pH Region Research Articles

Development of advanced sanitary materials with the use of probiotic paste

Cotton sanitary towels were functionalized by probiotic paste with incorporated Lactobacillus L. fermentum LN99, L. rhamnosus LN113, and L. gasseri LN40 in order to reduce the possibility of infection or inflammation during menstruation and to develop a friendlier product. These towels were characterized through elemental composition using attenuated total reflectance Fourier transform infrared spectroscopy, determination of the pH of aqueous extract, water retention, capillary properties, determination of absorption capacity, and microbiological testing, to assess the antimicrobials’ function and stability of lactic bacteria paste as a coating for sanitary towels. The results of the used methods show that the physical–mechanical properties of towels functionalized by probiotic paste are not significantly different if compared to non-treated ones. Attenuated total reflectance Fourier transform infrared spectroscopy set the successful functionalization of sanitary towels with probiotic paste due to the occurrence of typical probiotics paste peaks. The pH of the probiotic-functionalized sanitary towels was reduced in comparison to the reference material to an acidified region of pH = 5.6, which is an ideal environment for maintaining physiological pH. The decrease in water retention of towels after functionalization is relatively low (8.48 %). The sorption behavior of towels was worse by up to 15% regardless of the reference material, which is still acceptable from a practical point of view and internal standards of the included company Tosama d.o.o. The probiotic-functionalized sanitary towels absorb synthetic blood faster than the reference ones, due to compatibility of the paste with synthetic blood. Moreover, towels obtain functionalities such as good condition for lactobacilli growth with simultaneous pH adjusting, as well as introducing of Staphylococcus aureus reduction. Functionalization of sanitary towels with probiotic paste showed a commercial potential to reduce the probability of infection during the menstruation cycle, as well as being a more customer-friendly product.

Modelling of pH-dependence to develop a strategy for stabilising mAbs at acidic steps in production

Engineered proteins are increasingly being required to function or pass through environmental stresses for which the underlying protein has not evolved. A major example in health are antibody therapeutics, where a low pH step is used for purification and viral inactivation. In order to develop a computational model for analysis of pH-stability, predictions are compared with experimental data for the relative pH-sensitivities of antibody domains. The model is then applied to proteases that have evolved to be functional in an acid environment, showing a clear signature for low pH-dependence of stability in the neutral to acidic pH region, largely through reduction of salt-bridges. Interestingly, an extensively acidic protein surface can maintain contribution to structural stabilisation at acidic pH through replacement of basic sidechains with polar, hydrogen-bonding groups. These observations form a design principle for engineering acid-stable proteins.

Effect of Urea Fertilizer on the Biochemical Characteristics of Soil

Urea-potash mixture was added to the manured soil at three different concentrations equivalent to 0.8, 1.6 and 2.4g f urea per 10Kg of soil. Nitrate and nitrite N concentration in the soil increased within 24h after addition of urea. The nitrate N content in soil without urea was 17 µg and in urea fertilized soils, it ranged from 39.9-47 µg/g of soil after 19h. . Increase in total mineralizable N was around 67- 160% in urea fertilized soils in comparison to the control. Percent conversion of urea to nitrate and nitrite N decreased at higher concentrations of the fertilizer. Addition of biochar to urea amended soil did not bring about significant change in the available N content. Decrease in total mineralizable N and accumalation of available P was observed over the period of 15 days. Addition of urea resulted in acidification of the soil. Acidification of the soil could be correlated with increase in acid phosphatase concentration. The soil amended with biochar exhibited significant buffering capacity in the region of pH 7.4-9.
 Int. J. Appl. Sci. Biotechnol. Vol 7(4): 414-420

UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

The spectral behavior of some p-nitro-p-substituted benzoylhydrazones in the perchloric acid media was followed, applying the UV spectroscopy. The position of the absorption maximum in the spectra was defined in acidic media and the electronic transitions were discussed, as well (7<pH<1). The equilibrium between neutral and protonated form was investigated in the ethanol-water (V/V, 1:1) solutions. The observed changes in the UV spectra suggested that protonation process took place in one step. The pH region of protonation ranges between 1.4 and 2.9. Using the changes in the UV spectra which appear as a result of the protonation reaction the stoichiometric dissociation constants were determined numerically (pKBH+ = n·pH + logI) and graphically (intercept of the dependence of logI on pH). Thermodynamic dissociation constants were estimated as an intercept of dependence of pKBH+ on square root of the ionic strength. In order to achieve that, measurements were performed at different ionic strengths: 0.1, 0.25 and 0.5 mol/dm3, adjusted with sodium perchlorate. The obtained thermodynamic pKBH+ values ranged between 2.07 and 2.58. In order to predict proton transfer at a given pH, semiempirical methods AM1 and PM3 were applied. The influence of the substituents present in the p-position of the benzene ring on pKBH+ values of investigated hydrazones was discussed, too. Total energy, binding energy, enthalpy of formation, Gibbs energies of formation, atomic charge and proton affinity values were used to predict protonation site in hydrazone molecule. Furthermore, the stability and the proton affinity of the isomers (E and Z) in which hydrazones exist and their protonated forms were defined.

Thermo-Sensitivity of poly-N-isopropylacrylamide with Statistically Introduced D,L-Allylglycine Betainic Units

Statistical copolymers of N-isopropylacrylamide containing 2.2 – 2.7 mol % D,L-allylglycine were synthesized. The sample with 2.2 mol % allylglycine and molar mass 320000 g/mol was studied using light scattering and turbidimetry while heated in water and water–salt solutions. Temperature dependencies of light scattering intensity and optical transmission as well as hydrodynamic size and composition of the scattering entities were obtained in a wide range of pH. The onset temperatures of phase separation were independent of pH; however, in the basic pH region the phase transition was widened as compared to the neutral and acid media. It was shown that a small content of allylglycine results in a different thermoresponsive behavior of the copolymer as compared with N-isopropylacrylamide homopolymer. The addition of a physiological amount of NaCl shifts the copolymer thermo-sensitivity toward lower temperatures.

The Effect of Solution pH on the Oxidation of Sulfite Ions and the Formation of Oxides on the Gold Electrode

The results of studying the effect of solution pH on the electrode process that occurs on the gold electrode in solutions of sodium sulfite, sulfuric acid, and alkali, and also in the universal buffer of Britton–Robinson (pH 2–14) are shown. In sodium sulfite solutions, this electrode process represents a combination of the oxidation of sulfite species and the formation of oxides on the gold surface that proceeds simultaneously in the same potential region. It is shown that the solution pH and the oxidation of sulfite species have no effect on the amount of gold α-oxide formed. At the same time, the solution pH has a strong effect on the oxidation of sulfite species. Thus, the voltammograms measured in solutions with pH approximately between 2 and 11 are identical, i.e., the process rate is independent of the solution acidity and its partial composition. These results suggest that in this pH region, the oxidation of sulfite ions can be interpreted by the overall reaction $$2{\text{SO}}_{3}^{{2 - }} \to {{{\text{S}}}_{{\text{2}}}}{\text{O}}_{6}^{{2 - }} + 2{\text{e}}$$ to produce dithionate ions. In strongly alkaline solutions (pH 12.5–14), the oxidation potential shifts in the negative direction and the current decreases with increasing pH. These results suggest that in strongly alkaline solutions, the oxidation of sulfite ions can proceed on the partly blocked electrode surface by the reaction $${\text{SO}}_{3}^{{2 - }} + 2{\text{O}}{{{\text{H}}}^{ - }} \to {\text{SO}}_{4}^{{2 - }} + {{{\text{H}}}_{{\text{2}}}}{\text{O}} + 2{\text{e}}$$ to form sulfate ions. The changeover of the mechanism of oxidation of sulfite ions takes place in a narrow potential region in solutions with pH from 11 to 12.5 and is accompanied by anomalously sharp changes in the measured current. The latter anomalies are associated with the peculiar dynamics of the process of passivation/depassivation of the electrode surface by gold oxides.

Selective Extraction of Light Lanthanides(III) by N,N-Di(2-ethylhexyl)-diglycolamic Acid: A Comparative Study with N,N-Dimethyl-diglycolamic Acid as a Chelator in Aqueous Solutions.

