface methodology (RSM). The parameters optimized were feedstock concentration (%), enzyme dosage (µL/g), and time (h). Three dependent variables were studied: pectin yield (g/100 g dry husk) (R² = 97.02), galacturonic acid content (g/100 g pectin) (R² = 96.90), and galacturonic acid yield (g/100 g feedstock) (R² = 95.35). The optimal parameters were 6.0% feedstock concentration, 40 µL g⁻¹ of enzyme, and 18.54 h, conditions that produced experimentally a pectin yield of 10.20 g/100 g feedstock, 52.06 g galacturonic acid/100 g pectin, and a yield 5.31 g galacturonic acid/100 g feedstock. Using the chemical extraction method, a yield of 8.08 g pectin/100 g feedstock and a galacturonic acid content of 60.97 g/100 g pectin were obtained. Using assisted sonication, a pectin yield of 8.28 g/100 g feedstock and a galacturonic acid content of 42.77 g/100 g pectin were obtained. Enzymatically optimized pectin has rheological and physicochemical features typical of this biomaterial, which provides an interesting alternative for the valorization of cocoa husks.     

Critical study of metallochromic indicators for calcium

The visual clarity of the colour changes at the end-points in the compleximetric titration of calcium is discussed for the metallochromic indicators, arsenazo-III, calcein, calcon, eriochrome blue black B, methylthymol blue, murexide, phthalein complexone, and thymolphthalein complexone. The colour changes were specified with the help of CIE chromaticity diagrams. The sharpness of the colour changes of the indicators was studied by varying the optical (or colour) concentration. Thymolphtalein complexone and phthalein complexone are shown to be the most appropriate indicators for the visual titration of calcium with EDTA.     

Influence of mechanical properties of pectin films on charge density and charge density distribution in pectin macromolecule

The hydration and mechanical properties of citrus pectin films were examined in conditions relevant to those in the plant cell wall. The pectins used for this study varied in the degree of esterification (DE) (high or low) and charge distribution on the backbone (random or block). The hydration of the films was controlled in an osmotic pressure experiment using polyethylene glycol solutions (PEG 20000). Hysteresis tests at constant deformation rate (stress vs deformation) were used for investigating the mechanical behaviour of films. Mechanical and hydration properties of pectin films were examined as a function of charge density, charge density distribution and counterion environment—K⁺, Ca²⁺, Mg²⁺. Swelling decreased with increasing counterion concentration. The effect is stronger in the case of Ca²⁺ and Mg²⁺ for low esterified pectins and therefore crosslinks from divalent ions could be assumed. The crosslink effect is confirmed in mechanical experiments where an increase in the film tensile modulus is observed with increasing counterion concentration. It is shown for the first time that in case of highly concentrated pectin solutions Mg²⁺ cations also act as a crosslinker for pectin macromolecules.     

Characterization of the complexing agents’ influence on bioscouring cotton fabrics by FT-IR and TG/DTG/DTA analysis

The nature of the complexing agents used in the bioscouring process of cotton fabrics aiming to eliminate the non-cellulosic compounds (pectin, waxes, etc.) and to improve the hydrophilic and wetting properties influences the thermal behaviour and the FT-IR spectra of the textile materials. In this paper, we study the influence of the experimental conditions and complexing agent nature (sodium citrate or disodium EDTA salt) on the pectin elimination in bioscouring treatment of cotton fabric by FT-IR and TG/DTG/DTA analysis. The changes from FT-IR spectra of the specific bands (absorbance intensity at 2916, 2852, 1732 and 1640/1642 cm^?1) were evaluated. The thermal behaviour of the investigated samples’ fabric by using TG/DTG/DTA analysis was studied at 30–600 °C temperature range, in air atmosphere. All samples showed three mass-loss steps due to the elimination of humidity, decomposition of the non-cellulosic and cellulosic components (main degradation stage of the samples) and thermo-oxidative decomposition of the formed degradation products. The T_onset values corresponding to the main decomposition step, the mass-loss values (%Δm) and the % residual mass (at 600 °C) were influenced by the complexing agent nature as well as the concentration and the action time of the commercial enzyme product. In addition, the calcium content of some samples treated with and without ultrasound was determined using atomic absorption spectroscopy method (AAS) in order to correlate the results with TG/DTG/DTA analysis. The obtained results have shown that the synergistic action of experimental conditions (enzyme concentration, pH, enzyme product action time, ultrasound) and the presence of sodium citrate as a biodegradable complexing agent led to the elimination of a higher amount of pectin from the cotton samples than that eliminated when using EDTA.     

