Buffering Agent Research Articles

Interference of peritoneal dialysis fluids with cell cycle mechanisms.

Peritoneal dialysis fluids (PDF) differ with respect to osmotic and buffer compound, and pH and glucose degradation products (GDP) content. The impact on peritoneal membrane integrity is still insufficiently described. We assessed global genomic effects of PDF in primary human peritoneal mesothelial cells (PMC) by whole genome analyses, quantitative real-time polymerase chain reaction (RT-PCR) and functional measurements. PMC isolated from omentum of non-uremic patients were incubated with conventional single chamber PDF (CPDF), lactate- (LPDF), bicarbonate- (BPDF) and bicarbonate/lactate-buffered double-chamber PDF (BLPDF), icodextrin (IPDF) and amino acid PDF (APDF), diluted 1:1 with medium. Affymetrix GeneChip U133Plus2.0 (Affymetrix, CA, USA) and quantitative RT-PCR were applied; cell viability was assessed by proliferation assays. The number of differentially expressed genes compared to medium was 464 with APDF, 208 with CPDF, 169 with IPDF, 71 with LPDF, 45 with BPDF and 42 with BLPDF. Out of these genes 74%, 73%, 79%, 72%, 47% and 57% were downregulated. Gene Ontology (GO) term annotations mainly revealed associations with cell cycle (p = 10(-35)), cell division, mitosis, and DNA replication. One hundred and eighteen out of 249 probe sets detecting genes involved in cell cycle/division were suppressed, with APDF-treated PMC being affected the most regarding absolute number and degree, followed by CPDF and IPDF. Bicarbonate-containing PDF and BLPDF-treated PMC were affected the least. Quantitative RT-PCR measurements confirmed microarray findings for key cell cycle genes (CDK1/CCNB1/CCNE2/AURKA/KIF11/KIF14). Suppression was lowest for BPDF and BLPDF, they upregulated CCNE2 and SMC4. All PDF upregulated 3 out of 4 assessed cell cycle repressors (p53/BAX/p21). Cell viability scores confirmed gene expression results, being 79% of medium for LPDF, 101% for BLPDF, 51% for CPDF and 23% for IPDF. Amino acid-containing PDF (84%) incubated cells were as viable as BPDF (86%). In conclusion, PD solutions substantially differ with regard to their gene regulating profile and impact on vital functions of PMC, i.e. on cells known to be essential for peritoneal membrane homeostasis.

Effect of supercritical water shell on cavitation bubble dynamics**Project supported by the National Natural Science Foundation of China (Grant Nos. 11174145 and 11334005).

Based on reported experimental data, a new model for single cavitation bubble dynamics is proposed considering a supercritical water (SCW) shell surrounding the bubble. Theoretical investigations show that the SCW shell apparently slows down the oscillation of the bubble and cools the gas temperature inside the collapsing bubble. Furthermore, the model is simplified to a Rayleigh–Plesset-like equation for a thin SCW shell. The dependence of the bubble dynamics on the thickness and density of the SCW shell is studied. The results show the bubble dynamics depends on the thickness but is insensitive to the density of the SCW shell. The thicker the SCW shell is, the smaller are the wall velocity and the gas temperature in the bubble. In the authors’ opinion, the SCW shell works as a buffering agent. In collapsing, it is compressed to absorb a good deal of the work transformed into the bubble internal energy during bubble collapse so that it weakens the bubble oscillations.

Advanced TALSPEAK Separations Using a Malonate Buffer System

The extraction behavior of lanthanides and americium has been evaluated under Advanced TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus-reagent Extraction from Aqueous Komplexes) conditions using malonic acid as the aqueous buffering agent. The extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) was used as an organic phase liquid cation exchanger in n-dodecane diluent, while N-(hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) served as a selective aqueous holdback reagent. Extractions conducted from malonate media exhibit a pH profile that flattens as the concentration of malonate is increased up to 1.0 M malonate. This relatively flat extraction behavior from pH 2.5–4.0 is reminiscent of previous studies on Advanced TALSPEAK in lactate media. The extraction kinetics with other carboxylic acid buffers as well as the effects of varying HEDTA, HEH[EHP], and malonate concentration are compared.