The complexation and selectivity of N,N-di(2-ethylhexyl)-diglycolamic acid (HDEHDGA/kerosene, HA) toward the light lanthanides, La(III), Ce(III), Pr(III), and Nd(III), are presented for the extraction from chloride media. In the low pH region (pH 1.8–2.8), the obtained data reveal that the extraction of Ln(III) is governed by cation-exchange mechanism and is driven by the negative change in enthalpy. The results from the slope analysis method suggest the formation of LnA3·(HA)1or2 in the extraction process. As major extracted species with a core of LnA3 in the first coordination sphere, LnA3 might connect with one or two additional HA molecules in the second coordination sphere by hydrogen bonding. The LnA3 core might share similar coordination geometry to those of 1:3 Ln(III) complexes (LnA′3) with water-soluble N,N-dimethyl-diglycolamic acid (HDMDGA, HA′) formed in aqueous solutions or in solid-state compounds. The correlation between the extraction with HDEHDGA (HA) as an extractant and the complexation with HDMDGA (HA′) as a chelator has been explored by interpreting the separation factors for HA with the difference in the stability constants for HA′. Consequently, the ratios of the stability constants of the corresponding 1:3 complexes (LnA′3) with HDMDGA could be reasonably translated to the separation factors (SFs) with HDEHDGA, providing a valuable approach for understanding the origin of the extraction/separation mechanism. By comparing the extraction selectivity of HDEHDGA with that of the currently deployed extractants in the industry such as P204, P507, and Cyanex 272, HDEHDGA offers outstanding selectivity with considerable SFs (SFCe/La = 6.68, SFPr/Ce = 2.79, and SFNd/Pr = 2.65) for light Ln(III) pairs under conditions of low acid concentrations.

The role of fluoroaluminate complexes on the adsorption of fluoride onto hydrous alumina in aqueous solutions

Activated alumina (AA) has been extensively applied in the defluorination of industrial wastewaters and groundwater. Although the dissolution of AA due to formation of fluoroaluminate complexes (AlFx3−x), especially in acidic condition, has been observed, its role on fluoride uptake by alumina has not been discussed in any previous literature, most of which consider F− as the sole adsorbed species. The present study described the effect of fluoroaluminate complexes on fluoride adsorption onto alumina. Results indicated that fluoroaluminate complexes, major fluoride species at pH < 6, were responsible for total fluoride adsorbed. Free fluoride ions were adsorbed mainly in the alkaline pH region, e.g., pH > 6. The dissolution of AA during defluorination was measured and analyzed by the thermodynamic solubility model. The surface concentration of F− and AlFx3−x were calculated considering electrostatic interactions. Characterization of fluoride-laden AA by XPS revealed that the fraction of surface Al-F species decreased with pH, which suggested the transition of the surface fluorinated species to that of free fluoride ions. The stability constants of four surface complexes, namely, AlOH-FAl2+, AlOH-F2Al+, AlOH2+-F− and AlOH-F−, were 106.88, 105.36, 102.72 and 102.36, respectively. Obviously fluoroaluminate complexes exhibited stronger chemical bonds with the surface hydroxy species than free fluoride.

Influence of solution acidity on growth kinetics, structure and magnetic properties of Co-P films, obtained by chemical deposition

The results of studies of the effect of solution acidity on the growth kinetics, structure and magnetic properties of Co-P films obtained by chemical deposition are presented. It was shown that the growth of Co-P films in the low pH region occurs mainly due to the growth of crystallite sizes, and in the high pH region, due to an increase in the nucleation rate. From the analysis of the chemical equilibrium of redox reactions, taking into account the balance of citrate and hydroxyl complexes of Co, a qualitative explanation of the features of the change in the rate and nature of the deposition of Co atoms from pH is proposed.

