Buffering Agent Research Articles

Use of a New Organic Complexing and Buffer Agent for Zn(S,O) Deposition for High-Efficiency Cu(In,Ga)Se2-Based Solar Cells

Chemical-bath-deposited (CBD) Zn(S,O) is one of the most studied and promising Cd-free buffer layers for Cu(In,Ga)Se2 (CIGSe) -based solar cells and has already demonstrated its potential to lead to high-efficiency solar cells. However, CBD Zn(S,O) presents some inconveniences compared with a classic CBD cadmium sulfide (CdS) buffer. Indeed, Zn(S,O) deposition time, important ammonia concentration, and metastable behavior of the final devices are obstacle to its generalized use. A new complexing agent, i.e., morpholine, has been mixed to ammonia as a buffer and complexing agent. From a theoretical study, the mix of these leads to the formation of a majority zinc-morpholine complex instead of the classic zinc-ammonia one. In situ studies have shown an increase in the deposition rate, allowing us to reduce the concentration of the other reactants. Scanning electron microscopy and X-ray photoelectron spectroscopy measurements have shown that the deposited material presents equivalent covering properties and sulfur incorporation ([S]/([S] + [O]) ratio) to the one determined using standard formulations. Finally, CIGSe-based devices have been realized using the optimized CBD Zn(S,O) as a buffer layer. Higher efficiencies than CdS-buffered reference are measured, and no metastability is observed.

The construction of a sandwich structured Co3O4@C@PPy electrode for improving pseudocapacitive storage.

Sandwich structured hybrids consisting of a Co3O4 nanowire as the core, amorphous carbon (C) as the inner shell and a polypyrrole (PPy) outer layer as the exodermis are synthesized via a hydrothermal method and constant current electropolymerization. The formation mechanism and growth stage of PPy on carbon surfaces is investigated and it was discovered that PPy layer thickness, corresponding to nucleation time of the polymer, as the dynamic factor, can influence the pseudocapacitive properties of the obtained composites. The carbon layer acts as both a network to increase the electric conductivity and a buffer agent to reduce volume expansion of Co3O4 during ion insertion/extraction to achieve higher capacitance and better cyclic stability. So for a capacitor, the Co3O4@C@PPy electrode delivers a higher areal capacitance of 2.71 F cm−2 at 10 mA cm−2 (1663 F g−1 at 6.1 A g−1) and improved rate capability compared to Co3O4 and Co3O4@C. An asymmetric device is assembled by the Co3O4@C@PPy hybrids as a cathode and a relatively high energy density of 63.64 W h kg−1 at a power density of 0.54 kW kg−1 is obtained, demonstrating that the sandwich structured Co3O4@C@PPy hybrids have enormous potential for high-performance pseudocapacitors.

Biodegradable in situ Gel for Subcutaneous Administration of Simvastatin for Osteoporosis

Many observational studies and animal research has revealed that statins appear to enhance osteoblastic activity and diminish osteoclast activity, hence increasing bone density. This study was aimed to prepare and characterize biodegradable in situ gel for subcutaneous administration of simvastatin for the treatment of osteoporosis. Biodegradable in situ gel was prepared using chitosan as biodegradable polymer and β-glycerol phosphate disodium salt hydrate as a buffering agent to achieve in situ gelation at physiological pH and temperature. In situ gel was characterized in terms of pH, gelling capacity, drug content, sedimentation volume, resuspendability, syringeability, in vitro drug release, particle size and zeta potential. The optimized formulation, containing 1.25 % w/v chitosan and 1 % β-glycerol phosphate disodium salt hydrate, had good gelling capacity at physiological temperature and pH. It had a pH of 5.85±0.5, drug content of 97.1±1.2 % and sedimentation volume of 0.42±0.04. In vitro drug release was found to be 98.7±1.5 % in 7 days. Particle size, zeta potential and viscosity were found to be 7.07±0.3 μm, 12.5±1.5 mV and 22.66±1.8 cp, respectively. Hence, the developed biodegradable in situ gel administered subcutaneously can prove to be an effective alternative drug delivery system for the treatment of osteoporosis.