Synthesis and characterization of α-MoO3 nanobelt composite positive electrode materials for lithium battery application

α-MoO3 and PEO surfactant MoO3 nanobelts were synthesized by a solvothermal method. The morphology and nanostructure of samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Bare α-MoO3 and 12.5wt% PEO surfactant MoO3 nanobelts have an initial specific capacities of 279 and 352mAhg−1, respectively, at constant current density 30mAg−1 with potential range of 1.5–4.0V vs. Li/Li+. While MoO3 is modified by the intercalation of PEO, it is effectively shielded against electrostatic interaction between the MoO3 interlayer and Li+ ions. We reported positive material, a nanocomposite of MoO3 coated with polyethylene oxide. It presents good cycling stability due to existence of the conductive and protective polyethylene oxide coating and the nanobelt morphology of MoO3. The polyethylene oxide acts as a conducting matrix, a binder and an active material, as well as a volume change buffer agent, which holds the MoO3 particles in place during the discharge cycles. The cyclic voltammograms of the 12.5wt% PEO surfactant MoO3 nanobelt composite displayed better cyclic performance compared with pure MoO3 nanobelts. The specific capacity of the pure MoO3 nanobelts and 12.5wt% PEO surfactant MoO3 nanobelts exhibit as 199mAhg−1 and 225mAhg−1, respectively, after 9 cycles, suggesting that the stability of surfactant material is worthy.

Improved Catalytic Lifetime of H2SO4 for Isobutane Alkylation with Trace Amount of Ionic Liquids Buffer

Trace amounts of ionic liquids have been mixed in sulfuric acid to enhance the catalytic performance for the alkylation of isobutane with butene. The experimental results from batch reactors indicated that the reaction efficiency was significantly improved. The effective catalytic lifetime of concentrated H2SO4 mixed with [Bmim][SbF6] was twice compared with pure H2SO4. Under the optimal conditions, the alkylate research octane (RON) reached 98, and the selectivity of C8 was 90%. The ionic liquids with SbF6 anion worked similar to buffer agents, which were in favor of keeping the acid strength of catalytic system, slowing the growth of acid soluble oil, and reducing acid consumption. In conclusion, the new catalytic system of acid and trace amounts of ionic liquids is very promising to substitute the old catalytic system of concentrated H2SO4 alone for the alkylation.

Characterizing the Polyethylenimine Polymer Dynamics as a pH Buffer for its use as DNA Aggregating Agent

In recent years Polyethylenimine (PEI), a positively charged polymer, has gained much attention for its use as a DNA complexing agent. The PEI charge comes from the protonation of tertiary amine groups on its backbone. Since about 50% of the amines are still protonable at physiological pH, the polymer can act like a buffering agent. This buffering property protects the DNA-PEI complex in the acidic environment of cell-uptake vesicles. From a polymer biophysics perspective, PEI is a hydrophobic, semi-flexible, weak-base polyelectrolyte; it remains in equilibrium with an aggregated phase and the free polymer dynamics is governed by competing intra-and inter-chain charge repulsion. We examined the role of PEI polymer biophysics in its biologically-important function as a pH buffering agent. Using Dynamic Light Scattering, the change in the PEI backbone elongation and its aggregation state was visualized as a function of H+ addition to the backbone. Separate concentration regimes were examined for intra- and inter-chain charge repulsion. We report an interesting interplay between PEI charging and monomer aggregation occurring during the pH buffering.

