Adsorption of Hg(II) Ions onto Binary Biopolymeric Beads of Carboxymethyl Cellulose and Alginate

The removal of Hg(II) ions from aqueous solution by adsorption onto cross-linked polymeric beads of carboxymethyl cellulose (CMC) and sodium alginate was studied at fixed pH (6) and room temperature 28 ± 0.2°C. The cross-linked polymeric beads were characterized by FTIR spectra. Sorption capacity of the polymer for the mercury ions was investigated in aqueous media consisting different amounts of mercury ions (2.5 to 100 mg dm^?3) and at different pH values (2 to 8). Adsorption behavior of Hg(II) ions could be modeled using both the Langmuir and Freundlich isotherms. The dynamic nature of adsorption was quantified in terms of several kinetic constants such as rate constants for adsorption (k₁) and Lagergreen rate constant (K_ad). The influence of various experimental parameters such as effect of pH, contact time, solid-to-liquid ratio, salt effect, and temperature effect etc. were investigated on the adsorption of Hg(II) ions.     

Improving the high variable bioavailability of griseofulvin by SEDDS

To enhance the dissolution and oral absorption of poorly water-soluble griseofulvin (GF), self-emulsifying drug delivery system (SEDDS) composed of oil, surfactant and cosurfactant for oral administration of griseofulvin was formulated, and its physicochemical properties and pharmacokinetic parameters were evaluated. The solubility of griseofulvin was further improved by the addition of hydrochloric acid. Droplet size of griseofulvin emulsion was kept constant both in simulated gastric fluid without pepsin and simulated intestinal fluid throughout 12 weeks incubation period. Griseofulvin in the SEDDS rapidly dissolved in different dissolution media. This was not the case for the commercial GRIS-PEG tablets. In different fed diet groups, AUC 0-->24 h, Cp max, and T max of griseofulvin after oral administration of SEDDS in rats were comparable to those after oral dose of GRIS-PEG tablet. Although, in fed lipidic diet group, the mean AUC and Cp max after oral administration of GRIS-PEG in rats were 1.28 and 1.15 fold higher, respectively, compared with those of SEDDS, these have not shown to be significantly different. These results demonstrate that the SEDDS of griseofulvin composed of Capmul GMO-50, Poloxamer and Myvacet 9-45 greatly enhanced the dissolution of griseofulvin (without ultramicronisation). However, food intake effect on the bioavailability of griseofulvin has remained. Thus, this system may provide a useful dosage form for oral water-insoluble drugs which have problems in their dissolution.     

Ion-exchange properties of silica gel with covalently bonded histidine

The ion-exchange and acid-base properties of Silasorb 600 (10 μm) with immobilized histidine (His-SiO₂) were investigated. The acid-base properties of the sorbent were estimated from the dependence sof the retention of organic acids and bases on the eluent pH. The effect of various organic modifiers (benzoic, citric, oxalic, and sulfuric acids) and the eluent pH on the retention of inorganic ions was studied. It was shown that His-SiO₂ exhibits anion-exchange properties in acidic and weakly acidic media at pH < 5.7. Eight anions were separated under optimal conditions on a 150 × 4.6-mm column in 21 min using a 5 mM oxialic acid solution as an eluent.     

Formulation,Characterization and Permeability Studies of Fenugreek (Trigonella foenum-graecum) Containing Self-Emulsifying Drug Delivery System (SEDDS)

Fenugreek is used as a spice and a traditional herbal medicine for a variety of purposes, given its antidiabetic and antioxidant effects. Self-emulsifying drug delivery systems (SEDDS) of herbal drugs are targets of extensive research aiming to increase bioavailability and stability. The study’s objective was to formulate SEDDS containing Trigonella foenum-graecum extract to improve the stability of herbal extract and to increase their permeability through a Caco-2 monolayer. A characterized fenugreek dry extract was used for the formulations, while the SEDDS properties were examined by particle size analysis and zeta potential measurements. Permeability assays were carried out on Caco-2 cell monolayers, the integrity of which was monitored by follow-up trans-epithelial electric resistance measurements (TEER). Cytocompatibility was tested by the MTT method, and an indirect dissolution test was performed, using DPPH antioxidant reagent. Two different SEDDS compositions were formulated from a standardized fenugreek dry extract at either the micro- or the nanoemulsion scale with sufficient stability, enhanced bioavailability of the compounds, and sustained release from HPMC capsules. Based on our results, a modern, non-toxic, cytocompatible fenugreek SEDDS formulation with high antioxidant capacity was developed in order to improve the permeability and bioavailability of all components.     

