Effect Of pH Variation Research Articles

Effect of pH variation on flexural and compressive properties of composite resins

구강내의 pH는 다양한 음식과 음료수에 의해 폭넓은 변화의 폭을 가진다. 본 연구는 pH가 복합레진의 굴곡 및 압축성질에 미치는 영향을 평가한 것이다. 이를 위하여 4종의 복합레진을 시료로 선택하였고, 시료를 광조사한 후 pH가 각각 3, 7.1, 9인 용액에 실온에서 2주 동안 담가두었다. 그리고 만능시험기를 이용하여 굴곡 및 압축성질을 평가하였다. 그 결과 pH에 상관없이 시료는 용액에 담긴 후에 초기 굴곡 및 압축강도가 각각 1.5-30.0%와 0.3-19.6%로 유의하게 변하였고 modulus도 각각 4.4-29.0%와 3.5-21.5%로 유의하게 변했다. 그러나 각기 다른 pH 조건에 대해서 값의 변화는 일관성과 유의성이 없었다.

An efficient calixarene-based functional material for the sorption and recovery of Cr(VI) from water

ABSTRACTThe present study elaborates synthesis of calix[4]arene-functionalised resin (GX) and its application in sorption of Cr(VI) from water. Effect of variation in pH was explored through batch study, which indicates that maximum sorption of 89% occurs at pH 4. Similarly, in dynamic mode, various parameters, i.e. change in concentration, flow rate and bed height, were optimised using Bed Depth Service Time (BDST) model. Based on the BDST model, maximum sorption capacity was found to be 85 mg g−1 at optimum conditions. The (GX) is recoverable up to 97% and also has the potential to regenerate and reuse till six cycles.

Influence of pH Modification on Catalytic Activities of Metal-Doped IrO2 Nanoparticles

The effects of pH variation on the catalytic activity of IrO2 nanoparticles (NPs) doped with Cr (an early transition metal) or Ni (a late transition metal) depending on the amount of defect structures on the NP surfaces were analyzed. It was found that both Cr@IrO2 and Ni@IrO2 NPs, fabricated under basic conditions (pH = 13.5) denoted as Cr@IrO2-B and Ni@IrO2-B, respectively, were the best catalysts among the eight tested ones. Moreover, it was confirmed that variation in pH resulted in the changes in the surface area (defect structure), which were considered to be responsible for the changes in the catalytic properties of these NPs. For the oxygen evolution reaction, these NPs exhibited relatively smaller overpotential (η) values than other tested Cr@IrO2- and Ni@IrO2-containing NPs. Furthermore, methylene blue degradation analysis and OH radical formation experiments by benzoic acid showed the same trend. Thus, we confirmed that the catalytic activity of transition metals doped IrO2 NPs fabricated under basic conditions can be improved.

Effect of pH variations on morphological transformation of biosynthesized MgO nanoparticles

Plant leaf extract synthesis of nanoparticles serves as a better alternative to chemical synthesis routes as the nanoparticles synthesized are less toxic and possess higher flexibility for scaling up process. Phyto-synthesized metal oxides, especially magnesium oxide (MgO) nanoparticles possess enormous unique properties to be used in drug delivery and therapeutic application. Thus, the aim of the present work is to investigate the effect of pH on the shape transformation of MgO nanoparticles prepared using Amaranthus tricolor leaf extract. UV-visible spectrophotometer and dynamic light scattering technique were initially used to analyze the effect of pH variation on particle sizes and surface charges. MgO nanoparticles at pH 3 were identified to be formed in smaller sizes of ∼44nm with a slightly negative surface charge of −3.39 mV and were postulated that its shape can be transformed to hexagon. Hexagonal shaped particles are highly beneficial in biomedical application as they show less cytotoxicity and increased bioactivity due to the presence of edge surface atoms. FTIR spectral analysis and TEM images confirm that the size and shape of the MgO nanoparticle at acidic pH 3 was reduced and transformed to hexagon. Additionally, possible mechanism of nanoparticle protonation and deprotonation leading to their morphology changes was also proposed in the paper.