Гидрохимический синтез пленок халькогенидов металлов. Часть 42. Экспериментальная проверка областей осаждения PbSe селеносульфатом натрия и селеномочевиной в присутствии различных лигандов

Calculation of ionic equilibria in the reaction system for synthesis of PbSe thin films was carried out. Three reaction systems containing the following combinations of reagents were considered: sodium citrate with liquid ammonia and sodium selenosulfate (system 1) or selenourea (system 2) used as chalcogenizer, ethilendiamine, sodium acetate and selenourea (system 3).The main lead complex compoundsprevented the fast PbSe formation in system 1 and 2 in region of pH of intensive selenosulfate and selenourea decomposition were hydroxo-citrate complexes. In the system 3 complexes with ethilendiamine and acetate-ions played the most significant role. For evaluating the deposition conditions of the main and impurity phases (metal hydroxides and cyanamides) by thermodynamic calculations taking into account the sizes of critical nucleis, the boundary conditions and regions of formation of PbSe, Pb(OH)2, PbCN2 in the studied reaction systems were found. The calculation results are presented in the form of three-dimensional dependencies in the coordinates “indicator of the initial concentration of the metal salt – pH of the solution – ligand concentration” and “indicator of the initial concentration of the metal salt – pH of the solution – concentration of the chalcogenizer”. Based on the calculations and preliminary experiments, the compositions of the discussed reaction mixtures were formed for the chemical bath deposition of PbSe films, which, in addition to the main components, included a dopant in the form of ammonium iodide. In the synthesis process at a temperature of 353 K (system 1 and 2) for 60 minutes and 308 K for 90 minutes (system 3), using all the studied reaction systems on glass substrates, homogeneous PbSe layers with a thickness of ~500 to ~700 nm were obtained. The ratio between the main elements of Pb and Se in the film varies between 0.98-1.32, and the iodine content is 7-11 at.% depending on the composition of the reaction bath.

A fluorescence "turn-on" sensor for detecting hydrazine in environment

Hydrazine (N2H4) has been classified as an environmental contaminant and human carcinogen owing to its high toxicity. Being exposed to high levels of hydrazine can cause irreversible damage to human bodies. Hence, it is significant to explore an effective method to selectively recognize and detect it. In this work, a new “turn-on” fluorescence probe, coumarin-thiophene (C-T), was designed based on PET (photo-induced electron transfer) mechanism by employing 5-chlorothiophene-2-carbonyl chloride as a electron donor and coumarin as a electron acceptor. The flourescence could be recovered due to the interruption of PET by stripping the 5-chlorothiophene-2-carbonyl chloride when treated with hydrazine. The mechanism was further verified through 1H NMR titration and spectral analysis. Additionally, The probe exhibited a high selectivity towards hydrazine over other common ions and amine-containing species with a distinct fluorescence enhancement at 450 nm. The probe could operate over a wide pH region (4–10) with a detection limit as low as 0.0047 μM (1.5 ppb). Furthermore, it could selectively detect hydrazine in different water samples which indicated its potential for practical applications.

Electrochemically mediated calcium phosphate precipitation from phosphonates: Implications on phosphorus recovery from non-orthophosphate

Phosphonates are an important type of phosphorus-containing compounds and have possible eutrophication potential. Therefore, the removal of phosphonates from waste streams is as important as orthophosphate. Herein, we achieved simultaneously removal and recovery of phosphorus from nitrilotris (methylene phosphonic acid) (NTMP) using an electrochemical cell. It was found that the C–N and C–P bonds of NTMP were cleaved at the anode, leading to the formation of orthophosphate and formic acid. Meanwhile, the converted orthophosphate reacted with coexisting calcium ions and precipitated on the cathode as recoverable calcium phosphate solids, due to an electrochemically induced high pH region near the cathode. Electrochemical removal of NTMP (30 mg/L) was more efficient when dosed to effluent of a wastewater treatment plant (89% in 24 h) than dosed to synthetic solutions of 1.0 mM Ca and 50 mM Na2SO4 (43% in 168 h) while applying a current density of 28 A/m2 and using a Pt anode and Ti cathode. The higher removal efficiency of NTMP in real waste water is due to the presence of chloride ions, which resulted in anodic formation of chlorine. This study establishes a one-step approach for simultaneously phosphorus removal and recovery of calcium phosphate from non-orthophosphates.

Actinide and Lanthanide Adsorption onto Hierarchically Porous Carbons Beads: A High Surface Affinity for Pu.