Creep study of high-esterified pectin gels

A creep study has been made of 2% pectin gels in the 1∶1 water-glycerol mixture in the temperature interval 284.7 to 321.7 °K, and also of water-glycerol pectin gels concentrated to 2–5% at 290.7 °K. Water-glycerol pectin gels by their thermorheological properties are close to water-sucrose gels studied earlier. It is shown that the rate of the relaxation processes is independent of the concentration. The standard break-down enthalpy of the 2% gel cross-links in the temperature interval where rheological properties are measured, is 17–39 kJ · mole^?1.     

Use of a Tensammetric Wave for the End-Point Detection in Chelatometry

Abstract

A new method for the end-point detection in complexometric titration using a tensammetric wave of organic reagents such as oxine and alizarin complexone (ALC) was studied. The tensammetric wave of these reagents disappears by their chelate formation and reappears by the liberation of free indicator during the exchange reaction between indicator chelate and EDTA. This mechanism is utilized for the end-point detection in complexometric titration of metals. Since the sensitivity of tensammetric wave is extremely high, very sharp end-point can be obtained for the titration of metals even in the concentration of 10^?5M.     

Indirect determination of fluoride in waters with lanthanum alizarin complexone and inductively-coupled plasma emission spectrometry

Fluoride is determined indirectly by measurement of the La II 333.75-nm line in the lanthanum/alizarin complexone/fluoride complex. The ternary complex is extracted into hexanol containing N,N-diethylaniline and the extract is introduced directly into the plasma. Related to water samples, the detection limit (3σ, concentration factor 5) is 0.59 ng ml^?1 fluoride, calibration is linear up to 1.2 μg ml^?1 and the relative standard deviation for 0.04 μg ml^?1 is 2.6%. Alkali, alkali elements and most anions do not interfere. The method is applied in the analysis of river water, coastal seawater and drinking water.     

Microstructure of beta-lactoglobulin/pectin coacervates studied by small-angle neutron scattering

Small-angle neutron scattering (SANS) has been used to investigate the microstructure of beta-lactoglobulin/pectin coacervates prepared by different initial protein/polysaccharide weight ratio (r), sodium chloride concentration (C(NaCl)), and pectin charge density. The higher r and higher pectin charge density lead to higher scattering intensity at small q range (0.007 Angstrom(-1) < q < 0.02 Angstrom(-1)), suggesting that the charges of pectin chains are screened significantly by the binding of oppositely charged protein molecules, leading to a tighter aggregation of pectin chains. On the other hand, the appearance of a shoulder peak at intermediate q range (0.04 Angstrom(-1) < q < 0.2 Angstrom(-1)) is used to interpret the formation of protein domains in beta-lactoglobulin/pectin coacervates. At C(NaCl) = 0.1 M, the coacervate of beta-lactoglobulin and pectin A does not show a shoulder peak at intermediate q range at r = 10:1, suggesting that protein molecules are separately bound on pectin chains. However, a shoulder peak appears at intermediate q range at r = 20:1 and 30:1, and the average protein domain size estimated from the shoulder peak position is 7.2 and 8.5 nm, respectively, for these two coacervates. When C(NaCl) increases from 0.05 to 0.2 M, the shoulder peak shifts toward smaller q and becomes broader, indicating that the addition of a higher amount of salt leads to a more heterogeneous coacervate structure. Pectin B with a lower linear charge density favors the formation of larger protein domains. The formation of protein domains in beta-lactoglobulin/pectin coacervates is partially ascribed to the self-aggregation of beta-lactoglobulin molecules. Two kinds of microstructures of beta-lactoglobulin/pectin coacervates with and without observable protein domains have been proposed.     

“In situ” measurements of the influence of temperature on the decomposition of H2Na2EDTA adsorbed on alumina

The adsorption of H₂Na₂EDTA (disodium salt of ethylenediaminetetraacetic acid) on gamma alumina and its thermal degradation has been investigated by transmission IR. The IR spectra in the 2000–1200 cm⁻¹ region of the supported complexone were analysed in the temperature range 393–673 K utilising IR cell reactor applied for in situ measurements. Based on the observed changes, it can be stated that thermal decomposition of adsorbed complexone occurs in the temperature range of 473–493 K.     