Exceptionally rapid oxime and hydrazone formation promoted by catalytic amine buffers with low toxicity.

Hydrazone and oxime bond formation between α-nucleophiles (e.g. hydrazines, alkoxy-amines) and carbonyl compounds (aldehydes and ketones) is convenient and is widely applied in multiple fields of research. While the reactants are simple, a substantial drawback is the relatively slow reaction at neutral pH. Here we describe a novel molecular strategy for accelerating these reactions, using bifunctional buffer compounds that not only control pH but also catalyze the reaction. The buffers can be employed at pH 5-9 (5-50 mM) and accelerate reactions by several orders of magnitude, yielding second-order rate constants of >10 M-1 s-1. Effective bifunctional amines include 2-(aminomethyl)imidazoles and N,N-dimethylethylenediamine. Unlike previous diaminobenzene catalysts, the new buffer amines are found to have low toxicity to human cells, and can be used to promote reactions in cellular applications.

Denitrification of water in a microbial fuel cell (MFC) using seawater bacteria

The sea contains various microbes which have an ability to reduce and oxidize substances like iron, sulphur, and nitrate. Most of these processes happen in the seawater, but can also be applied for purification of wastewater. In the present work, a consortium of seawater bacteria has been used for the first time in a microbial fuel cell to reduce nitrate in synthetic water samples and produce electricity by oxidizing organic matter. The concentrations of nitrate and nitrite were reduced to well below their permissible limits. Moreover, the growth of the bacterial consortium in cathode causes an increased electricity production in the cell because of the increased bacterial activity. The performance of the cell with a bicarbonate buffered solution in the cathode was superior to that obtained with the commonly used phosphate buffered solution. As bicarbonate is the natural buffering agent found in the sea, the use of bicarbonate buffered solutions is eco-friendly. The same seawater bacterial consortium was used in both the anode and the cathode, confirming their adaptability to different environments. Unfortunately, denitrification was accompanied by the generation of high concentrations of ammonium in the anode and the cathode, probably because of the use of nitrogen gas for sparging the anolyte. This aspect merits further investigation.

Hydroxamate column-based purification of zirconium-89 (89Zr) using an automated fluidic platform

Zirconium-89 (89Zr) is a long-lived (t1/2 = 78.4h) positron-emitting isotope that is useful for positron emission tomography (PET) based diagnostic imaging using radiolabeled antibodies. Hydroxamate resin columns are predominantly used for the purification of 89Zr from cyclotron bombarded natY targets dissolved in strong HCl. 89Zr is conventionally eluted from the resin in 1M oxalic acid (H2C2O4), a complexant that is conducive to follow-on binding of 89Zr through a transchelation process to the deferoxamine siderophore. In the present study, we determined that a lower concentration of H2C2O4 eluent (0.8M) is adequate to efficiently remove 89Zr from a column containing 100mg hydroxamate resin. As a result, less buffering agents are needed to be added to the 89Zr product fraction prior to labeling. A simple automated fluidic system prototype has been developed to perform the steps required for 89Zr purification using a hydroxamate resin column (column conditioning in HCl, Y target dissolution, dissolved target solution load onto column, column washes using HCl and water, and 89Zr elution). The system performance was evaluated using several cyclotron bombarded Y targets; 89Zr product fractions demonstrated excellent chemical recoveries from these targets, with 1.0mL product volumes yielding 89±2% of the column elution peak activity and 84±2% of 89Zr recovered from the target (at EOB). These results compare favorably with previously published 89Zr product volumes and yields, despite the lower concentration of H2C2O4 eluent employed. Transchelation of resulting 89Zr product fractions was performed to assess product quality. The effective specific activity (ESA) ranged between 44(7) and 109(22) TBq·mmole-1, while the bindable metals concentration, a metric introduced for assessing and comparing product purity, ranged between 43(7) and 115(27) nmole·g-1.

