Browsing by Author "Batista, Marta"
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- Computational and experimental study of the behavior of cyano-based ionic liquids in aqueous solutionPublication . Batista, Marta; Kurnia, Kiki A.; Pinho, Simão; Gomes, J.R.B.; Coutinho, João A.P.The solvation of cyano- (CN-) based ionic liquids (ILs) and their capacity to establish hydrogen bonds (H-bonds) with water was studied by means of experimental and computational approaches. Experimentally, water activity data were measured for aqueous solutions of ILs based on 1-butyl-3-methylimidazolium ([BMIM](+)) cation combined with one of the following anions: thiocyanate ([SCN](-)), dicyanamide ([DCA](-)), or tricyanomethanide ([TCM](-)), and of 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][TCB]). From the latter data, water activity coefficients were estimated showing that [BMIM][SCN] and [BMIM][DCA], unlike [BMIM][TCM] and [EMIM][TCB], are able to establish favorable interactions with water. Computationally, the conductor like screening model for real solvents (COSMO-RS) was used to estimate the water activity coefficients which compare well with the experimental ones. From the COSMO-RS results, it is suggested that the polarity of each ion composing the ILs has a strong effect on the solvation phenomena. Furthermore, classical molecular dynamics (MD) simulations were performed for obtaining an atomic level picture of the local molecular neighborhood of the different species. From the experimental and computational data it is showed that increasing the number of CN groups in the ILs' anions does not enhance their ability to establish H-bonds with water but decreases their polarities, being [BMIM][DCA] and [BMIM][SCN] the ones presenting higher propensity to interact.
- Determinação de ácido ascórbico e ácido acetilsalicílico em formulações comerciais através de uma língua electrónicaPublication . Gomes, Cláudia; Gonçalves, Cristina; Borlido, Diana; Batista, Marta; Teixeira, Tatiana; Dias, L.G.; Pereira, Olívia R.A língua electrónica (LE) é um sistema de multi-sensores de sensibilidade cruzada, vocacionado para mimetizar o paladar humano e, por isso, uma ferramenta importante de auxílio à análise sensorial. Uma das possíveis aplicações na área farmacêutica é no teste de sabor dos medicamentos, por exemplo, na supressão do gosto amargo dos medicamentos por adição de substâncias doces, pois os aspectos sensoriais das formulações têm um efeito importante na adesão ao tratamento. No presente trabalho, pretendeu-se verificar as potencialidades da LE na análise quantitativa do ácido ascórbico (AAC) e do ácido acetilsalicílico (AAS) em diversas formulações farmacêuticas comerciais. As soluções padrão de calibração e soluções de fármacos foram analisadas por uma LE potenciométrica com 40 membranas lipo/poliméricas num suporte acrílico e usando um eléctrodo de referência de dupla junção Ag/AgCl. Os sinais obtidos foram relacionados com as concentrações das soluções através do método regressão linear múltipla (RLM), usando “stepwise” para selecionar as variáveis mais importantes. Os resultados preliminares da quantificação do AAC mostraram que o modelo RLM obtido tem uma relação linear aceitável entre concentrações obtidas pelo modelo de previsão e as esperadas (R2= 0.964). Na análise do AAS, o modelo de previsão mostrou um desempenho fraco já que a matriz dos medicamentos afectou significativamente os sinais dos sensores da LE. Globalmente, estes ensaios preliminares indicam que a LE pode ser usada para dosear AAC em formulações efervescentes mas, no caso do AAS será necessário alterar o procedimento ou usar outros sensores para que o efeito de matriz não seja significativo.
- Determination of ascorbic acid and acetylsalicylic acid in commercial preparations using an electronic tonguePublication . Pereira, Olívia R.; Gomes, Cláudia; Gonçalves, Cristina; Borlido, Diana; Batista, Marta; Teixeira, Tatiana; Dias, L.G.The electronic tongue is a multi-sensors system used to identify the basic standards of taste, such as sweet, salty, sour and bitter, at levels not detectable by humans. Although the main purpose of electronic tongue is the qualitative analysis, the quantitative analysis of substances in a liquid matrix is also possible, having been the subject of these preliminary studies the application of electronic tongue to pharmaceutical products. In this way, the aim of the current study was the quantitative analysis of ascorbic acid (AA) and acetylsalicylic acid (ASA) in several commercial preparations using an electronic tongue. Methods: For that, solutions of standard compounds or of commercial preparations contain ascorbic acid and acetylsalicylic acid were analizes by an electronic tongue. The obtained data were using to determine the concentrations of the solutions thought através do multiple linear regression method. Results: The preliminary tests showed that it is possible to quantify the ascorbic acid in effervescent formulations of vitamin C, using the predictor model obtained by multiple linear regression. In the case of acetylsalicylic acid it was verified that the matrix of the analgesics or antipyretics drugs significantly affect the signs of the electronic tongue. Conclusions: The electronic tongue can be used determined ascorbic acid in effervescent formulations while it is necessary developed more selective sensors to acetylsalicylic acid in order to improve the predictive power of electronic tongue quantification of this compound.
- Determination of ascorbic acid and acetylsalicylic acid in commercial preparations using an electronic tonguePublication . Pereira, Olívia R.; Gomes, Cláudia; Gonçalves, Cristina; Borlido, Diana; Batista, Marta; Teixeira, Tatiana; Dias, L.G.The electronic tongue is a multi-sensors system used to identify the basic standards of taste, such as sweet, salty, sour and bitter, at levels not detectable by humans. Although the main purpose of electronic tongue is the qualitative analysis, the quantitative analysis of substances in a liquid matrix is also possible, having been the subject of these preliminary studies the application of electronic tongue to pharmaceutical products. In this way, the aim of the current study was the quantitative analysis of ascorbic acid (AA) and acetylsalicylic acid (ASA) in several commercial preparations using an electronic tongue. For that, solutions of standard compounds or of commercial preparations contain ascorbic acid and acetylsalicylic acid were analizes by an electronic tongue. The obtained data were using to determine the concentrations of the solutions thought através do multiple linear regression method. The preliminary tests showed that it is possible to quantify the ascorbic acid in effervescent formulations of vitamin C, using the predictor model obtained by multiple linear regression. In the case of acetylsalicylic acid it was verified that the matrix of the analgesics or antipyretics drugs significantly affect the signs of the electronic tongue. The electronic tongue can be used determined ascorbic acid in effervescent formulations while it is necessary developed more selective sensors to acetylsalicylic acid in order to improve the predictive power of electronic tongue quantification of this compound.
- Why are some cyano-based ionic liquids better glucose solvents than water?Publication . Batista, Marta; Passos, Helena; Henriques, Bruno J.M.; Maginn, Edward J.; Pinho, Simão; Freire, Mara G.; Gomes, J.R.B.; Coutinho, João A.P.Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water – a well-known solvent with enhanced capacity to dissolve mono- and disaccharides. This raises questions on the ability of cyano groups to establish strong hydrogen bonds with carbohydrates and on the optimal number of cyano groups at the IL anion that maximizes the solubility of glucose. In addition to experimental solubility data, these questions are addressed in this study using a combination of density functional theory (DFT) and molecular dynamics (MD) simulations. Through the calculation of the number of hydrogen bonds, coordination numbers, energies of interaction and radial and spatial distribution functions, it was possible to explain the experimental results and to show that the ability to favorably interact with glucose is driven by the polarity of each IL anion, with the optimal anion being dicyanamide.