In Situ Electrochemical Dilatometric Study of Fe3O4/Reduced Graphene Oxide Nanocomposites as Anode Material for Lithium Ion Batteries

In situ electrochemical dilatometry (ECD) was performed on Fe3O4/reduced graphene oxide (RGO) nanocomposite during galvanostatic charge and discharge tests in order to investigate the volume change of the metal-oxide/RGO nanocomposites and the role of RGO as a buffering agent in the composite. Fe3O4/RGO nanocomposite with Fe3O4 particles (2−3 nm in size) was successfully prepared through selective heterogeneous precipitation of nanosized Fe3O4 on RGO. A combined analysis of the thickness (t)-change curve of the composite electrode measured via ECD and the differential t-change curve along with the charge/discharge and differential capacity curves clearly indicated the buffering role of RGO in the composite, which exhibited excellent energy efficiency and cycling stability.

Preparation and characterization of physicochemical properties of N, N-diethyl-meta-toluamide niosomes.

Introduction:The insect repellent compounds are used to protect humans, animals and plants against insect bites. Aromatic amides have insect repellent effects. N,N-diethyl-meta-toluamide (DEET) (C12 H17 NO) is one of the best insect repellents has been used for many years. DEET is a colorless, odorless liquid that is approximately insoluble in water and soluble in glycerin, ethanol, and isopropyl alcohol. Due to the solubility problem of DEET, its topical formulations usually have alcoholic bases, but these kind of formulations increase skin permeation and also systemic absorption of DEET, which leads to some toxic effects. The main goal of this study was to prepare the formulation of DEET niosomes in a topical dosage form with suitable stability properties.Materials and Methods:Three different methods were used to prepare niosome formulations: Dehydration rehydration vesicle method, direct mixing method, homogenizer method. Sorbitan surfactants, cholesterol, polyoxyethylenecetyl, phosphate buffer (pH 7.4), and charge inductive compounds like cetyltrimethylammonium bromide were used to provide a net negative charge to the final membrane structure. A high-performance liquid chromatography method was then used for the determination of the loaded DEET.Results:A large number of niosomes were multi-layered and have a spherical shape. In comparison, syringe method against direct mixing is more appropriate because of creation MLV and uniform niosomes but the best method is homogenizer method. Drug entrapment was between 14% and 21% in selected formulation.Conclusion:According to this study, homogenizing method can be used for formulation of DEET in niosome form in topical formulations.

Influence of Buffer Agent Concentration on the Optical Properties from CdS Nanocrystals on Silicon Nanoporous Pillar Array

The chemical bath deposition (CBD) method is very crucial to the reaction rate. Generally, the rate can be controlled through tuning buffer agent concentration. CdS nanocrystals on the silicon nanoporous pillar array (CdS/Si-NPA) have been prepared through the CBD method. By varying the buffer agent concentration, the reaction rates can be tuned. The diffraction peaks of hexagonal CdS and Cd can be observed due to the reduction of Cd2+caused by the silicon nanoporous pillar array. The average size of CdS nanocrystals is decreased with the increasing buffer agent concentration and the optical band gaps from CdS nanocrystals are increased. From the photoluminescence of CdS/Si-NPA, it can be observed that the blue emissions are independent of the buffer agent concentration and the green emissions show blue shift with the increasing buffer agent concentration.

PH control using polymer-supported phosphonic acids as reusable buffer agents

To reduce phosphorus effluents from phosphate buffers, we use polymer-supported phosphonic acids as heterogenous and reusable buffer agents for pH control of enzyme catalysis.

Biochemical, Biomedical and Metabolic Aspects of Imidazole-Containing Dipeptides with the Inherent Complexity to Neurodegenerative Diseases and Various States of Mental Well-Being: A Challenging Correction and Neurotherapeutic Pharmaceutical Biotechnology for Treating Cognitive Deficits, Depression and Intellectual Disabilities.