Effect of pH and washing on calcium and magnesium distribution between pulp and filtrate

The impact of pH and washing procedure on calcium and magnesium distribution between pulp and filtrate in pulp processing was investigated. Depending on media pH, the elements are present in the form of ions (Ca²⁺, Mg²⁺) and hydrated oxides (Ca(OH)₂, Mg(OH)₂). Distribution was monitored using binary systems of CaCl₂ and MgCl₂ dissolved in deionized water or Ca²⁺ and Mg²⁺ ions present in filtrates from an industrial pulp mill. Complying with the relevant standards in force, Ca and Mg contents are expressed as CaO and MgO. The study was aimed at obtaining mathematic relations between pH and calcium and magnesium, as two important non-process elements, sorption on pulp. Distribution of the elements between pulp and liquid (filtrate or water) was determined with analytical procedures and simulation of pulp washing. It was found that both pH and filtrate composition influenced sorption/desorption of the elements on/from pulp. Filtrate from a pulp mill, mainly content of organic substances in liquid phase, affects their sorption on pulp and desorption to liquid. The higher the pH value the more efficient the sorption of the elements, magnesium being sorbed on pulp in higher amounts than calcium. Prevalence of the sorbed magnesium is preserved even at lower concentrations of both elements. Distribution of the elements between pulp and solution is expressed through mathematic relations which, in turn, can be employed to purposefully modify or optimize the distribution between the solid (pulp) and liquid (filtrate) media. Moreover, rationalized exploitation of mathematical relations enables balancing the elements within a cellulose manufacture, regulating media recycling, and predicting an eventual impact on technological processes.     

Development and tailoring of amino-functionalized activated carbon based Cucumerupsi manni Naudin seed shells for the removal of nitrate ions from aqueous solution

The removal of nitrate ions with ethylenediamine (EDA)-functionalized activated carbon (AC-NH₂) was studied in this work. Activated carbon prepared from Cucumerupsi manni Naudin seed shells using ZnCl₂ (ACZ) was functionalized with EDA via a nitric acid oxidation followed by acyl chlorination and amidation process. The effect of pH, contact time, initial concentration and co-existing ions on the adsorption of nitrate ions have been investigated. The FTIR and elemental analysis revealed that amino groups were successfully grafted onto the ACZ after functionalization. The surface area and average pore of ACZ were found to be 1008.99 m²/g and 2.02 nm respectively. However, it was noticed that, after functionalization (AC-NH₂), its surface area decreases to 113.43 m²/g meanwhile, its pore diameter increases to 2.48 nm. The experimental results of adsorption showed that AC-NH₂ exhibit excellent nitrate ions uptake performance compared to ACZ which is attributed to the presence of the grafted amino groups on the ACZ. Nitrate adsorption follows pseudo-first-order kinetic model while the equilibrium adsorption data was best fitted the Freundlich isotherm suggesting that the adsorption process was predominated by physisorption. This study demonstrates that the prepared AC-NH₂ is a promising adsorbent for nitrate ions removal from aqueous media.     

The solubility of ozone and kinetics of its chemical reactions in aqueous solutions of sodium chloride

The solubility of ozone and the kinetics of its decomposition and interaction with chloride ions in a 1 M aqueous solution of NaCl at 20°C and pH 8.4–10.8 were studied. The ratio between the concentration of O₃ in solution and the gas phase was found to be 0.16 at pH 8.4–9.8. The concentration of dissolved ozone decreased sharply as pH increased to 10.8 because of a substantial increase in the rate of its decomposition. It was observed for the first time that the interaction of O₃ with Cl^? in alkaline media resulted in the formation of ClO ₃ ^? chlorate ions. The dependence of the rate of formation of ClO ₃ ^? on pH was determined; its maximum value was found to be 9.6 × 10^?6 mol l^?1 min^?1 at pH 10.0 and the concentration of ozone at the entrance of the reactor 30.0 g/m³. A spectrophotometric method for the determination of chlorate ions (concentrations 1 × 10^?5?3 × 10^?4 M) in aqueous solutions was suggested.     

Synthesis and characterization of 2, 4-dihydroxy-benzaldehydeoxime-formaldehyde polymers and their application as ion-exchangers

Polymers were prepared by the condensation of 2, 4-dihydroxybenzaldehydeoxime (2, 4-DBO) and formaldehyde (F) in the presence of oxalic acid as catalyst with varying molar ratios of reacting monomers. Polymers were characterized by their IR spectra, elemental analyses, TGA and M_n as determined by vapour pressure osmometry as well as by non-aqueous conductometric titrations. Viscosity measurements of the solutions of polymer samples were carried out in dimethylformamide. Chelation ion-exchange properties have also been studied employing the batch equilibration method. This method involved the measurement of distribution of a given metal between the polymer sample and a solution containing metal ions. The study was carried out over a wide pH range and in media of various ionic strengths. The polymer showed a higher selectivity for UO ₂ ²⁺ and Fe³⁺ ions than for Cu²⁺, Ni²⁺, Co²⁺ and Mn²⁺ ions.     