Investigating the influence of pH and selected heating media on thermal destruction kinetics of Geobacillus stearothermophilus (ATCC10149)

Geobacillus stearothermophilus is a thermophilic spore-forming bacterium which is used for intense thermal process validations (10 min–15 min). Several factors including the pH and heating medium influence the heat resistance of such microbial spores. In this study, the influence of using different buffer types including McIlvaine and phosphate was compared to distilled water at pH 7. Also, the effect of pH variations was studied using McIlvaine buffer at pH 3, 4, 5, 6, 7, and 8. All kinetics studies were conducted at 110 to 120 (°C). Results showed higher heat sensitivity (higher Z value) in distilled water (8.27 °C) than in phosphate (9.21 °C) and McIlvaine buffers (9.59 °C); likely being influenced by the high percentage of inorganic salts present in these buffers. The spores had the highest heat resistance at neutral pH, and the associated D values decreased both below and above pH 7.0. The pH effect on enhancing the heat sensitivity was higher at 110 °C, but the overall temperature influence was not significantly different (p > 0.05). Further, both first-order and Weibull models were compared for thermal destruction kinetics of G. stearothermophilus. Results demonstrated some concavity in the log-linear survival curves suggesting a slightly better fit for the Weibull model in some cases, but the model did not show any better prediction than the first-order model for a 3D lethality (Fo) value of 15 min. The combined effect of pH and temperature also showed cubic trends, and the Ea ranged between 240 and 398 (kJ) at pH 4–7.

Fixed‐Bed and Batch Adsorption of Pharmaceuticals from Aqueous Solutions on Ionic Liquid‐Modified Montmorillonite

AbstractBatch and column adsorption of four pharmaceuticals, namely, tetracycline (TC), sulfamethoxazole (SMZ), nalidixic acid (NAD), and chloramphenicol (CHL) on ionic liquid modified montmorillonite (Mt‐IL) was evaluated. The effects of variation in pH and contact time were analyzed and the data were fitted to kinetics and isotherm models. The equilibrium experimental data were best explained by the Freundlich model. A pseudo second‐order kinetic model described all pharmaceuticals adsorbed on Mt‐IL. In column studies, the exchange zone depth, adsorption capacity, the required time for the pharmaceuticals to move through the height of the adsorbent in the column, and adsorption rates were investigated by the Yoon‐Nelson and the Thomas and Adams‐Bohart models.

Thin Layer Chromatographic Resolution of Some β-adrenolytics and a β2-Agonist Using Bovine Serum Albumin as Chiral Additive in Stationary Phase

Direct enantiomeric resolution of commonly used five racemic β-adrenolytics, namely, bisoprolol, atenolol, propranolol, salbutamol and carvedilol has been achieved by thin layer chromatography using bovine serum albumin (BSA) as chiral additive in stationary phase. Successful resolution of the enantiomers of all racemic β-adrenolytics was achieved by use of different composition of simple organic solvents having no buffer or inorganic ions. The effect of variation in pH, temperature, amount of BSA as the additive, and composition of mobile phase on resolution was systematically studied. Spots were visualized in iodine vapors. Native enantiomers for each of the five analytes were isolated and identified and their elution order was determined. The limit of detection was found to be 0.7, 1.2, 0.84, 1.6 and 0.9 μg (per spot) for each enantiomer of bisoprolol, atenolol, propranolol, salbutamol and carvedilol, respectively.

ECOLOGICAL ENGINEERING OF MICROALGAE FOR ENHANCED ENERGY PRODUCTION

Microalgae are considered as potential source of renewable energy generation. Algal biomass is used as key feedstock for renewable energy generation using algal resources. Accumulation of biomass mostly depends on the growth rate, which is usually regulated by pH and salinity. Present study was conducted to study the effect of variation in pH and saline rangeson growth, biomass and lipid content of a freshwater microalga Chlorella vulgaris. The growth, biomass and lipid content showed a significantdifference due to the variation in pH and saline range. The growth and lipid content was maximum at pH 7.0 with compared to 6, 8 and 9. On the other hand an increase of salinity from 0.1M to 0.25 M caused decreased growth rate, whereas the lipid content showed an increasing trend.

Influence of pH on particle size, band-gap and activation energy of CdS nanoparticles synthesized at constant frequency ultrasonic wave irradiation

Cadmium sulfide (CdS) nanoparticles are prepared through different potential of hydrogen (pH) ranging from 8 to 12 at constant frequency ultrasonic wave irradiation. Sodium hydroxide (NaOH) was preferred as the pH modifier. The effect of pH variation on the structural, optical and electrical properties of CdS particles was studied. The particle sizes from X-Ray diffraction (XRD) analysis were found in the range 29–39nm. The results of the optical absorption showed that the band gap energy values of the CdS nanoparticles decreased from 2.48 to 2.38eV with increasing pH values which was measured in diffused reflectance spectra (DRS). Photoluminescence spectra were recorded to investigate the presence of electronic transitions as well as interstitial position of cadmium. A High Resolution Scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) study revealed the particle size and morphology of the mixed spherical shaped and rod shaped nanoparticles. Electrical conductivity measurements were carried out on CdS nanoparticles and the Activation energy of the samples were calculated by dc conductivity studies.