Bile Acid Recognition by Mouse Ileal Bile Acid Binding Protein

Ileal bile acid binding protein (I-BABP, gene name FABP6) is a component of the bile acid recycling system, expressed in the ileal enterocyte. The physiological role of I-BABP has been hypothesized to be either an intracellular buffering agent to protect against excess intracellular bile acids or separately as a modulator of bile acid controlled transcription. We investigated mouse I-BABP (mI-BABP) to understand the function of this protein family. Here, we studied energetics and site selectivity of binding with physiological bile acids using a combination of isothermal calorimetric analysis and NMR spectroscopy. We found that the most abundant bile acid in the mouse (β-muricholic acid) binds with weak affinity individually and in combination with other bile acids. Further analysis showed that mI-BABP like human I-BABP (hI-BABP) specifically recognizes the conjugated form of cholic acid:chenodeoxycholic acid (CA:CDCA) in a site-selective manner, displaying the highest affinity of any bile acid combination tested. These results indicate that I-BABP specifically recognizes the ligand combination of CDCA and CA, even in a species such as the mouse where CDCA only represents a trace component of the physiological pool. Specific and conserved recognition of the CDCA and CA ligand combination suggests that I-BABP may play a critical role in the regulation of bile acid signaling in addition to its proposed role as a buffering agent.

THE DYNAMICS OF PH, EC AND REDOX OF POND SOIL AFTER APPLICATION OF HUMIC ACID.

10Oct 2017 THE DYNAMICS OF PH, EC AND REDOX OF POND SOIL AFTER APPLICATION OF HUMIC ACID. Munawar Ali , Wanti Mindari and Eddy Poernomo. Department of Environment, Faculty of Civil and Environmental Engineering, Universitas Pembangunan Nasional "Veteran" East Java, Indonesia. Department of Soil Science - Agrotechnology, Faculty of Agriculture, Universitas Pembangunan Nasional "Veteran" East Java, Indonesia. Departemen Of Administration Businiss Universitas, Faculty Of Political Social Since Pembangunan Nasional ?Veteran? East Java, Indonesia

Selective Reduction of Nitrite to Nitrogen with Carbon-Supported Pd–AOT Nanoparticles

The catalytic reduction of nitrite in water with hydrogen has been studied using a new strategy to control selectivity. The catalysts used are based on size-controlled Pd–AOT nanoparticles, synthesized via sodium bis[2-ethylhexyl] sulfosuccinate (AOT)/isooctane reverse microemulsion, supported on activated carbon. The most remarkable feature of the catalysts is the negligible selectivity toward ammonium, which is attributed to shielding of Pd NPs by AOT and blockage of the active centers related to ammonium generation. The shielding by AOT also reduces the activity of Pd–AOT NPs, which can be overcome by immobilization on carbon and thermal treatment at mild conditions (473 K, N2 atmosphere), although excessive removal of AOT results in higher ammonium production. Complete nitrite conversion with total selectivity to N2 was achieved at room temperature for the Pd–AOT/C catalysts at controlled pH media using CO2 as buffer agent. Moreover, the catalytic activity results at controlled pH show that the nitrit...

Measurement of europium (III)/europium (II) couple in fluoride molten salt for redox control in a molten salt reactor concept

The fluoride molten salt such as FLiNaK and FLiBe is one of the coolant candidates for the next generation nuclear reactor concepts, for example, the fluoride salt cooled high temperature reactor (FHR). For mitigating corrosion of structural materials in molten fluoride salt, the redox condition of the salts needs to be monitored and controlled. This study investigates the feasibility of applying the Eu3+/Eu2+ couple for redox control. Cyclic voltammetry measurements of the Eu3+/Eu2+ couple were able to obtain the concentrations ratio of Eu3+/Eu2+ in the melt. Additionally, the formal standard potential of Eu3+/Eu2+ was characterized over the FHR's operating temperatures allowing for the application of the Nernst equation to establish a Eu3+/Eu2+ concentration ratio below 0.05 to prevent corrosion of candidate structural materials. A platinum quasi-reference electrode with potential calibrated by potassium reduction potential is shown as reliable for the redox potential measurement. These results show that the Eu3+/Eu2+ couple is a feasible redox buffering agent to control the redox condition in molten fluoride salts.

