Ionic Liquids as Efficient Extractants for Quercetin from Red Onion (Allium cepa L.) - Pages 21-38

Urszula Domańska, Anna Wiśniewska, Zbigniew Dąbrowski and Mikołaj Więckowski

DOI: https://doi.org/10.6000/1929-5030.2018.07.04

Published: 06 November 2018

Abstract: The solubility of Quercetin in alcohols, esters and in 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA] ionic liquid (IL) using the dynamic method was measured at constant pH in a range of temperature 233-373 K and compare to the literature data. The experimental solubility data have been correlated by means of commonly known G^E models,UNIQUAC and NRTL with the assumption that the systems studied here present simple eutectic behaviour. The basic thermal properties of Quercetin, i.e., fusion temperature and the enthalpy of fusion have been measured with differential scanning microcalorimetry technique (DSC).The application of alcohols, esters and ionic liquids (ILs) as alternatives to conventional organic solvents in the liquid-liquid extraction of Quercetin from different medicinal plants, flowers and frozen red onion (Allium cepa L.) was investigated. The parameters affecting the extraction yield using ILs such as chemical structures of the IL cation and anion, the phase volume ratio of extracting solvent, time of extraction and the Quercetin form of sample and concentration were evaluated. Specific Quercetin composition was performed through HPLC measurements. Using the most effective ILs in extraction, the 14.3±0.1g∙kg^-1 and 5.9±0.1 g∙kg^-1of Quercetin from frozen pure red onion was obtained with N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, [N_2,2,1,2OCH3][BF₄] and 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA], respectively.

Keywords: Quercetin, Ionic liquids, Solubility, Extraction from red onion, Hydrogen bonding interaction.

Abstract: This study aims at extending the general methodology for the study of predominance and reactivity of ionic homogeneous solutions to precipitation reactions. This extension was satisfactorily formulated by the definition of the fraction of species concept in heterogeneous systems for the first time. An easy form to fully integrate the ion product concept with other descriptions of homogeneous ionic reactions, to obtain predominance zone diagrams (PDZ), to enrich the use logarithmic relative diagrams, to generate continuous equations from titration curves, and to generalize side-reaction coefficients to heterogeneous systems using easy-to-compute algorithms of calculation is shown.

The new representation was applied in a study case exemplified by the hydrolysis of copper (II) in the absence and the presence of complexing ligands considering soluble and insoluble species of the metal ion. The results perfectly compare to those obtained by established numerical and graphical methods of analysis of solution equilibria showing the equivalence among the different descriptions.

Pre-nucleation clusters (PNCs) theory of precipitation reactions was used as a mean to interpret the theoretical implication that this view engendered.

Keywords: Distribution fraction diagram, predominance zone diagram, precipitation reactions, side-reaction coefficients, modeling precipitation reactions.

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Abstract: The influence of low-frequency sonolysis on the kinetics of liquid-phase bimolecular liquid-phase reactions was studied by mathematical modeling with due regard for the association of starting reagents into dimers and trimers. With increasing frequency and amplitude of low-frequency sonic waves (up to some critical value), we observed the disappearance of trimers and concomitant cessation of the reaction. This observation offers an additional tool for controlling reaction rate by the external action of low-frequency vibrations.

Keywords: Chemical reaction, Kinetics, Liquid medium, Reagent association, Low-frequency action.

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Abstract: The integral toxicity of solutions of a number of carboxylic acids was estimated by measuring their chemical oxygen consumption (COC) and the biochemical oxygen demand for the biodegradation of substances due to microorganisms (BOD₅). The analytical dependences of COC and BOD₅ as well as of their ratio for these compounds on concentration were determined. The values of COC and BOD₅ for a number of acid solution mixtures were measured. The coefficient that indicates biodegradability of substances has been calculated. The chemical consumption of oxygen by solutions of organic acids is shown to increase with the transition from lower to higher homologues and with increase in the concentration of the solution.

The kinetics and degree of removal of organic acids out of solutions due to sorption on the clay-like mineral, glauconite, have been studied. Glauconite that is the natural sorbent is characterized by a high adsorbing power in solutions of organic acids under both stationary and non-stationary conditions. However, adsorption becomes complicated as complexity of the organic acid molecule structure grows. To achieve more comprehensive removal of acids out of solutions, one reduces flow rate and increases thickness of the sorbent layer.

Keywords: Organic acids, biodegradability, oxygen consumption, sorption, glauconite.

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Abstract: In this research, the adsorption of Cu2+ ions from aqueous solution was investigated by the modified poly (ethylene terephthalate) fibers as a new adsorbent. The best condition of electrospinning was recorded (voltage= 10 kV – distance from nozzle= 12.5 cm – solution convcentration= 0.2 g/mL). The optimum condition for removal of Cu2+ ions were determined (pH=10 – time= 60 min - C= 120 mg/L, qm = 62.4 mg/g). The adsorption data were best fitted by dubinin-radushkevich isotherm and pseudo-second order kinetic models, as well. Structure of the nanofibers were emphasized by scanning electron microscpy (SEM) and thermo gravimetric analysis (TGA).

Keywords: Nanofibers, Adsorption, Isotherm, Kinetics.