The activities of carnosine (β-alanyl-L-histidine), carnosine imidazole containing dipeptide based derivatives (N-acetylcarnosine, carcinine, homocarnosine) and a carnosine degrading enzyme (serum carnosinase (EC 3.4.13.20); [human tissue carnosinase (EC 3.4.13.3), CN2 (CNDP2)] ) activities have been discrepantly linked to neuropathophysiological processes. Approximately 82% of the U.S. population will experience normal age-related cognitive decline, as compared to the precipitous losses that are associated with dementing disorders. Interventions designed to promote health and function through everyday activity and specific pharmaco-nutritional therapeutic treatments may enhance brain plasticity in key regions that support executive function. Cognitive health is multidimensional cascade of functions. It encompasses an array of functions, including general intellectual ability, memory, language, allowing a person to interact effectively and appropriately with the environment. The risk factors for reduced physical and cognitive functions in elderly people, as identified in longitudinal studies, relate to comorbidities, critical care situations, physical and psychosocial health, environmental conditions, social circumstances, nutrition, and lifestyle. Depression and dementia are both common in older adults; cognitive functioning declines slightly with normal aging; depression itself can be associated with cognitive impairment and dementia. In this study the role of carnosine and related neuron specific naturally-occurring endogenous imidazole-containing dipeptide pharmacoperones (N-acetylcarnosine, carcinine) is revealed presently in a surprisingly large amounts in long-lived human tissues to correct conformational abnormalities leading to distinct neurodegeneration and age-related disease states, treating cognitive deficits, depression and intellectual disabilities. Carnosine serves as a physiological buffering agent and a metal ion (e.g., zinc and copper) chelator, endowed with ferroxidase type activity; possess anti-aging functions, and free-radical scavenging activity, is capable of delaying senescence and extending the life-span of cultured human fibroblasts; is able to kill transformed cells and protect cells against aldehydes and amyloid peptide fragment. Carnosine and carcinine exhibit a well-documented anti-glycating activity against the glycation of proteins, including low-density lipoproteins, glucose degradation products, esterase, histones. A tissue carnosine-degrading enzyme (CN2) colocalized with the activity of histidine decarboxylase to histamine neurons in the hypothalamic tuberomammillary nucleus (TMN) plays a key role in the neuro-transmission and neuroregulation roles of imidazole-containing based dipeptides. Carnosine released from skeletal muscle during exercise may be transported into TMN-histamine neurons and hydrolyzed. Timing of carnosine present in the chicken broth, the specific patented nutraceutical composition (Can-C Plus™), 1% N-acetylcarnosine lubricant eye drops or 1% carcinine lubricant eye drops formulations are important targeting posology vehicles that are involved in many CNS functions through the central brain histamine system including the vision enhancement functions, physiological regulation of cognitive functions, arousal; anxiety; activation of the sympathetic nervous system; the stress-related release of hormones from the pituitary and of central aminergic neurotransmitters; antinociception; water retention and suppression of eating. The roles for the carnosine-stimulated/mediated neuronal histamine system are proposed as a danger and physiological response system active in protection from neurodegenerative diseases and in management of cognitive deficits, depression and intellectual disabilities.

Accounting for dissociation and photolysis: a review of the algal toxicity of triclosan.

Triclosan, an antimicrobial agent commonly used in down-the-drain consumer products, is toxic to freshwater microalgae. However, the rapid photolysis and pH-dependent dissociation of this compound may give rise to uncertainty in growth inhibition tests with freshwater microalgae, if these are not well characterized. Methods are presented to minimize these uncertainties by stabilizing pH with an organic buffering agent (Bis-Tris) and by the application of ultraviolet (UV) covers to remove UV wavelengths. Toxicity tests with these methods were in compliance with the validity criteria of the Organisation for Economic Co-operation and Development test 201, and no negative effects were seen in controls relative to the unmodified method. The methods were used for toxicity tests with triclosan at pH levels of 7.0, 8.0, and 8.5, yielding effective concentration, 10% values of 0.5 µg/L, 0.6 µg/L, and 12.1 µg/L, respectively. The observed change in toxicity with pH was proportional to the change in bioconcentration factor (BCF) as calculated using the cell model (a dynamic flux model based on the Fick-Nernst-Planck equations, in this case parameterized for an algal cell). Effect concentrations produced with the methods presented in the present study offer robust data on which to base risk assessment, and it is suggested that similar approaches be used to minimize uncertainty when other compounds that dissociate and photolyse are tested.