ESI-MS study of the mechanism of glycyl-l-histidyl-l-lysine-Cu(II) complex transport through model membrane of stratum corneum

In mammalian organisms copper can be found mainly in the form of complex with specific tripeptide, GHK-Cu (glycyl-l-histidyl-l-lysine-Cu(II)). GHK-Cu is the basic form in which copper is transported in tissues and permeates through cell membranes. The penetration ability of GHK-Cu through the stratum corneum and its role in copper ions transport process is the key issue for its cosmetic and pharmaceutical activity. The permeability phenomenon was studied by use in vitro model system—Flynn diffusion cell with the liposome membrane.The earlier studies on the influence of different ligands on the migration rate of copper ions through model membrane provide evidence for hampering role of ligands structure and pH of formulations in this process.Structures of copper complexes formed in solutions of different pH media were evaluated by use of ESI-MS. The permeability coefficients of copper complexes increase with increasing pH. It was proved that only tripeptide GHK and its complexes with copper: GHK-Cu and (GHK)₂-Cu are able to migrate through membrane model of stratum corneum.     

Organic acid solutions in the chromatography of inorganic ions. V. Thin-layer chromatography in tartrate-water-ethanol media

Summary We present a study of the chromatographic behaviour of sixty inorganic ions on cellulose thin layers, employing acidic solutions of tartaric acid-water-ethanol at its own pH and basic solutions of tartaric acid-water-ethanol-NH₄OH at about pH 9 as eluents. Generally the ions show a decreasing migration rate with increasing percentage of ethanol, at constant tartrate molarity, in acidic and basic solutions. For some ions the decrease in migration rate is the same in acidic and basic media, for others with a complexing capacity it is greater in basic than in acidic media. Some interesting separations are shown.This work has been in part supported by C.N.R. of Italy.     

Synthesis of Two N,N′-bis(N,N-dialkylamide) Derivatives of Diethylenetriaminepentaacetic Acid and the Stabilities of Their Complexes with Gd3+, Ca2+, Cu2+, and Zn2+

Two bis(N,N-dialkylamide) derivatives of DTPA [(carboxymethyl)iminobis (ethylenenitrilo) tetraacetic acid], DTPA-BDMA = the bis(N,N-dimethylamide) and DTPA-BDEA = the bis(N,N-diethylamide) 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. Stability and selectivity constants were measured to evaluate the possibility of using the corresponding gadolinium(III) complexes for magnetic resonance imaging contrast agents. The stability constants of gadolinium(III), copper(II), zinc(II), and calcium(II) complexes with DTPA-BDMA and DTPA-BDEA were investigated quantitatively by potentiometry. The stability constant for gadolinium(III) complexes is larger than those for Ca(II), Zn(II), and Cu(II) complexes. The selectivity constants and modified selectivity constants of the amides for Gd³⁺ over endogenously available metal ions were calculated. Effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media is assessed by comparing pM values at physiological pH 7.4. Spin-lattice relaxivity values R₁ for Gd(III) complexes were also determined. The observed relaxivity values were found to decrease with increasing pH in the acid range below pH 4 and relaxivity values became invariant with respect to pH changes over the range of 4–10. ¹⁷O NMR shifts showed that the [Dy(DTPA-BDMA)] and [Dy(DTPA-BDEA)] complexes had one inner-sphere water molecule. Water proton spin-lattice relaxation rates for the [Gd(DTPA-BDMA)] and [Gd(DTPA-BDEA)] complexes were also consistent with one inner-sphere gadolinium(III) coordination position.     

Three dimensional graphene transistor for ultra-sensitive pH sensing directly in biological media

In this work, pH sensing directly in biological media using three dimensional liquid gated graphene transistors is presented. The sensor is made of suspended network of graphene coated all around with thin layer of hafnium oxide (HfO₂), showing high sensitivity and sensing beyond the Debye-screening limit. The performance of the pH sensor is validated by measuring the pH of isotonic buffered, Dulbecco's phosphate buffered saline (DPBS) solution, and of blood serum derived from Sprague-Dawley rat. The pH sensor shows high sensitivity of 71 ± 7 mV/pH even in high ionic strength media with molarities as high as 289 ± 1 mM. High sensitivity of this device is owing to suspension of three dimensional graphene in electrolyte which provides all around liquid gating of graphene, leading to higher electrostatic coupling efficiency of electrolyte to the channel and higher gating control of transistor channel by ions in the electrolyte. Coating graphene with hafnium oxide film (HfO₂) provides binding sites for hydrogen ions, which results in higher sensitivity and sensing beyond the Debye-screening limit. The 3D graphene transistor offers the possibility of real-time pH measurement in biological media without the need for desaltation or sample preparation.     

