Browsing by Author "Soares, Bruna de Paula"
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- Glycerol ethers as hydrotropes and their use to enhance the solubility of phenolic acids in waterPublication . Soares, Bruna de Paula; Abranches, Dinis O.; Sintra, Tânia E.; Leal-Duaso, Alejandro; García, José Ignacio; Pires, Elísabet; Shimizu, Seishi; Pinho, Simão; Coutinho, João A.P.The use of glycerol ethers (with alkyl side chain ranging from one to six methyl groups) as hydrotropes to enhance the solubility of gallic and syringic acids in water was here studied. These compounds were selected due to their biological and industrial applications and for serving as model molecules for lignin solubilization. The results obtained were compared against traditional co-solvents, demonstrating the exceptional hydrotropic ability of glycerol ethers. Setschenow constants show that the hydrophobicities of both solute and hydrotrope play an important role in the solubility enhancement by hydrotropy, shedding light into its molecular mechanism. The solubility curves of gallic acid and syringic acid in the aqueous glycerol ether solutions were fitted using a recently proposed statistical thermodynamics-based model. This allowed the estimation of solute recovery from hydrotropic solution by using water as antisolvent. Unlike what is usually claimed it is here shown that in some conditions it is impossible to recover the solute by simply adding water. This analysis paves the way for a rational design and selection of hydrotropes, in which both solubility enhancement and solute recovery are critical parameters to be taken into account.
- Juçara fruit (Euterpe Edulis Martius) valorization combining emergent extraction technologies and aqueous solutions of alkanediolsPublication . Soares, Bruna de Paula; Ferreira, Ana M.; Justi, Marina; Rodrigues, Luiz G.G.; Oliveira, José V.; Pinho, Simão; Coutinho, João A.P.Anthocyanins from juçara fruits were extracted by pressurized liquid extraction (PLE) or ultrasound-assisted extraction (UAE), using aqueous solutions of 1,2-alkanediols and glycerol ethers as biobased solvents. The PLE (100 bar, 13 min, 1 mL/min flow rate) in the optimal extraction conditions originated 23.1 mganthocyanins gdry biomass -1. On the other hand, the UAE was 10 min long, and the optimal conditions using 1,2-propanediol were 42.6 wt%, 160 W, and pH 7.0, leading to 50 mganthocyanins gdry biomass 1. Extractions at the UAE optimized conditions, with aqueous solutions of five different 1,2-alkanediols and three glycerol ethers were performed, and compared to water and ethanolic extracts. The biobased solvent solutions presented anthocyanin yields up to 33% higher than water, and were shown to be as efficient as ethanol/water, but generated extracts with higher antioxidant capacity. The anthocyanin-rich extract of juçara, obtained with 1,2-propanediol, was used in the production of a natural soap and incorporated into a cream, showing that the addition of the juçara extract resulted in an antioxidant capacity in both products.
- Medições de solubilidade de compostos pouco solúveis em águaPublication . Soares, Bruna de Paula; Pinho, Simão; Ferreira, Olga; Leite, Priscilla dos Santos GaschiO estudo da solubilidade de compostos pouco solúveis em líquidos reveste-se de grande importância em diversos contextos nas áreas farmacêutica, alimentar ou ambiental. Na área ambiental, a solubilidade de pesticidas em água é um parâmetro relevante na avaliação do seu impacto ambiental e no desenvolvimento de alternativas de descontaminação. Neste contexto, o principal objetivo deste trabalho foi a implementação de uma metodologia experimental para medição de solubilidades de compostos pouco solúveis em água aplicando uma variante do método analítico do frasco agitado, com membranas de diálise. Primeiramente, validou-se a metodologia utilizando o bifenilo como composto modelo. Depois, mediu-se a solubilidade aquosa de cinco pesticidas (carbaril, difenamida, diuron, propaclor e propanil) a 25 e 40 °C, obtendo-se em geral resultados consistentes com a escassa informação disponível na literatura. Na área farmacêutica, o aumento da solubilidade de compostos pouco solúveis em água poderá ser alcançado, por exemplo, através da adição de solventes orgânicos ou de ciclodextrinas que promovam a formação de complexos solúveis em água. Neste trabalho, o composto escolhido foi um ácido fenólico, o ácido trans-cinâmico, com diversas atividades biológicas e farmacêuticas. Assim, mediu-se a solubilidade deste ácido em solventes mistos água + metanol e água + etanol, a 25 °C. Verificou-se um aumento da solubilidade do ácido trans-cinâmico de 27,5 vezes em metanol puro e 162 vezes em etanol puro. De forma complementar, os estudos preliminares de complexação com α- ciclodextrina realizados, permitiram demonstrar que a solubilidade aumentou até 7,4 vezes, com um diagrama de fases de solubilidade do tipo B
- Solubility studies of trans-cinnamic acid in mixed solventsPublication . Soares, Bruna de Paula; Ferreira, Olga; Leite, Priscilla G.; Pinho, SimãoPhenolic acids are a subclass of phenolic compounds with chemical and biological properties of interest in the pharmaceutical and food industries. The design of their extraction and separation processes includes the knowledge of their thermophysical properties as well as multicomponent solid-liquid equilibria data. For these compounds, even essential solubility data in pure organic solvents and water are scarce. Therefore, in this work, trans-cinnamic acid was chosen as a model compound for which only a few solubility data in pure water and alcohols can be found in the literature [1-3]. The solubility of trans-cinnamic acid in the mixed solvents water + ethanol, and water + methanol was measured, at 298.15 K, using the isothermal shake-flask method and quantitative analysis either by gravimetry or UV spectrophotometry. As can be seen in Fig. 1, the solubility of the acid can significantly increase with the addition of the alcohol, with a more pronounced effect induced by ethanol. In a complementary approach and aiming to search for other methods to increase the aqueous solubility of trans-cinnamic acid, the phase-solubility diagram was determined for systems containing α-cyclodextrin. References [1] J. Li, Z. Zeng, L. Sun, W. Xue, H. Wang, Journal of Chemical and Engineering Data, 61 (2016) 1192−1198. [2] F. Mota, A. Queimada,, S. Pinho, E. Macedo, Industrial and Engineering Chemistry Research, 47 (2008) 5182-5189. [3] Solubilities of Organic Compounds in Organic Solvents, J. Bradley, C. Neylon, R. Guha, A. Williams, B. Hooker, A. Lang, B. Friesen, Open Notebook Science, 2009.