Aerobic oxidation of benzene to phenol over polyoxometalate-paired PdII-coordinated hybrid: Reductant-free heterogeneous catalysis

Aerobic oxidation of benzene was carried out over the organic–inorganic hybrid catalyst of [(C3CNpy)2Pd(OAc)2]2HPMoV2, a solid catalyst containing the Keggin polyoxometalate PMoV2 and noble metal Pd(OAc)2 in its ionic structure. The features of this heterogeneous reaction system were studied by tuning various reaction parameters including solvent selection, function of buffer agent, and effects of reaction time, reaction temperature and catalyst amount. The results show the high phenol yield of 9.8% without aided by any sacrificial reducing reagents. The conjugation of Pd(OAc)2 and PMoV2 within the ionic structure of [(C3CNpy)2Pd(OAc)2]2HPMoV2 that accounts for its high activity is preliminarily discussed.

Interactions between calcium and alpha-synuclein in neurodegeneration.

In Parkinson’s disease and some atypical Parkinson’s syndromes, aggregation of the α-synuclein protein (α-syn) has been linked to neurodegeneration. Many triggers for pathological α-syn aggregation have been identified, including port-translational modifications, oxidative stress and raised metal ions, such as Ca2+. Recently, it has been found using cell culture models that transient increases of intracellular Ca2+ induce cytoplasmic α-syn aggregates. Ca2+-dependent α-syn aggregation could be blocked by the Ca2+ buffering agent, BAPTA-AM, or by the Ca2+ channel blocker, Trimethadione. Furthermore, a greater proportion of cells positive for aggregates occurred when both raised Ca2+ and oxidative stress were combined, indicating that Ca2+ and oxidative stress cooperatively promote α-syn aggregation. Current on-going work using a unilateral mouse lesion model of Parkinson’s disease shows a greater proportion of calbindin-positive neurons survive the lesion, with intracellular α-syn aggregates almost exclusively occurring in calbindin-negative neurons. These and other recent findings are reviewed in the context of neurodegenerative pathologies and suggest an association between raised Ca2+, α-syn aggregation and neurotoxicity.

Anaerobic digestion of food waste stabilized by lime mud from papermaking process

The effects of lime mud from papermaking process (LMP) addition as buffer agent and inorganic nutrient on the anaerobic digestion stability of food waste (FW) were investigated under mesophilic conditions with the aim of avoiding volatile fatty acids accumulation, and inorganic elements deficiency. When LMP concentration ranged from 6.0 to 10g/L, the FW anaerobic digestion could maintain efficient and stable state. These advantages are attributed to the existence of Ca, Na, Mg, K, Fe, and alkaline substances that favor the methanogenic process. The highest CH4 yield of 272.8mL/g-VS was obtained at LMP and VS concentrations of 10.0 and 19.8g/L, respectively, with the corresponding lag-phase time of 3.84d and final pH of 8.4. The methanogens from residue digestates mainly consisted of Methanobrevibacter, coccus-type and sarcina-type methanogens with LMP addition compared to Methanobacteria in control. However, higher concentration of LMP inhibited methanogenic activities and methane production.

