SciCombinator

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Concept: Aqueous solution

28

Probe electrospray ionization (PESI) is a recently developed method that uses a sharp solid needle as electrospray emitter and the sample is loaded to the needle tip by repetitive movement of the needle probe. This method has been previously used for the analysis of sample with high salt concentration and real-world samples without sample pretreatment. Although PESI is also applicable to aqueous solution, the ion signal stability and reproducibility were not satisfactory due to the spontaneous occurrence of corona discharge taking place on the metallic needle tip.

Concepts: Concentration, Chemical properties, Chemistry, Solid, 1980s music groups, Ion source, Solutions, Aqueous solution

28

The effects of monorhamnolipid (RL-F1) and dirhamnolipid (RL-F2) on the sorption and desorption of triclosan (TCS) in sediment-water system were investigated in this study. Results of the bath equilibrium experiments showed that RL-F2 provided much higher solubilization enhancement for TCS than RL-F1. Sorption of both rhamnolipids by the sediments was highly correlated with the sediment clay content. Moreover, the apparent distribution coefficients of TCS K(d)(∗) decreased with the increase of rhamnolipid concentration (0.05-7.5mM), and RL-F2 presented a larger distribution capacity of TCS into the aqueous phase at relatively higher concentrations (>2.5mM). Further results also indicated that the release of TCS from sediment could be enhanced by both rhamnolipids. RL-F2 was more efficient than RL-F1 in desorbing TCS from the sediment with low clay content. The TCS desorption percentages R(d)(∗) of RL-F2 (5mM) was 1.8-2.4 times that of RL-F1. These findings could provide useful guidelines for the application of rhamnolipid-enhanced remediation technologies for TCS contaminated sediment.

Concepts: Concentration, Chemistry, Erosion, Aqueous solution, Silt, Phase diagram, Parts-per notation, Sediments

28

A novel layered double hydroxide containing lanthanum (Cu/Mg/Fe/La-LDH) has been synthesized and used for the removal of arsenate from aqueous solutions. The purpose of incorporation of La(3+) into LDHs was tried to enhance the uptake efficiency of arsenate and broaden the application field of LDHs functional materials. Effects of various physico-chemical factors such as solution pH, adsorbent dosage, contact time and initial arsenate concentrations on the adsorption of arsenate onto Cu/Mg/Fe/La-LDH were investigated. Results showed that the removal efficiency of arsenate increased with the increment of the lanthanum content in Cu/Mg/Fe/La-LDH adsorbents, and the optimized lanthanum content was 20% of the total trivalent metals composition (Fe(3+) and La(3+)). The adsorption isotherms can be well described by Langmuir equation, and the adsorption kinetics of arsenate followed the pseudo-second-order kinetic model. Coexistent ions such as HPO(4)(2-), CO(3)(2-), SO(4)(2-), Cl(-) and NO(3)(-) exhibited obvious competition with arsenate for the adsorption on Cu/Mg/Fe/La-LDH. The solution pH significantly affected the removal efficiency, which was closely related to the change of arsenate species distribution under different pH conditions. The predominant adsorption mechanism can be mainly attributed to the processes including ion exchange and layer ligand exchange.

Concepts: Concentration, Chemical properties, Chemistry, Adsorption, Solutions, Aqueous solution, Solution, Langmuir equation

28

Sustained release aqueous eye drops of dexamethasone, based on cyclodextrin (CD) nanogels, were designed and tested in vivo. γCD units were cross-linked in the form of nanogels by means of an emulsification/solvent evaporation process. The composition of the nanogels was optimized with regard to drug loading and release rate. The eye drops consisted of an aqueous solution of dexamethasone in 2-hydroxypropyl-γ-cyclodextrin (HPγCD) medium containing γCD nanogels. The nanogel eye drops (containing 25mg dexamethasone per ml) were tested in rabbits and compared to the commercially available product Maxidex(®) (suspension with 1mg dexamethasone per ml). One drop administration of the nanogel eye drops resulted in nearly constant dexamethasone concentration for at least 6hours in the tear fluid (mean concentration±SD=295±59μg/ml) whereas the concentration after administration of Maxidex(®) fell rapidly from 9.72±3.45 one hour after application to 3.76±3.26μg/ml three hours after application. The maximum dexamethasone concentration in the aqueous humor (twohours after application) was 136±24mg/ml after application of the nanogel eye drops, and only 44.4±7.8μg/ml after application of Maxidex(®). The dexamethasone nanogel eye drops were well tolerated with no macroscopic signs of irritation, redness or other toxic effects.

