Solubility of high-value compounds in ethyl lactate: Measurements and modeling

Abstract

Solid-liquid equilibria of binary mixtures containing high-value compounds and ethyl lactate were studied. Using the gravimetric method, the solubility of various solutes such as caffeine, vanillic acid, ferulic acid, caffeic acid and thymol in ethyl lactate was measured as a function of temperature (temperature range of 298.2 -343.2 K), at atmospheric pressure. The differences in solubility of a given solute in water-saturated and dry ethyl lactate were observed. The deviation of these binary systems from ideal mixture behaviour was discussed.In order to understand the solubilization process, melting properties of pure solutes were determined by differential scanning calorimetry (DSC). The obtained solubility data were represented using UNIQUAC and UNIFAC-based models as well as with the Cubic-Plus-Association (CPA) equation of state. The results of the modeling indicate that these models are the appropriate tools for representing the solubility behaviour of various solutes in ethyl lactate. association equation of state * Maximal standard uncertainties u are u(Tm) = 0.28 K, u(ΔH fus ) = 0.6, u(ΔC p ) = 6.4. a Solid-solid transition of caffeine b Calculated using a group contribution method as described elsewhere [25]. c Calculated using a group contribution method for the estimation of the heat capacities of liquids [38] and the power-law method to estimate heat capacities of organic solids [39].

Effect of cosolvents (ethyl lactate, ethyl acetate and ethanol) on the supercritical CO 2 extraction of caffeine from green tea

“…For comparison, the estimated caffeine solubility in pure CO 2 was 0.029 % mass, which is quite in agreement with the experimental solubility measured at 343 K and 28.1 MPa (0.023 % mass) [35]. These estimated solubilities presume that, as in the case of the solubility of caffeine in the liquid solvents [30,31], the solubility of caffeine in CO 2 with ethyl lactate cosolvent is higher than in the case of ethanol or ethyl acetate cosolvents.…”

“…The solubility of caffeine in ethyl lactate at 323 K is 5.1 % mass [30], while solubility in ethanol and ethyl acetate at the same temperature is, respectively, 2.3 % and 2.2 % mass [31].…”

“…For example, Park et al. [17,18] studied the decaffeination of green tea using CO 2 and ethanol as cosolvent at 30 MPa and 343 K, attaining a recovery of caffeine around 92-96 %. In another contribution [19], the authors employed the same extraction conditions with pure CO 2 and water as cosolvent and caffeine recoveries were lower.…”

Pressurized liquid extraction of caffeine and catechins from green tea leaves using ethyl lactate, water and ethyl lactate + water mixtures

“…Previous data available in the literature about the solubility of caffeine in water corresponds to values of 2.2% mass at 298 K (Bustamante et al, 2002). On the other side, the solubility of caffeine in ethyl lactate was previously reported by the authors (Manic et al, 2012) resulting in 3.2% mass at 303 K. Thus, previous data from the literature satisfactory agree with the solubilities measured in this work (2.0 and 3.0% mass at 298 K for, respectively, water and ethyl lactate). The values given in Table 2 correspond to the average value (x) of experiments carried out by duplicate.…”

Solutions of ionic liquids with diverse aliphatic and aromatic solutes – Phase behavior and potentials for applications: A review article

“…High-value compounds: thymol, ferulic acid, caffeic acid, vanillic acid and caffeine represent compounds with important positive health effects -anti-cancer, anti-sickling and anthelmintic as well as potential helpful neurological impacts (Manic et al, 2012). Consequently, there is an ever growing necessity to search for alternative solvents which would allow sustainable extraction of these compounds from their natural matrices.…”