Optimization of the expression, purification and polymerase activity reaction conditions of recombinant human PrimPol.

Human PrimPol is a DNA primase/polymerase involved in DNA damage tolerance and prevents nuclear genome instability. PrimPol is also localized to the mitochondria, but its precise function in mitochondrial DNA maintenance has remained elusive. PrimPol works both as a translesion (TLS) polymerase and as the primase that restarts DNA replication after a lesion. However, the observed biochemical activities of PrimPol vary considerably between studies as a result of different reaction conditions used. To reveal the effects of reaction composition on PrimPol DNA polymerase activity, we tested the polymerase activity in the presence of various buffer agents, salt concentrations, pH values and metal cofactors. Additionally, the enzyme stability was analyzed under various conditions. We demonstrate that the reaction buffer with pH 6–6.5, low salt concentrations and 3 mM Mg2+ or 0.3–3 mM Mn2+ cofactor ions supports the highest DNA polymerase activity of human PrimPol in vitro. The DNA polymerase activity of PrimPol was found to be stable after multiple freeze-thaw cycles and prolonged protein incubation on ice. However, rapid heat-inactivation of the enzyme was observed at 37ºC. We also for the first time describe the purification of human PrimPol from a human cell line and compare the benefits of this approach to the expression in Escherichia coli and in Saccharomyces cerevisiae cells. Our results show that active PrimPol can be purified from E. coli and human suspension cell line in high quantities and that the activity of the purified enzyme is similar in both expression systems. Conversely, the yield of full-length protein expressed in S. cerevisiae was considerably lower and this system is therefore not recommended for expression of full-length recombinant human PrimPol.

A Novel Technique to Enhance Dissolution Rate of Cilnidipine Using Liquisolid Compact and Wet Granulation

The main objective of the work was to improve the dissolution rate of the drug, Cilnidipine (CLD) by using the liquisolid compact technique and wet granulation. Cilnidipine drug is poorly soluble in water and it’s highly soluble in higher pH. In this study drug is solubilize in tween 80 and sodium hydroxide and meglumine solution. And then drug solution binding on Pearlitol SD 200. PVP K30 used as a binder and crospovidone used as a disintegrant. Sodium hydroxide and meglumine used as a buffering agent for basic media preparation. The drug release rates of tablets which prepared by liquisolid compact have higher solubility and dissolution than conventional tablets.

Pilot scale fermentation coupled with anaerobic digestion of food waste - Effect of dynamic digestate recirculation

The anaerobic digestion in double stage is a known and adopted system, but the process productivity and optimization still remain an aspect to investigate. The accumulation of organic acids (produced during fermentative metabolism) in the first stage generally decrease the pH below the optimal values (5.5). A pre-evaluation strategy by control charts for further pH control is proposed. The process combines in series the 1st Fermentation process and the 2nd Anaerobic Digestion process, using the recirculation of the anaerobic digestion effluent, rich in buffer agents, to control the pH in the 1st stage. The recycle ratio becomes a further operating parameter that should be properly managed. A proper management as dynamic recirculation flow allows to maintain the pH of the first phase to values higher than 5. Specific hydrogen production, specific methane production and volatile fatty acid production; 170 L/kgTVS at 40% H2, 750 L at 67% CH4 and 14 gCOD/L VFA were obtained respectively.