Effect of Supplementing TMR Diets with Artificial Saliva and Acid Buf on Optimizing Ruminal pH and Fermentation Activity in Cows

Abstract The objective of the study was to determine the effect of adding buffering agents to a total mixed ration (TMR) on the pH and on the VFA, lactic acid and NH3-N content of rumen fluid. The experiment was carried out with three nonproductive cows fitted with permanent rumen fistulas in a 3×3 Latin square design with two stages differing in the amount of added buffer (50 g/day in stage I or 100 g/day in stage II). The control diet (C) contained no buffering agent. The AB experimental diet was supplemented with Acid Buf (Noack Polen Ltd.) containing calcium carbonate, major and trace elements, and the AS experimental diet was supplemented with our own produced artificial saliva powder containing a mixture of chemical compounds (NaHCO3, KCl, CaCl2, Na2HO4·12H2O, NaCl, MgSO4·7H2O) in the appropriate proportions (McDougall, 1948), combined with wheat bran at a 1:1 ratio. The preparations were added to the concentrate mixture in TMR which contained (% DM): maize silage, 29.9; wilted grass silage, 17.4; ensiled brewers’ grains, 2.4; barley straw, 10.3; and concentrate mixture, 40.0. Samples of rumen fluid collected before feeding (0 h) and after feeding (2, 4, 6 and 8 h) were analysed for pH, and the samples collected 4 h postprandial were analysed for VFA, lactic acid and NH3-N. The artificial saliva added at 100 g/day to the mixture of chemical compounds (without a carrier) contributed to a significant (P≤0.01) increase in rumen fluid pH at 4 h compared to cows receiving diets C and AB. In both stages of the experiment, cows receiving the buffering agents tended to achieve higher pH values in the other hours of the test compared to group C. In the collected samples of rumen fluid, no significant (P>0.05) differences were observed among the cows in VFA and total VFA, in C2/C3 and C3/C4 acid ratios, and in NH3-N content. Neither did the type and amount of buffers had a significant effect on the percentage ratios of selected fatty acids (acetic, propionic and butyric) in total VFA. No presence of lactic acid was detected in the analysed samples of rumen fluid. It can be stated that when the total mixed ration is properly balanced, the type and amount of buffers have no significant effect on changes in the rumen fermentation activity of cows.

Effect of banana flower powder supplementation as a rumen buffer on rumen fermentation efficiency and nutrient digestibility in dairy steers fed a high-concentrate diet

Four rumen-fistulated dairy steers, two and a half year old with liveweight of 220±15.0kg, were randomly assigned according to a 4×4 Latin square design to study the effect of banana flower powder (BAFLOP) supplementation as a rumen buffering agent on ruminal pH, nutrient digestibility and rumen fermentation fed a high-concentrate diet. The four dietary treatments were BAFLOP supplementation at 0, 10, 20 and 30g/kg of dry matter intake (DMI), respectively. During the experimental periods, all steers were fed a diet containing roughage to concentrate ratio of 30:70 at 20g DMI/kg of body weight and rice straw was used as a roughage source. Based on the present study, the results revealed that dry matter, organic matter and crude protein digestibilities were not affected (P>0.05) by BAFLOP supplementation, whereas digestibilities of neutral detergent fiber and acid detergent fiber increased with the increasing levels of BAFLOP supplementation (P<0.05). It was also found that total nitrogen (N) intakes were similar among treatments. However, fecal N excretions decreased with the increasing levels of BAFLOP supplementation, while urinary N excretions were similar among treatments. BAFLOP supplementation increased N balance both absorption and retention (P<0.05). Moreover, purine derivative absorption and microbial protein synthesis were increased by BAFLOP supplementation, whereas efficiency of microbial nitrogen supply (EMNS) and microbial nitrogen supply were similar among treatments. In addition, ruminal temperature, ammonia nitrogen, and blood urea nitrogen were not influenced by BAFLOP supplementation, whilst ruminal pH enhanced (P<0.05) in steers supplemented with BAFLOP at 20 and 30g/kg of DMI. The concentration of total volatile fatty acid and acetic acid increased with BAFLOP supplementation, whereas propionic and butyric acid remained the same. The present findings showed that BAFLOP supplementation enhanced total bacterial, protozoal, and cellulolytic bacterial growth, while numbers of fungal zoospores, amylolytic and proteolytic bacteria were similar among treatments. In conclusion, BAFLOP supplementation improved rumen ecology and nutrient digestibility by enhancing ruminal pH, nitrogen utilization, EMNS and ruminal microbial population. This study suggested that BAFLOP could be supplemented as a rumen buffering agent at 20–30g/kg of DMI.