Effect of pH variation on the stability and structural properties of In(OH)3 nanoparticles synthesized by co-precipitation method

Indium hydroxide (In(OH)3) nanoparticles were synthesized at various pH values (8–11) by co-precipitation method. Its properties were characterized by X-ray diffractometer, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscope. The electrostatic stability of nanoparticles is carried out through zeta potential measurement. The crystallite size of nanoparticles calculated by Scherrer equation has similar trend with the values obtained from William–Hall plot. TEM images show that the particles size is within the range of 11.76–20.76 nm. The maximum zeta potential is 3.68 mV associated with the smallest particle size distribution of 92.6 nm occurred at pH 10. Our work clearly confirms the crystallite size, stability and the morphology of In(OH)3 NPs are strongly depending on the pH of precursor solution.

Effects of pH variations on anodic marine consortia in a dual chamber microbial fuel cell

The effect of anodic pH on Microbial fuel cells (MFCs) inoculated with marine consortia was investigated to characterize the microbial community adaptation to possible pH environmental changes and to define the pH extreme boundaries beyond which MFCs do not run properly.Tests were conducted in triplicate using different feeding pH values (pHfeed) ranging from 3 to 13. The MFCs inoculated with marine consortia had a strong self-regulation ability and actively counterbalanced small variations in pHfeed maintaining the pH inside the anodic chamber (pHanode) close to neutrality.As soon as the pHanode deviated from neutrality it affected MFCs' performances. Alkaline conditions with pHanode values between 8 and 10 corresponded to the formation of a denser biofilm together with the best performance in terms of maximum power density (Pmax). Conversely, when the pHanode reached values lower than 5.5 or higher than 10, a sharp drop in MFC performances, as well as a decrease of viable population, were observed. Interestingly, the system was able to survive these extreme conditions and restart working effectively when neutrality was reset.The obtained results underline the high adaptability and recovery ability of anodic marine consortia even in extreme conditions, suggesting the employment of this inoculum for MFC applications as biosensors for on-site seawater monitoring or as power supply units to be installed in remote area.

Molecular forces study and microstructure and gelling properties of smooth hound protein gels prepared by heat-induced gelation process: Effect of pH variation on textural and functional properties

Smooth hound gels (SHGs) were prepared from the viscera by heat treatment at different pH values (2.0, 5.0, 7.0 and 9.0). Their physicochemical and functional properties, microstructure and molecular forces were investigated. The pH variation was found to influence the protein molecular weight distribution resulting in different gelling properties. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profiles, SHG-9 prepared at pH 9.0 contained the greatest amount of high molecular weight proteins. Further, the SHG-9 exhibited the highest gel strength, fracture resistance and elasticity. On the contrary, microstructure and infrared spectra analyses showed that acidic conditions provided gel networks with unarranged secondary structure and a high hydration level, which might be attributed to the formation of hydrogen bonds between polymer molecules. In addition, the molecular forces study showed that the primary dominated intermolecular forces involved in the SHGs were hydrophobic interactions and hydrogen bonds, while the secondary forces included electrostatic interactions and disulfide bridges. These results were confirmed by the levels of free amino acids. Thus, this study identified opportunities to develop high value-added products from fish by-products that might be used to carry out the function of the desired food application.

Arsenate removal from sulphate-containing water streams by an ion-exchange membrane process

Abstract A possible limitation of applying Donnan dialysis for arsenate removal from drinking water supplies is when sulphate is present as an accompanying anion in the water to be treated, due to strong competition between arsenate and sulphate transport through standard grade anion-exchange membranes. This work aims at evaluating the feasibility of employing an ion-exchange membrane Donnan dialysis based process with a new strategy of using sulphate as the driving counter-ion for arsenate counter-transport and removal from sulphate-containing drinking water streams. The process performance with different arsenate receiving solutions (containing chloride or sulphate as driving counter-ions and with or without arsenic precipitation) was investigated and compared. Experiments were carried out to separate arsenate from contaminated water comparing the performance of three anion-exchange membranes: one with mono-valent anion permselective properties and two standard grade membranes. As selection criteria, the transport rate of arsenate and its membrane retention were investigated. The effects of pH variation and co-ion (cation) leakage on the Donnan dialysis process efficiency were also studied. Efficient arsenic removal was achieved through integrating Donnan dialytic transport of arsenate with its simultaneous precipitation in the receiving compartment with FeSO 4 . The process proposed is environmentally friendly and with minimal maintenance requirements, which makes it especially attractive to be applied in rural areas located far from centralized drinking water supply infrastructures.

