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Abstract: There is an urgent need for a biorelevant antioxidant capacity assay, which is crucial to quality-assured polyphenol dietary supplements. We hypothesize that the 'position', more than the 'number' of phenolic groups, is critical to the antioxidant capacity of polyphenols. Computational Antioxidant Capacity Simulation (CAOCS) assay was implemented to test the hypothesis, while refinement of existing assay protocol was aimed at reducing the cost of analysis. The antioxidant capacities of resorcinol, catechol and hydroquinone (3 diphenol positional isomers) were determined by CAOCS assay. Photometric titration experiments and associated informatics that constitute CAOCS assay were evaluated through the use of small increments (< 1 mL) of antioxidant solution. Antioxidant capacity ranking of the positional isomers was found to be; hydroquinone > catechol > resorcinol, (60/g, 46/g and 28/g respectively). The relative bond strength of the phenolic groups, which governs the ranking, was accounted for by structural theory. Optimal 250 µL increment of antioxidant solution afforded a 75% reduction of the amount of antioxidant required in the original assay protocol, where a 1 mL increment was used. CAOCS values vary widely for the positional isomers. The unique structure-antioxidant capacity-correlation (SACC) which confirmed our hypothesis is a signature of biorelevance. Significantly, microliter increments reduced the amount of active material required and hence, the cost of analysis. The methodology is thus attractive for profiling exotic and more expensive polyphenols. CAOCS assay holds a great promise of enabling quality-by-design (QbD) of polyphenol dietary supplements. Keywords: Diphenol positional isomers, antioxidant capacity, photometric titration, model fitting, hydroquinone, biorelevant assay.Download Full Article |
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Abstract: Response surface methodology was applied for optimizing indigo carmine (IC) dye removal by electrochemically produced ferrate (VI). Box-Behnken design was employed in this study, and design parameters were pH, Fe (VI) dose and initial dye concentration (Co). R2 and adjusted R2 values were very high that indicated very good accuracy for the employed model. Optimum operational conditions were: 4.08-7.69 for pH, 24-118.83 mg/L for Fe (VI) dose and 60.68-99.13 mg/L for complete removal of IC. Produced by electrochemical method Ferrate (VI) provides high effectiveness for IC dye-containing synthetic wastewater. Keyword: Adsorption, modified activated carbon, rare earth elements (REEs), adsorption isotherms, kinetics. |
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Abstract: The special geometry of the steroid skeleton causes formation of bile acid anion micelles with small aggregation numbers, in contrast to aliphatic amphiphiles. Relative to the tendency to reduce membrane toxicity, pharmacological investigations of bile acids are mainly concerned with their oxo derivatives. Since micelles of these bile acids have been insufficiently studied, the objective of this work is the determination of aggregation numbers of corresponding micelle monomers. The aggregation numbers were determined using the freezing point depression of the solutions by applying the appropriate equations of Debye-Hückel, Guggenheim and Gibbs-Duhems, and using pNa data measured with a Na-selective electrode. Depending on the structure of the bile acid anion, the values obtained for the aggregation numbers were in the range from 2.09 to 3.44. The increase in number of oxo groups in the molecule is accompanied by a decrease in hydrophobicity of the convex side of the steroid skeleton of the bile acid anion, resulting in a lower aggregation number. Keywords: Micelles, bile salts, aggregation number, steroid skeleton, critical micellar concentration.Download Full Article |
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Abstract: The density data for the binary mixtures of an ionic liquid (IL), 1-ethyl-3-methylimidazolium diethylphosphate [EMIM][DEP], and water (methanol or ethanol) were measured at 1 atm as a function of composition in the temperature range of (293.15 to 333.15) K using a vibrating-tube densimeter. The excess molar volumes (VE) and other thermodynamic properties were derived from the density data. All VE values are negative for the binary mixtures in the whole composition range, and reach to the maximum at the mole fraction of IL of ca. 0.3. The VE values decrease with increasing temperature for the aqueous solution of ILs, but increase with the increasing temperature for the IL solutions of methanol or ethanol. The excess molar volumes were correlated successfully by an empirical equation with the maximum average absolute relative deviation within 0.02%. Keywords: Density, excess volume, ionic liquid, water, methanol, ethanol.Download Full Article |
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Abstract: Ion-pair formation constants (KMA0) for MA+ = MPic+ and MCl+ in water were determined at 298 K and ionic strength → 0 by extraction experiments of picric acid (HPic) in the presence of M(II) in the water phase into benzene (Bz) and by potentiometry with a commercial Cl--selective electrode, respectively. Here, M denotes Ca(II), Sr(II), Ba(II), Cu(II), and Cd(II). In adding Pb(II) data, a relation between KMA0 values was KMCl0<KMPic0 for a given M(II).For CdPic+, the KMA0 value (= 136mol-1 dm3) determined by the HPic extraction was somewhat larger than that (= 108) potentiometrically-determined before with a Cd2+-selective electrode, while for CaPic+ the former value (= 89) equaled the latter one (= 88) determined before with a Ca2+-selective electrode. Keywords: Ion-pair formation constants, extraction, potentiometry, divalent metal ions, picrates, chlorides.Download Full Article |