Effects of pH buffering agents on the anaerobic hydrolysis acidification stage of kitchen waste

This study investigated effects of initial pH buffering agents on the lab-scale anaerobic hydrolysis acidification stage of kitchen waste (KW). Different cheap, available and suitable buffering agents (NaOH(s), NaOH(l), CaO(s)-NaOH, KOH(l)-NaOH, K2HPO4(s)-KOH, Na2CO3(s)-NaOH) were added under optimal adjusting mode (first two days: per 16h, after: one time per day) which was obtained in previous work. The effects of buffering agents were evaluated according to indexes of pH, VFAs, NH4+-N, TS, VS, VS/TS, TS and VS removal rate. The results showed treatment 5 with adding K2HPO4-KOH buffering agents had the most stable pH (6.7–7.0). Also treatment 5, 2, 4 and 6 provided stable pH ranging in 5–8. Among the treatments, treatment 6 with adding Na2CO3 as initial buffering agents and 10mol/L NaOH as regulator was chosen as the optimal mode for highest VFAs content (44.05g/L) with high acetic acid and butyrate acid proportion (42.64%), TS and VS removal rate (44.84% and 58.67%, respectively), low VS/TS ratio (58.55), fewer adding dosage and low adjusting frequency. The VFAs content of treatment 6 at the end of hydrolysis acidification stage could be used for methanogenic phase of anaerobic two-phase digestion. Thus, treatment 6 (adding Na2CO3 as initial buffering agents and 10mol/L NaOH as regulator) with highest VFAs content and TS and VS removal rate could be considered using in anaerobic hydrolysis acidification stage pH adjustment.

Buffers Strongly Modulate Fibrin Self-Assembly into Fibrous Networks

Fibrin is a plasma protein with a central role in blood clotting and wound repair. Upon vascular injury, fibrin forms resilient fibrillar networks (clots) via a multistep self-assembly process, from monomers, to double-stranded protofibrils, to a branched network of thick fibers. In vitro, fibrin self-assembly is sensitive to physicochemical conditions like the solution pH and ionic strength, which tune the strength of the noncovalent driving forces. Here we report a surprising finding that the buffer—which is necessary to control the pH and is typically considered to be inert—also significantly influences fibrin self-assembly. We show by confocal microscopy and quantitative light scattering that various common buffering agents have no effect on the initial assembly of fibrin monomers into protofibrils but strongly hamper the subsequent lateral association of protofibrils into thicker fibers. We further find that the structural changes are independent of the molecular structure of the buffering agents as well as of the activation mechanism and even occur in fibrin networks formed from platelet-poor plasma. This buffer-mediated decrease in protofibril bundling results in a marked reduction in the permeability of fibrin networks but only weakly influences the elastic modulus of fibrin networks, providing a useful tuning parameter to independently control the elastic properties and the permeability of fibrin networks. Our work raises the possibility that fibrin assembly in vivo may be regulated by variations in the acute-phase levels of bicarbonate and phosphate, which act as physiological buffering agents of blood pH. Moreover, our findings add a new example of buffer-induced effects on biomolecular self-assembly to recent findings for a range of proteins and lipids.

Maintenance fluid therapy in a tertiary hospital: A prevalence study

Abstract Objective To assess the types of maintenance fluids used in our hospital, comparing their volume and composition to the standards recommended by the guidelines. Material and methods Observational, cross-sectional study. Volume and type of fluid therapy administered during 24 h to patients admitted to various hospital departments were recorded. Patients receiving fluid therapy because of water-electrolyte imbalance were excluded. Results Out of 198 patients registered, 74 (37.4%) were excluded because they did not meet the criteria for inclusion. Mean administered volume was 2500 cc/day. Mean daily glucose dose was 36 g per 24 h (SD: 31.4). The most frequent combination included normal saline solution (NSS) and glucose 5% (64.4%). Mean daily dose of sodium and chlorine was, respectively, 173 mEq (SD: 74.8) and 168 mEq (SD: 75), representing a surplus daily dose of +87.4 mEq and +85 mEq. Potassium, magnesium and calcium daily deficit was, respectively, −50 mEq, −22 mEq and −21 mEq per day. Buffer administration was exceptional, bicarbonate (2.29%), acetate (1.29%), lactate (1.15%) and gluconate (1.10%) being the buffering agents most frequently used. Conclusion NNS is the most frequently used solution. In contrast to excess doses of sodium and chlorine, there is a great deficit of other ions, buffering agents and caloric intake in the fluid therapy regimens that are usually prescribed.