Concepts: Concentration, Chemical properties, Chemistry, Eye, Solutions, Aqueous solution, Solution, Aqueous humour

27

In this study, natural Akadama clay was used for Cr (VI) removal from aqueous solution. Batch experiments were carried out to investigate the effect of contact time, initial pH, and adsorbent dose on Cr (VI) adsorption. Results showed that Cr (VI) adsorption on natural Akadama clay reached equilibrium in 180min. The Cr (VI) removal efficiency of 46.8% without pH adjustment increased to 73.8% at the optimum initial pH of 2. The maximum adsorption capacity was 4.29mgg at an initial concentration of 50.0mgL and adsorbent dosage of 5gL. The equilibrium data fitted Freundlich isotherm better than Langmuir isotherm, and they were well explained by pseudo-second-order kinetic model. Adsorption mechanism analysis proved that electrostatic adsorption dominated during the removal process. Results from this study demonstrate that natural Akadama clay has the potential to be an efficient adsorbent for Cr (VI) adsorption compared to other natural mineral adsorbents.

Concepts: Concentration, Chemical properties, Chemistry, Adsorption, Solutions, Aqueous solution, Freundlich equation, Langmuir equation

27

This work describes the preparation and evaluation of mucoadhesive microspheres, using Abelmoschus esculentus polysaccharide as a novel carrier for safe and effective delivery of rizatriptan benzoate into nasal cavity. The polysaccharide was extracted from the fruit of A. esculentus and mucoadhesive microspheres were prepared by emulsification, followed by crosslinking using epichlorohydrin. Prepared microspheres were evaluated for size, morphology, swelling properties, mucoadhesive strength, encapsulation efficiency and drug release. Microspheres were found to release 50% of drug within 15 min and rest of the drug was released within 60 min. The drug release was found to decrease with increasing concentration of polysaccharide. To determine the retention time of the microspheres in the nasal cavity of rabbits, the microspheres were radiolabelled with (99m)Tc and subjected to gamma scintigraphy. The results showed a significant improvement in the nasal retention of the microspheres as compared to the aqueous solution of radiolabelled free-drug.

Concepts: Nuclear medicine, Concentration, Chemistry, Solutions, Aqueous solution, Okra

26

Glycerol is selectively converted to hydroxyacetaldehyde (HAA) and H2 in aqueous solution on TiO2-based photocatalysts. The product selectivity was verified to be strongly dependent on the facets of TiO2. Rutile with high percentage of {110} facets results in over 90% superior selectivity of HAA, while anatase with {001} or {101} facets gives only 16% and 49% selectivity for HAA, respectively.

Concepts: Concentration, Chemistry, Titanium dioxide, Solutions, Aqueous solution, Rutile, Photocatalysis, Anatase

