Determination of anthocyanins and non-anthocyanin polyphenols by ultra performance liquid chromatography/electrospray ionization mass spectrometry (UPLC/ESI-MS) in jussara (Euterpe edulis) extracts.

This work aimed to propose two analytical methods for the quantitative and qualitative analysis of major anthocyanins and non-anthocyanin phenolic compounds in jussara (Euterpe edulis) extracts, using ultra performance liquid chromatography-mass spectrometry. These methods were evaluated for selectivity, precision, linearity, detection and quantification limits. The complete separation of 5 anthocyanins and 22 non-anthocyanins polyphenols was achieved in 4.5 and 7 min, respectively. Limits of detection ranged from 0.55 to 9.24 µg/L, with relative standard deviation for concentration up to 7.0%. In jussara extract, 13 of the 27 analytes were characterized. The dominant compound was cyanidin-3-O-rutinoside, representing about 73% of the total phenolic compounds content (approximately 23 mg/g of extract in dry weight). Other phenolic compounds found in the extract were: cyanidin-3-O-glucoside, pelargonidin-3-O-glucoside, quercetin, rutin, myricetin, kaempferol, kaempferol-3-O-rutinoside, luteolin, apigenin, catechin, ellagic acid and 4,5-dicaffeoylquinic acid.

The removal of reactive dyes from aqueous solutions using chemically modified mesoporous silica in the presence of anionic surfactant-the temperature dependence and a thermodynamic multivariate analysis.

The three-parameter Sips adsorption model was successfully employed to modeled equilibrium adsorption data of a yellow and a red dye onto a mesoporous aminopropyl-silica, in the presence of the surfactant sodium dodecylbenzenesulfonate (DBS) from 25 to 55 degrees C. The results were evaluated in relation to the previously reported surface tension measurements. The presence of curvatures of the van()t Hoff plots suggested the presence of non-zero heat capacities terms (Delta(ads)C(p)). For the yellow dye, it is observed that the values of Delta(ads)H are almost all positive and they decrease in endothermicity, in the absence and in the presence of DBS, from 25 to 55 degrees C. For the red dye, there is an increase in endothermicity in relation to the temperature increase. The negative Delta(ads)G values indicate spontaneous adsorption processes. Almost all adsorption entropy values (Delta(ads)S) were positive. This suggests that entropy is a driving force of adsorption. The adsorption thermodynamic parameters were also evaluated using a new 2(3) full factorial design analysis. The multivariate polynomial modelings indicated that the thermodynamic parameters are also affected by important interactive effects of the experimental factors and not by the temperature changes alone.

Aggregation and adsorption of reactive dyes in the presence of an anionic surfactant on mesoporous aminopropyl silica.

A surface tension technique was used to determine the critical aggregation concentration (cac) of a yellow and a red dye in relation to the presence of the anionic surfactant sodium dodecylbenzene sulfonate (DBS) and to temperature changes in buffered aqueous solutions. The cac values of the yellow dye increase from 25 to 45 degrees C (from 41.37 to 50.32 mg L-1) and decrease from 45 to 55 degrees C (from 50.32 to 38.72 mg L-1). The cac values for the red dye/DBS aggregates decrease (from 124.52 to 88.50 mg L-1) from 25 to 55 degrees C. Adsorption of the two dyes onto a mesoporous aminopropyl silica (Sil-NH2) was also studied. The adsorption of the yellow dye increases with an increase in temperature from 25 to 55 degrees C. In the presence of DBS the adsorption on Sil-NH2 for the yellow dye decreases, and for the red dye increases from 25 to 55 degrees C. Adsorptions occurred below and above the cac of the anionic dyes/DBS aggregates. Adsorption of the dyes onto Sil-NH2 fitted well to the Langmuir, Freundlich, and Redlich-Peterson adsorption models. However, in the presence of DBS, only the Freundlich model fit the experimental adsorption data at low dye concentrations (less than 400 mg L-1). In this case, the Redlich-Peterson model was only fitted to the red dye adsorption data. The magnitude of the Dubinin-Radushkevich energetic parameters (E, from 7.00 to 15.00 kJ mol-1) indicates that the adsorption of the dyes onto Sil-NH2, in the absence and in the presence of DBS, is controlled by water adsorbed/dye in solution ion-exchange interactions. It is observed that the values of DeltaadsH are positive for both dyes and the values are quite similar to each other. The exception is the adsorption of the yellow dye in the presence of DBS, which is slightly exothermic. The DeltaadsG values are all negative. However, the interactions of the dyes with Sil-NH2 silica are more spontaneous in the presence of the surfactant. The positive adsorption entropy values (DeltaadsS) for the interaction of the dyes suggest that entropy is a driving force of the dye adsorptions. However, the entropic contribution is higher for the adsorptions in the presence of DBS. It was suggested that the chemical structures of the dyes play an important role in the formation of the dye/DBS aggregates and in dye adsorption onto the aminopropyl silica.

The removal of anionic dyes from aqueous solutions in the presence of anionic surfactant using aminopropylsilica--a kinetic study.

In this study, the aminopropyl-silica (Sil-NH(2)) was used to adsorb a yellow- and a red-dye from aqueous solutions at pH 4.0. New data concerning the influence of the anionic surfactant SDS on the adsorption data was obtained. All interactions occurred below the cmc values of the Sil-NH(2)/anionic dyes aggregates. A rise of temperature accelerates the mass transfer of the red-dye into the Sil-NH(2) surface, while the yellow-dye adsorption decreased. The presence of SDS increased the adsorption quantities in relation to the temperature increasing. The exception is observed for the yellow-dye adsorption at 55 degrees C. So, it is suggested that the chemical structure of the dye, as well as the presence and position of its sulfonate groups are important factors that affect the anionic dye/SDS aggregations and the adsorption quantities. The solid-phase interactions of dyes data present good fittings to the Avrami kinetic model, where from two to four kinetic regions were found, taking into account the variations of the contact time and temperature. The presence of several values of Avrami constants, namely k(Av) and n, has been attributed to the occupation of both the surface and the internal adsorption sites of the aminopropyl-silica.