A Simple Approach to Achieve Self‐Buffering Protic Ionic Liquid‐Water Mixtures

AbstractIonic liquid (IL)‐water mixtures have drawn increasing attention in a range of applications ranging from chemical synthesis and separation to bioscience and energy applications. The acid‐basic nature of ILs is often an important property to be considered when selecting and designing ILs. Herein, we evaluated this IL property by correlating the stoichiometry of a protic IL and pH of IL‐water mixtures. We then developed a simple method to achieve self‐buffering protic IL‐water mixtures by titrating buffering agents. The rule of buffering protic IL‐water mixtures was proposed to be linearly related to pIL ion concentration and correlated with ionicity. Through this approach, self‐buffering capability can be achieved in protic IL‐water mixtures without significantly changing the ion concentration.

Toward a better understanding of the emulsion polymerization of butadiene. I. Continuous conductivity measurements

ABSTRACTContinuous conductivity measurements were performed during the batch emulsion polymerization of butadiene along with kinetic and particle size measurements. The critical monomer conversion was obtained around 55% and the rate of polymerization was correlated to the surfactant concentration with an exponent of 0.35 which was not in agreement with the exponent offered by Smith and Ewart. In addition, the evolution of some particle‐related quantities such as particle size and number of particles during the three intervals of the emulsion polymerization and their agreements with Smith‐Ewart mechanism were investigated. The behavior of conductivity in the emulsion polymerization of butadiene normally containing a buffering agent was found to be completely different from the unbuffered one. Comparison of the conductivity profiles with the kinetic and particle‐related quantities represented that the conductivity of the reaction mixture is very sensitive to the changes in the particle size so that any small change in the forms of nucleation, growth, and coagulation is clearly observed in the conductivity profiles. Furthermore, the conductimetric data are capable of determining some important points during the polymerization such as the beginning of the reaction that can be important from the industrial process control point of view. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2017,134, 45262.

Impact of glutathione metabolism on zinc homeostasis in Saccharomyces cerevisiae.

Zinc is a crucial mineral for all organisms as it is an essential cofactor for the proper function of a plethora of proteins and depletion of zinc causes oxidative stress. Glutathione is the major redox buffering agent in the cell and therefore important for mitigation of the adverse effects of oxidative stress. In mammalian cells, zinc deficiency is accompanied by a glutathione depletion. In the yeast Saccharomyces cerevisiae, the opposite effect is observed: under low zinc conditions, an elevated glutathione concentration is found. The main regulator to overcome zinc deficiency is Zap1p. However, we show that Zap1p is not involved in this glutathione accumulation phenotype. Furthermore, we found that in glutathione-accumulating strains also the metal ion-binding phytochelatin-2, which is an oligomer of glutathione, is accumulated. This increased phytochelatin concentration correlates with a lower free zinc level in the vacuole. These results suggest that phytochelatin is important for zinc buffering in S. cerevisiae and thus explains how zinc homeostasis is connected with glutathione metabolism.

Inclusion complex of antiasthmatic compound with 2-hydroxypropyl-β-cyclodextrin: Preparation and physicochemical properties

This work aims at obtaining 2-hydroxypropyl-β-cyclodextrin inclusion complex with an original antiasthmatic compound in buffer solution and solid state with higher solubility and, hence, bioavailability. The compound solubility with different 2-hydroxypropyl-β-cyclodextrin concentrations has been studied by the phase solubility method. The linearity of the phase solubility diagrams is classified as an AL type and indicates the formation of inclusion complexes with 1:1 stoichiometry. The complex stoichiometry has been confirmed by the Job's method. The solubility of the studied compound in buffer has been considerably increased by complexation with 2-hydroxypropyl-β-cyclodextrin. Complexation stability constants and thermodynamic parameters have been calculated. The obtained inclusion complexes in solid state have been studied by the differential scanning calorimetry, Fourier transform infrared spectroscopy and X-ray powder diffraction. The kinetic characteristics of dissolution for the supramolecular complex have been obtained.