The Influence of Arginine on the Response of Enamel Matrix Derivative (EMD) Proteins to Thermal Stress: Towards Improving the Stability of EMD-Based Products.

In a current procedure for periodontal tissue regeneration, enamel matrix derivative (EMD), which is the active component, is mixed with a propylene glycol alginate (PGA) gel carrier and applied directly to the periodontal defect. Exposure of EMD to physiological conditions then causes it to precipitate. However, environmental changes during manufacture and storage may result in modifications to the conformation of the EMD proteins, and eventually premature phase separation of the gel and a loss in therapeutic effectiveness. The present work relates to efforts to improve the stability of EMD-based formulations such as Emdogain™ through the incorporation of arginine, a well-known protein stabilizer, but one that to our knowledge has not so far been considered for this purpose. Representative EMD-buffer solutions with and without arginine were analyzed by 3D-dynamic light scattering, UV-Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy at different acidic pH and temperatures, T, in order to simulate the effect of pH variations and thermal stress during manufacture and storage. The results provided evidence that arginine may indeed stabilize EMD against irreversible aggregation with respect to variations in pH and T under these conditions. Moreover, stopped-flow transmittance measurements indicated arginine addition not to suppress precipitation of EMD from either the buffers or the PGA gel carrier when the pH was raised to 7, a fundamental requirement for dental applications.

Outdoor cultures of Chlorella pyrenoidosa in the effluent of anaerobically digested activated sludge: The effects of pH and free ammonia

A freshwater algae Chlorella pyrenoidosa was cultured outdoors using anaerobically digested activated sludge effluent. The effects of pH variations were evaluated. The coupled pH variations and free ammonia toxicity significantly affected the algal growth, lipids accumulation and contamination control during every season. The free ammonia toxicity at high pH levels actually inhibited the algal growth. Compared to an optimal algal growth at a pH of 5.7–6.5, biomass productivity at a high pH of 8.3–8.8 was reduced by 67.15±6.98%, 54.39±6.42% and 83.63±5.71% in the spring, fall and summer, respectively. When the pH rose above 9.1–9.6, algae were unable to grow in the wastewater. However, high pH levels reduced contamination (e.g., bacteria and microalgae grazers) and triggered lipids accumulation in algal cells. These findings suggest that pH control strategies are essential for this type of algal wastewater system, where ammonia is the dominant nitrogen source.

Synthesis, characterization and application of iron-aluminate nodules in advanced Fenton’s oxidation process

Application of sol–gel synthesized, porous, iron doped alumina nodule in Fenton’s oxidation process has proved to be an economical and operational oxidant for destruction of model pollutants like benzene, toluene and xylene (BTX) under batch conditions. The Effect of variation in pH and H2O2 concentration were studied with respect to BTX and COD removal. The results suggest an effective oxidation of aqueous solution of BTX with iron doped alumina nodules and hydrogen peroxide in acidic medium. It was observed that concentration of 1.5g/l of H2O2 with iron doped alumina nodule catalyst (2.29% w/w of iron doped on alumina) at 3.5 pH was optimum for 99% of BTX degradation and 66% of COD removal. Homogeneous mixing of iron with aluminium alkoxides using sol–gel method has proved to be one of the most effective and economical bottom up approach in the synthesis of sintered, porous, iron doped alumina nodules, which appears to be a promising material in Fenton’s oxidation process.

Monitoring Effects of Excipients, Formulation Parameters and Mutations on the High Order Structure of Filgrastim by NMR.

Filgrastim is the generic name for recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF). It is marketed under the brand name Neupogen® by Amgen. Since this product has lost patent protection, many biosimilar versions have been approved or are in the process of filing for market authorization throughout the world. Here we show that NMR spectroscopy can be used to assess the three-dimensional structure of the active ingredient in the formulated approved product Neupogen®. Recombinant metHuG-CSF was prepared in E. coli and isotopically enriched with (13)C and (15) N isotopes. NMR spectroscopy was used to study the effects of excipients on the conformation. The effects of pH variation on the amide chemical shifts suggest the presence of cation-pi interactions between His-79 and Trp-118, and His-156-Trp-58-His-52 that stabilizes the conformation at low pH. This may be associated with a small local conformational change. The NMR data showed that polysorbate does not interact significantly with filgrastim thus allowing the collection of spectra in the presence of 20 times the formulation concentration in the sample. However, at higher detergent concentrations a reduction of signal intensity is observed. Conclusions The NMR fingerprint assay applied to filgrastim (Neupogen® and a CRS from the European Pharmacopeia (EP)) provided residue specific information of the structure of the drug substance. In addition to current methods, the ability to assess the conformation with a high degree of resolution can greatly facilitate comparability exercises.