Removing polysaccharides-and saccharides-related coloring impurities in alkyl polyglycosides by bleaching with the H2O2/TAED/NaHCO3 system

The effect of H2O2/TAED/NaHCO3 system, namely NaHCO3 as alkaline agent with the (tetra acetyl ethylene diamine (TAED)) TAED-activated peroxide system, bleaching of alkyl polyglycosides solution was studied by spectrophotometry. The results showed that the optimal bleaching conditions about H2O2/TAED/NaHCO3 system bleaching of alkyl polyglycosides solution were as follows: molar ratio of TAED to H2O2 was 0.06, addition of H2O2 was 8.6%, addition of NaHCO3 was 3.2%, bleaching temperature of 50–65°C, addition of MgO was 0.13%, and bleaching time was 8h. If too much amount of NaHCO3 was added to the system and maintained alkaline pH, the bleaching effect would be greatly reduced. Fixing molar ratio of TAED to H2O2 and increasing the amount of H2O2 were beneficial to improve the whiteness of alkyl polyglycosides, but adding too much amount of H2O2 would reduce the transparency. In the TAED-activated peroxide system, NaHCO3 as alkaline agent and buffer agent, could overcome the disadvantage of producing black precipitates when NaOH as alkaline agent.

Differential effect of buffering agents on the crystallization of gemcitabine hydrochloride in frozen solutions.

The purpose of this study was to evaluate the differential effect of buffering agents on the crystallization of gemcitabine hydrochloride (GHCl) in frozen solutions. Four buffering agents, viz. citric acid (CA), malic acid (MA), succinic acid (SA) and tartaric acid (TA) were selected and their effect on GHCl crystallization was monitored using standard DSC and low temperature XRD. Onset of GHCl crystallization during heating run in DSC was measured to compare the differential effect of buffering agents. Glass transition temperature (Tg'), unfrozen water content in the freeze concentrate and crystallization propensity of the buffering agents was also determined for mechanistic understanding of the underlying effects. CA and MA inhibited while SA facilitated crystallization of GHCl even at 25 mM concentration. Increasing the concentration enhanced their effect. However, TA inhibited GHCl crystallization at concentrations <100mM and facilitated it at concentrations ≥100 mM. Lyophilization of GHCl with either SA or TA yielded elegant cakes, while CA and MA caused collapse. Tg' failed to explain the inhibitory effects of CA, MA and TA as all buffering agents lowered the Tg' of the system. Differential effect of buffering agents on GHCl crystallization could be explained by consideration of two opposing factors: (i) their own crystallization tendency and (ii) unfrozen water content in the freeze concentrate. In conclusion, it was established that API crystallization in frozen solution is affected by the type and concentration of the buffering agents.

Photocatalytic nitrate reduction over Pd–Cu/TiO2

Abstract The extension of photocatalytic nitrate reduction in water by a 1%Pd–1%Cu (%wt) catalyst supported on TiO 2 was evaluated under different reaction conditions. A series of electron sacrificial donors such as formic acid, oxalic acid, ethanol, methanol, and humic acid were used for inhibiting the mechanism of electron/hole recombination on the semiconductor by hole scavenging. In addition, the roles of H 2 as reducing agent and CO 2 as buffer are also discussed. The photocatalytic process is found to be more selective towards nitrogen than the dark catalytic process. Hole scavengers, or reducing H 2 increase significantly the photocatalytic reduction of nitrate. Complete (100%) conversion was obtained when both H 2 and CO 2 were used as reducing and buffer agent, respectively. Among the hole scavengers tested, 0.08 M formic acid solution represents the best compromise between nitrate conversion (84%) and nitrogen selectivity (83%).