24

Amphiphilic block copolypeptoids consisting of a hydrophilic poly(N-ethyl glycine) segment and a hydrophobic poly[(N-propargyl glycine)-r-(N-decyl glycine)] random copolymer segment [PNEG-b-P(NPgG-r-NDG), EPgD] have been synthesized by sequential primary amine-initiated ring-opening polymerization (ROP) of the corresponding N-alkyl N-carboxyanhydride monomers. The block copolypeptoids form micelles in water and the micellar core can be cross-linked with a disulfide-containing diazide crosslinker by copper-mediated alkyne-azide cycloaddition (CuAAC) in aqueous solution. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis revealed the formation of spherical micelles with uniform size for both the core-crosslinked micelles (CCLMs) and non-crosslinked micelles (NCLMs) precursors for selective block copolypeptoid polymers. The CCLMs exhibited increased dimensional stability relative to the NCLMs in DMF, a non-selective solvent for the core and corona segments. Micellar dissociation of CCLMs can be induced upon addition of a reducing agent (e.g., dithiothreitol) in dilute aqueous solutions, as verified by a combination of fluorescence spectroscopy, size exclusion chromatography (SEC) and 1H NMR spectroscopic measurement. Doxorubicin (DOX), an anti-cancer drug, can be loaded into the hydrophobic core of CCLMs with a maximal 23% drug loading capacity (DLC) and 37% drug loading efficiency (DLE). In vitro DOX release from the CCLMs can be triggered by DTT (10 mM), in contrast to significantly reduced DOX release in the absence of DTT, attesting to the reductively responsive characteristic of the CCLMs. While the CCLMs exhibited minimal cytotoxicity towards HepG2 cancer cells, DOX-loaded CCLMs inhibited the proliferation of the HepG2 cancer cells in a concentration and time dependent manner, suggesting the controlled release of DOX from the DOX-loaded CCLMS in the cellular environment.

Concepts: Spectroscopy, Chemotherapy, Concentration, Chemical properties, Chemistry, Polymer, Polymer chemistry, Aqueous solution

23

This study evaluates the effect of modified lecithin (ML) and sodium caseinate (SC) on the formulation, stability and bioaccessibility of astaxanthin (AXT) loaded oil-in-water (O/W) nanoemulsions. These nanoemulsions were formulated using high-pressure homogenization in four passes at 100MPa. The volume mean diameter (d4,3) of nanoemulsions produced by ML and SC were 163±5 and 144±12 nm, respectively. The physiochemical stability of nanoemulsions was recorded at 25°C. The nanoemulsions prepared by ML were stable for 30 minutes against a wide range of pH and heating temperatures (60-120 °C). However, ML-stabilized nanoemulsions showed droplet growth when treated at high NaCl concentrations. In comparison, droplet growth was observed in SC-stabilized nanoemulsions at pH4 and at high temperature treatment. However, SC-stabilized nanoemulsions were stable at high NaCl concentration (500 mM). The SC-stabilized nanoemulsions showed good physical and chemical stability (>70%) after 30 days of storage. The bioaccessibility of AXT in nanoemulsions was significantly higher in ML (33%) than in SC-stabilized nanoemulsions (6%), indicating a strong influence of emulsifier on bioaccessibility. These findings provide valuable information in designing nutritional products such as aqueous based AXT fortified beverages.

Concepts: Concentration, Chemistry, Temperature, Thermodynamics, Heat, Trigraph, Materials science, Aqueous solution

22

The sonochemiluminescence spectra of electron-excited ions*[Ru(bpy)3]2+was registered for the first time during sonolysis of argon saturated aqueous solutions of Ru(bpy)3Cl2with low concentration. At single-bubble sonolysis, the luminescence band of ruthenium is recorded at a concentration of Ru(bpy)3Cl2from 10-6 M, and at multibubble from 10-5 M. Possible mechanisms for the appearance of the band of a tris-bipyridyl ruthenium(II) complex on the background of an structureless continuum of water in the spectra of sonoluminescence are analyzed. Based on the results of the comparison of the sonoluminescence spectra of Ru(bpy)3Cl2aqueous solutions with the sonoluminescence spectra of aqueous solutions of rhodamine B (which has a high quantum yield of photoluminescence) it was established that a possible mechanism of sonophotoluminescence does not play a decisive role in ruthenium sonoluminescence. The effect of radical acceptors (O2, C2H5OH, Cd2+, I-) on ruthenium sonoluminescence is analyzed. The most significant mechanism for the formation of electron-excited ions*[Ru(bpy)3]2+during sonolysis is the sonochemiluminescence in oxidation-reduction reactions involving [Ru(bpy)3]2+ions and radical products of sonolysis of water (OH, H, e-aq) in the solution volume.

Concepts: Concentration, Chemical properties, Chemistry, Luminescence, Solutions, Aqueous solution, Solution, Sonoluminescence