- The impact of size and shape in the performance of hydrotropes: a case-study of alkanediolsPublication . Abranches, Dinis O.; Soares, Bruna de Paula; Ferreira, Ana M.; Shimizu, Seishi; Pinho, Simão; Coutinho, João A.P.Inspired by the recently proposed cooperative mechanism of hydrotropy, where water molecules mediate the aggregation of hydrotrope around the solute, this work studies the impact of apolar volume and polar group position on the performance of hydrotropes. To do so, the ability of two different families of alkanediols (1,2-alkanediols and 1,n-alkanediols) to increase the aqueous solubility of syringic acid is initially investigated. Interestingly, it is observed that in the dilute region (low hydrotrope concentration), the relative position of the hydroxyl groups of the alkanediols does not impact their performance. Instead, their ability to increase the solubility of syringic acid correlates remarkably well with the size of their alkyl chains. However, this is not the case for larger hydrotrope concentrations, where 1,2-alkanediols are found to perform, in general, better than 1,n-alkanediols. These seemingly contradictory findings are reconciled using theoretical and experimental techniques, namely the cooperative model of hydrotropy and chemical environment probes (Kamlet–Taft and pyrene polarity scales). It is found that the number of hydrotropes aggregated around a solute molecule does not increase linearly with the apolar volume of the former, reaching a maximum instead. This maximum is discussed in terms of competing solute–hydrotrope and hydrotrope–hydrotrope interactions. The results suggest that hydrotrope self-aggregation is more prevalent in 1,n-alkanediols, which negatively impacts their performance as hydrotropes. The results reported in this work support the cooperative model of hydrotropy and, from an application perspective, show that hydrotropes should be designed taking into consideration not only their apolar volume but also their ability to stabilize their selfaggregation in water, which negatively impacts their performance as solubility enhancers.
- Unveiling the mechanism of hydrotropy: Evidence for water-mediated aggregation of hydrotropes around the solutePublication . Abranches, Dinis O.; Benfica, Jordana; Soares, Bruna de Paula; Leal-Duaso, Alejandro; Sintra, Tânia E.; Pires, Elísabet; Pinho, Simão; Shimizu, Seishi; Coutinho, João A.P.A recent proposal attributes the origin of hydrotropy to the water-mediated aggregation of hydrotrope molecules around the solute. Experimental evidence for this phenomenon is reported for the first time in this work, using 1H-NMR. A new computational technique to quantify apolarity is introduced and is used to show that apolarity of both solute and hydrotrope is the driving force of hydrotropy. This journal is
- Vapor pressures and thermophysical properties of selected ethanolaminesPublication . Soares, Bruna de Paula; Štejfa, Vojtech; Ferreira, Olga; Pinho, Simão; Růžička, Květoslav; Fulem, MichalA thermodynamic study of three ethanolamines, 2-(diethylamino)ethanol, 2-(ethylamino)ethanol and 2- (isopropylamino)ethanol, reporting the measurements of vapor pressure, liquid phase heat capacities, and phase behavior is presented in this work. The vapor pressures were measured using a static method in the temperature interval 238e343 K. After a critical assessment of literature data, selected experimental data were correlated using the Cox equation. The liquid phase heat capacities were measured in the temperature range 265e355 K using Tian-Calvet calorimetry and the phase behavior was investigated using differential scanning calorimetry (DSC) starting from 183 K. For 2-(ethylamino)ethanol and 2-(isopropylamino)ethanol, two monotropically related crystalline forms were identified. To our knowledge, vapor pressure and heat capacity for 2-(isopropylamino)ethanol and phase behavior data for 2-(ethylamino)ethanol and 2-(isopropylamino)ethanol are reported for the first time in this work.