Structured carbon adsorbents were prepared by carbonizing macroporous polyacrylonitrile beads whose pores were lined with a mesoporous phenolic resin. After activation, the beads were tested for minor actinide (Np and Am), major actinide (Pu and U) and lanthanide (Gd) adsorption in varying acidic media. The activation of the carbon with ammonium persulfate increased the surface adsorption of the actinides, while decreasing lanthanide adsorption. These beads had a pH region where Pu could be selectively extracted. Pu is one of the longest lived, abundant and most radiotoxic components of spent nuclear fuel and thus, there is an urgent need to increase its security of storage. As carbon has a low neutron absorption cross-section, these beads present an affordable, efficient and safe means for Pu separation from nuclear waste.

CO2 Leakage Behaviors in Typical Caprock-Aquifer System during Geological Storage Process.

In this study, a 3D reactive flow simulation model is built to simulate the leakage processes though assumed leakage channels. The geochemical reactions are coupled with fluid flow simulation in this model with consideration of reservoir minerals calcite, kaolinite, and anorthite. As an essential trigger for geochemical reactions, changes in pH value are investigated during and after the CO2 injection process. By comparing CO2 migration with/without geochemical reactions, the influence of geochemical processes on CO2 leakage is illustrated. The leakage behaviors through leakage channels with different permeabilities are evaluated. Influence of reservoir temperature on CO2 leakage is also exhibited. Furthermore, the effects of the distance between the injection well and leakage zone on the leakage potential are studied. The results indicate that the geochemical reactions have impact on the leakage processes, which can decrease the leakage level with the presence of geochemical reactions. The region of low pH enlarges with continuous injection of CO2. Hence, monitoring changes in pH can reflect the migration of CO2, which can provide an alert for CO2 leakage. The occurrence of the leakage phenomenon is postponed with increasing the distance between the CO2 injection well and the leakage channel. However, the leakage level tends to be consistent with injecting more CO2. The CO2 leakage risk can be reduced through the leakage channels with lower permeability. With the presence of higher reservoir temperatures, the leakage risk can be improved. These results can provide references for the application of monitoring methods and prediction of CO2 front associated with geochemical processes.

Development of Copper Cobalt Sulfide with Cu : Co Ratio Variation on Carbon Cloth as an Efficient Electrode Material for the Oxygen Evolution Reaction

AbstractWhen designing a device for energy conversion, development of a highly active catalyst for OER (oxygen evolution reaction) reaction in alkaline medium is of utmost importance. For energy conversion, herein, we developed copper cobalt sulfide on carbon cloth (CC) using a simple and facile hydrothermal method. A vertically grown 2D sheet‐like structure of copper‐cobalt sulfide is observed using L‐cysteine as a sulfur source. An optimized ratio of copper(II) and cobalt(III) and the best sulfur source are found to boost the electrocatalytic activity of mixed metal thiospinel for OER. Several characterization techniques (XRD, Raman, FESEM, TEM, XPS, and ICP‐AES) were used to confirm phase purity, morphology, and composition of copper cobalt sulfides. We have established that 2D nanosheets of CuCo3Sz/CC exhibited superior electrocatalytic performance over bare RuO2 in 1.0 M KOH solution. It is observed that CuCo3Sz/CC need only 105 mV overpotential to generate 5 mA/cm2 current density. CuCo3Sz/CC is very stable and able to produce unaltered current density under an applied potential of 1.615 V vs. RHE for 48 h. Electrochemically active surface area calculation is performed for all catalysts to confirm higher electrocatalytic activity. The catalyst, CuCo3Sz/CC is used in a broad pH region using 0.5 M KOH, saline water, and 0.5 M Na2SO4 electrolyte solution to widen the applicability of water splitting. This work shows an avenue to develop active and durable electrocatalyst for OER without using any noble metal electrocatalyst.

Conformational Stability Effect of Polymeric Iron Chelators.

SummaryThe design and synthesis of metal chelators with extraordinary metal affinities is a basic and challenging scientific problem of both fundamental and practical importance. Here, we demonstrate a “conformational stability effect” that can significantly enhance the metal affinity of ligands after conjugation to polymer chains with the ability to spontaneously adopt a specific conformation as an optimal “soft” scaffold to ensure maximum thermodynamic stability of the metal complexes. Using iron chelators as models, we show that simple conjugation of small molecule catechol ligands to a polyallylamine chain resulted in more than 8–9 orders of magnitude enhancement of the iron-binding affinity, which is comparable to that of enterobactin, the strongest iron chelator ever known. This study demonstrates that flexible polymer chelators may realize the highest possible metal affinities of the conjugated ligands owing to their ability to achieve an optimal conformation, which could advance the identification of strong metal chelators.

Oxidative DNA Cleavage, Formation of μ-1,1-Hydroperoxo Species, and Cytotoxicity of Dicopper(II) Complex Supported by a p-Cresol-Derived Amide-Tether Ligand.

Metal complexes to promote oxidative DNA cleavage by H2O2 are desirable as anticancer drugs. A dicopper(II) complex of known p-cresol-derived methylene-tether ligand Hbcc [Cu2(bcc)]3+ did not promote DNA cleavage by H2O2. Here, we synthesized a new p-cresol-derived amide-tether one, 2,6-bis(1,4,7,10-tetrazacyclododecyl-1-carboxyamide)-p-cresol (Hbcamide). A dicopper(II) complex of the new ligand [Cu2(μ-OH)(bcamide)]2+ was structurally characterized. This complex promoted the oxidative cleavage of supercoiled plasmid pUC19 DNA (Form I) with H2O2 at pH 6.0-8.2 to give Forms II and III. The reaction was largely accelerated in a high pH region. A μ-1,1-hydroperoxo species was formed as the active species and spectroscopically identified. The amide-tether complex is more effective in cytotoxicity against HeLa cells than the methylene-tether one.

Quinoline based chromogenic and fluorescence chemosensor for pH: Effect of isomer

Abstract We report here the synthesis, characterization and pH sensing properties of a Schiff-base molecule, 2-hydroxy-5-methyl-3-((quinolin-2-ylimino)methyl)benzaldehyde (HL-2-qui) to compare the results observed for its isomers having different position of imino linkage on the quinoline unit. Fluorescence intensity of HL-2-qui at 530 nm enhanced gradually with the increase in pH of the media whereas its isomers showed ratiometric pH sensing behavior under similar conditions. HL-2-qui was colorless in acidic condition and yellow in alkaline medium under visible light while under UV light, the colors of the probe changed to indigo and fluorescent green, respectively. The chemosensor was applied in the detection of different pH regions using lemon juice and river water as the real sample.

PH dependence of the chirality of nematic cellulose nanocrystals

Cellulose nanocrystals produced by acid hydrolysis of native cellulose form a well-known chiral nematic liquid crystal phase. The mechanism involved in the formation of chirality has been the subject of a vigorous discussion. The pH and concentration dependence of the phase is studied using cellulose nanocrystal droplets within a silicon oil suspension, which allows for convenient real-time microscale manipulation of phase behaviors and properties. We demonstrate the existence of nematic phases at both low and high pH regions consistent with the Stroobants - Lekkerkerker - Odijk theory. Our results confirm electrostatic interactions play a critical role in controlling the strength of the chirality.

PH Behavior of Polymer Complexes between Poly(carboxylic acids) and Poly(acrylamide derivatives) Using a Fluorescence Label Technique.

In order to clarify the local environment during interpolymer complex formation between poly(carboxylic acids) and poly(acrylamide derivatives) with different N-substitutions, a fluorescence label technique was used. 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) was used as an intramolecular fluorescence probe. All polymers were synthesized by free radical polymerization. Interpolymer complexation was monitored by charge transfer emission from the VDP unit. Both of the poly(carboxylic acids) formed interpolymer complexes with poly(N,N-dimethylacrylamide) (polyDMAM). The micro-environments around the VDP unit in the acidic pH region for the poly(methacrylic acid) (polyMAAc) and polyDMAM mixed systems were more hydrophobic than those of the poly(acrylic acid) (polyAAc) and polyDMAM mixed systems, as the α-methyl group of the MAAc unit contributed to hydrophobicity around the polymer chain during hydrogen bond formation. This suggests that, when the poly(carboxylic acids) and poly(acrylamide derivatives) were mixed, with a subsequent decrease in the solution pH, a hydrogen bond was partially formed, following which the hydrophobicity of the micro-environment around the polymer chains was changed, resulting in the formation of interpolymer complexes. Moreover, the electron-donating ability of the carbonyl group in the poly(acrylamide derivatives) had an effect on complexation with poly(carboxylic acids).