Determination of Fluoride in Water by Reversed-Phase High-Performance Liquid Chromatography using F−-La3+-Alizarin Complexone Ternary Complex

A method for the determination of fluoride by reversed-phase, high-performance liquid chromatography (RP-HPLC) is described. Fluoride, La³⁺ and alizarin complexone form F-La³⁺-alizarin complexone ternary complex, which is separated from the matrix on a RP, Ultrasphere C₁₈ column (250 × 4.6 mm, 5 μm) using methanol-water (19:81, v/v) mobile phase at 1.00 mL min^?1; detection at 568 nm. The calibration graph was linear from 1.0–150 ng mL^?1 for fluoride with a correlation coefficient: 0.9993 (n=6). The detection limit was 0.2 ng mL^?1. The method was successfully applied to the determination of fluoride in river and tap water. Recovery was: 94–102%, RSD in the range: 1.9 –3.6%.     

Mononuclear and homobinuclear vanadium(IV), chromium(III), molybdenum(III), and uranium(VI) chelates with ortho-cresolphthalein complexone

Mononuclear and homobinuclear o-cresolphthalein complexone complexes with VO²⁺, Cr³⁺, MoO⁺, and UO₂ ²⁺ have been prepared and their structures investigated. The empirical formulas, the mode of bonding, and the geometry of the complexes were obtained from elemental and thermal analyses, IR, electronic and ESR spectra, magnetic moment determinations, DC and CV polarographic studies.     

Theoretical analysis of systems of chelation chromatography upon irradiation

The changes that occur under conditions of irradiation in a chromatographic system were considered with the use of a mathematical model for eluents with a wide pH range at constant concentration of complexone. The effect of the concentration of complexone and the behavior of individual components of the mixture under separation were studied at constant pH. The character of the change in the concentrations and pH values in eluates was determined. Experimental data obtained earlier were interpreted on the basis of the above considerations.     

Bismuthiol II as an analytical reagent

Summary Silver can be separated as its Bismuthiol II complex from OsO_{4 4} ^2– , Os⁴⁺, Ir⁴⁺, Ru³⁺, Rh³⁺ with thiosulphate or complexone III as the masking agent at a p_H between 5 and 9. Au³⁺ can be kept in solution only by thiosulphate at a p_H 8–9 and cyanide complexes palladium at a P_H of about 6. Separation from platinum in presence of a mixture of tartaric acid and complexone III is possible only to a limited extent.Part VI see Z. analyt. Chem. 155, 86 (1957)     

Synthesis and acid-base and complex-forming properties of 1,4,7,10-tetrakis(dihydroxyphosphorylmethyl)-1,4,7,10-tetraazacyclododecane

Conclusions A new complexone, 1,4,7,10-tetrakis(dihydroxyphosphorylmethyl)-1,4,7,10-tetraazacyclododecane, has been synthesized and its acid-base and complex-forming properties have been studied. It shows a very high complexing capability and marked selectivity for cations of large ionic radius (Cd²⁺, Hg²⁺, Pb²⁺, La³⁺).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 844–849, April, 1984.     

Novel method for the preparation of core-shell nanoparticles with movable Ag core and polystyrene loop shell

Core/shell nanoparticles with movable silver (Ag) core and polystyrene (PSt) shell (Ag@PSt nanoparticle) were successfully synthesized at room temperature and under ambient pressure via two steps: γ-irradiation and interfacial-initiated polymerization. Firstly, mono-dispersed Ag nanoparticles with diameters 20 nm were synthesized in inversed microemulsion by reducing silver nitrate under γ-irradiation. Then, Ag nanoparticles were coated with PSt via interfacial-initiated polymerization with cumene hydroperoxide/ferrous sulfate/disodium ethylenediaminetetraacetate/sodium formaldehyde sulfoxylate (CHPO-Fe²⁺-EDTA-SFS) as the redox initiation pair. The resulted Ag@PSt nanoparticles were identified by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).     

Thermodynamics of Ternary Complex Formation of Copper(II) and Nickel Iminodiacetates with Histidine in Solution

Calorimetric, potentiometric and spectrophotometric studies on the mixed–ligand complexes of copper(II) with nickel iminodiacetates (Ida) and histidine (His) have been carried out in aqueous solution at 298.15 K and ionic strength I = 0.5 mol·dm^?3 (KNO₃). The thermodynamic parameters of formation of various mixed complexes have been determined. The probable coordination modes of the complexone and histidine residues in the mixed ligand complexes are discussed.