Synthesis And Characterization Of SiO2, SnO2 And TiO2 Metal Oxide Shells Covering Cu2O Particles

Abstract In this work is described a means of improving the chemical stability of Cu2O@SiO2, Cu2O@SnO2 and Cu2O@TiO2 materials. The SiO2, SnO2 and TiO2 coated samples were stable from pH 3 to pH 10 for up to seven days. To determine the stability of the coated nanoparticles, and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Details of the effect of variations in pH on the phase stability of core-shell type Cu2O were characterized using transmission electron microscopy and X-ray diffraction.

Investigation of the antimicrobial activity at safe levels for eukaryotic cells of a low power atmospheric pressure inductively coupled plasma source.

Low power atmospheric pressure inductively coupled thermal plasma sources integrated with a quenching device (cold ICP) for the efficient production of biologically active agents have been recently developed for potential biomedical applications. In the present work, in vitro experiments aimed at assessing the decontamination potential of a cold ICP source were carried out on bacteria typically associated with chronic wounds and designed to represent a realistic wound environment; further in vitro experiments were performed to investigate the effects of plasma-irradiated physiological saline solution on eukaryotic cells viability. A thorough characterization of the plasma source and process, for what concerns ultraviolet (UV) radiation and nitric oxide production as well as the variation of pH and the generation of nitrates and nitrites in the treated liquid media, was carried out to garner fundamental insights that could help the interpretation of biological experiments. Direct plasma treatment of bacterial cells, performed at safe level of UV radiation, induces a relevant decontamination, both on agar plate and in physiological saline solution, after just 2 min of treatment. Furthermore, the indirect treatment of eukaryotic cells, carried out by covering them with physiological saline solution irradiated by plasma, in the same conditions selected for the direct treatment of bacterial cells does not show any noticeable adverse effect to their viability. Some considerations regarding the role of the UV radiation on the decontamination potential of bacterial cells and the viability of the eukaryotic ones will be presented. Moreover, the effects of pH variation, nitrate and nitrite concentrations of the plasma-irradiated physiological saline solution on the decontamination of bacterial suspension and on the viability of eukaryotic cells subjected to the indirect treatment will be discussed. The obtained results will be used to optimize the design of the ICP source for an effective production of reactive species, while keeping effluent temperature and UV radiation at values compatible with biomedical treatments.

The effect of pH on stable iron isotope exchange and fractionation between aqueous Fe(II) and goethite

Enriched Fe isotope tracer studies demonstrate that aqueous Fe(II) undergoes electron transfer and atom exchange with goethite. Such processes influence contaminant fate and trace-element mobility, and result in stable Fe isotope fractionation in both biological and abiological processes. To date, the majority of experimental studies of aqueous Fe(II) and Fe oxide interactions have been done at circumneutral pH. The effect of pH variations on the rate and extent of Fe isotope exchange between aqueous Fe(II) and iron oxide minerals, as well as the natural mass-dependent fractionation between these species, has not been adequately explored. Here, the three-isotope method (57Fe–56Fe–54Fe), using an enriched 57Fe tracer, was used to investigate the effect of pH (between 2.5 and 7.5) on the rate and extent of isotopic exchange. 56Fe/54Fe ratios were used to determine the natural, mass-dependent stable isotope fractionation, between aqueous Fe(II) and goethite. Three Fe(II) solutions differing in their initial 56Fe/54Fe ratios were used to approach isotopic equilibrium from multiple directions. The 57Fe-enriched tracer data indicate that the extent of isotopic exchange between Fe(II)aq and goethite was positively correlated with pH, where the least amount of exchange occurred at the lowest pH. Similarly, initial kinetic isotope fractionations were influenced by pH; at low pH, minimal kinetic isotope effects were observed relative to large effects at high pH, suggesting a relation between the extent of sorbed Fe(II) and kinetic isotope effects. Continued exchange over time at high pH, however, erases the initial kinetic isotope effects, and the system fundamentally reached isotopic equilibrium by the end of the experiment. Our results show that the interplay between kinetic and equilibrium effects may prevent confident extrapolation to infer equilibrium fractionation factors when only small amounts of Fe exchange occur.