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

To quantify the properties of protic ionic liquids (PILs) as acid–base reaction media, potentiometric titrations were carried out in a neat PIL, ethylammonium nitrate (EAN). A linear relationship was found between the 14 pK_a values of 12 compounds in EAN and in water. In other words, the pK_a value in EAN was found to be roughly one unit greater than that in water regardless of the charge and hydrophobicity of the compounds. It is possible that this could be explained by the stronger acidity of HNO₃ in EAN than that of H₃O⁺ in water and not by the difference in the solvation state of the ions. The pH value in EAN ranges from ?1 to 9 on the pH scale based on the pH value in water.     

Study of the state of95Zr+95Nb in aqueous solutions

The adsorption on paraffine and polyethylene and the paper chromatography in aqueous solutions in the pH range of 2–12 were used for the study of the behaviour of⁹⁵Zr and⁹⁵Nb. The effect of complexing ions (SO ₄ ^2? and CO ₃ ^2? ) was studied in the same pH range. The constants of hydrolysis and the composition of hydrolytic species of⁹⁵Zr in the solution containing sulphate ions were determined in the pH range of 1–2. The paper chromatography was used for the control of the purity of⁹⁵Zr after an extractive separation from⁹⁵Nb with α-benzoinoxime. The possibility of studying the extraction processes of Zr (without its previous separation from Nb) by reversed phase chromatography is shown. Conditions for the formation of polynuclear compounds of Zr and Nb and their influence on the extraction separation in nitrate media were studied.     

Electrosurface Properties of Hydr(oxides) and Oxide Nanostructures in 1 : 1 Electrolyte Solutions: 1. Adsorption Characteristics of Boehmite, Goethite, and Silicon Dioxide

The adsorption of potential-determining ions on aluminum and iron hydroxides and silicon dioxide was measured in KCl and NaCl background solutions. It was shown that dependences of the adsorption on pH and the concentration of a background 1 : 1 electrolyte (NaCl) have the shape characteristic of oxide surfaces; the of values pH_PZCwere determined. Results of adsorption measurements were used for the determination of constants of surface reactions and adsorption potentials of ions in terms of the 2-pK model.     

Imprinted polymer particles for iron uptake: Synthesis, characterization and analytical applications

This work reports the preparation of molecularly imprinted polymer particles for selective extraction and determination of iron ions from aqueous media. The polymer particles were synthesized from Fe(NO₃)₃, morin, 4-vinylpyridine, ethyleneglycoldimethacrylate, and 2,2′-azobisisobutyronitrile and characterized by IR and DSC both prior to and after removing the Fe-morin complex by leaching with HCl. The effect of different parameters, such as pH, adsorption and desorption time, type and minimum amount of eluent for removing the complex from polymer was evaluated and optimized. The proposed method is characterized by the detection limit of 3.1 µg l^?1 anddynamic linear range of 25 to 200 µg l^?1, with the relative standard deviation less than 8.8%. The method was applied to the recovery and determination of iron ions in a few real samples.     

Paliperidone-Loaded Self-Emulsifying Drug Delivery Systems (SEDDS) for Improved Oral Delivery

The present research is aimed to improve the oral delivery of paliperidone by loading into self-emulsifying drug delivery systems (SEDDS). Oleic acid, Tween 80, and capmul MCM L8 were selected as oil, surfactant, and co-surfactant, respectively and phase diagram was constructed and the region was identified for the formation of SEDDS. The stable formulations were analyzed for globule size, robustness to dilution and in vitro drug release. The globule size of all the formulations was found to be in the range of 205 to 310 nm with good size uniformity and seems to be dependent on the proportion of oil in SEEDS formulation. The optimized formulation (F3) has been adsorbed onto neusilin and characterized. The DSC and XRD spectra unravel the presence of molecular state of paliperidone in solid SEDDS. The in vitro dissolution study indicates improved dissolution characteristics with higher dissolution efficiency for solid SEDDS (SEDDS-N) compared to pure drug. Further ex vivo permeation studies carried out using rat intestine suggest a 2- to 3-fold improvement in permeation for SEDDS compared to pure drug. In conclusion, SEDDS prove to be potential carriers for improved oral delivery of paliperidone.     

One Model,Two Enzymes: Activation of Hydrogen and Carbon Monoxide

The ability to catalyze the oxidation of both H₂ and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H₂ supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H₂ and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H₂, CO, and H₂/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.     

One Model,Two Enzymes: Activation of Hydrogen and Carbon Monoxide

The ability to catalyze the oxidation of both H₂ and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H₂ supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H₂ and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H₂, CO, and H₂/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles.