Supramolecular solvent-based extraction of benzimidazolic fungicides from natural waters prior to their liquid chromatographic/fluorimetric determination

A supramolecular solvent made up of vesicles of decanoic acid in the nano- and microscale regimes dispersed in a continuous aqueous phase is proposed for the extraction/preconcentration of benzimidazolic fungicides (BFs) from river and underground water samples prior to their determination by liquid chromatography (LC)/fluorimetry. The solvent is produced from the coacervation of decanoic acid aqueous vesicles by the action of tetrabutylammonium (Bu₄N⁺). Carbendazim (CB), thiabendazole (TB) and fuberidazole (FB) are extracted on the basis of hydrophobic and π-cation interactions and the formation of hydrogen bonds. The extraction provides high preconcentration factors (160 for CB and 190 for TB and FB), requires a short time (the procedure takes less than 20 min and several samples can be simultaneously processed) and a low sample volume (20 mL), and avoids the use of toxic organic solvents. Because of the absence of matrix interferences and the low viscosity of the extracts, these can be directly injected into the chromatographic system without the need of cleaning-up or diluting them. Recoveries are not influenced by the presence of salt concentrations up to 1 M. The proposed method provides detection limits for the determination of CB, TB and FB in natural waters of 32, 4 and 0.1 ng L⁻¹, respectively, and a precision, expressed as relative standard deviation (n = 11) of 5.5% for CB (100 ng L⁻¹), 4.0% for TB (80 ng L⁻¹) and 2.5% for FB (30 ng L⁻¹). Recoveries obtained by applying this approach to the analysis of river and underground water samples fortified at the ng L⁻¹ level are in the intervals 75–83, 95–102 and 97–101% for CB, TB and FB, respectively.     

Interaction between components of plant-based biopolymer systems

Proteins and polysaccharides are key elements in formulated foods, cosmetics, and pharmaceuticals. Their interaction behavior mainly determines the organoleptic, optical, textural, and rheological properties of foods. Traditionally, animal-based biopolymers have been widely used because of their excellent techno-functionality; however, plant-based alternatives gained enormous interest among scientists and manufacturers because of sustainable, religious, ethical, and nutritional reasons. The directed complexation of mixed biopolymers entirely originated from plants might be used to stabilize food colloids, modulate interfacial and bulk properties, control the release of bioactives, and mask bitter components. As such, this review highlights the general separation mechanism of mixed biopolymers systems entirely composed of plant-based biopolymers to be used as functional food ingredients. Particularly, ‘traditional’ and ‘novel’ proteins and polysaccharides obtained from different plant sources (e.g. soy, wheat, pea, potato, apple, citrus) are introduced to be assembled to modulate interfacial and bulk properties of food colloids.     

Determination of bisphenols A and F and their diglycidyl ethers in wastewater and river water by coacervative extraction and liquid chromatography-fluorimetry

A simple, rapid and sensitive analytical method was developed for the simultaneous determination of bisphenol A (BPA), bisphenol F (BPF) and their corresponding diglycidyl ethers (BADGE and BFDGE) in wastewater and river water, in order to have a useful tool for evaluating their fate and distribution in aquatic environments. It was based on their extraction with coacervates made up of decanoic acid reverse micelles and subsequent determination by liquid chromatography-fluorimetry. The procedure involved the extraction of 10.8 mL of water sample for 5 min, its centrifugation for 10 min to accelerate phase separation and then the chromatographic analysis of the target compounds. Clean-up or solvent evaporation steps were not necessary to get the required sensitivity and selectivity. Extraction efficiencies and concentration factors mainly depended on the amount of decanoic acid and tetrahydrofuran making up the coacervate. A general equation for the prediction of the volume of the coacervate as a function of its components has been proposed and fitted by nonlinear regression. This equation permits to know a priori the maximum concentration factors that can be achieved under given experimental conditions. Extractions were independent of salt addition (up to 1 M), the temperature (up to 60 °C) and the pH (below 4) rendering the method robust. Recoveries in samples ranged between about 80 and 92% and the actual concentrations factors were between 87 and 102, which resulted in practical detection limits around 30-35 ng L⁻¹. The method was successfully applied to the determination of the target pollutants in raw and treated sewage from four mechanical-biological treatment plants and three rivers. Bisphenols and their diglycidyl ethers were present in wastewater influents at concentrations in the range 0.96 to 1.6 μg L⁻¹. The biological treatment at the wastewater treatment plants (WWTP_s) studied reduced the concentration of BPA and BPF in a percentage above 75%, while diglycidyl ethers were not detected in most of the effluents investigated. Only BPA was detected in surface waters.     

Determination of Etofenprox in environmental samples by HPLC after anionic surfactant micelle-mediated extraction (coacervation extraction)

A method is described for determination of residues of the insecticide Etofenprox in environmental samples. Anionic surfactant micelle-mediated extraction (coacervation extraction) was evaluated for isolation of Etofenprox before HPLC. The optimum conditions used for extraction included: 0.09 g sodium dodecanesulfonate (SDoS), 3.1 mL (3.3, for concentrations below 0.04 mg L⁻¹) 12 mol L⁻¹ HCl, 5 min vortex stirring, 5 min centrifugation at 4000 rpm, 2 h equilibration time. The limits of quantification (LOQ) and detection (LOD) were 0.01 and 0.004 mg L⁻¹, respectively, and recoveries obtained from five real samples ranged from 94.33±2.48 to 100.13±2.71%. The precision of the method was good; relative standard deviations (RSD) were less than 7%.      

Preparation and Evaluation of Theophylline Sustained Release Microcapsules Using Coacervation

Preparation of sustained release dosage forms is one of the main objectives in drug formulation. Theophylline that has a narrow therapeutic index, making it a good choice to prepare a sustained release dosage form. Theophylline sustained release microcapsules were prepared by applying the coacervation method. The effect of the type and ratio of polymers, as well as the type of washing solvents, was studied on particle size, drug loading efficiency, and in vitro drug release profile. Results showed that Eudragit RS and RL could be more suitable polymers for preparation of sustained release microcapsules of theophylline when used in ratio of 1:1 and when the washing solvent was hexane.     

Preparation and Characterization of Oil Containing Microcapsules Obtained by an Interaction Induced Coacervation

A novel method for microencapsulation of oil by coacervation is presented. The method employs segregative phase separation between sodium carboxymethyl cellulose (NaCMC) and a complex of hydroxypropylmethyl cellulose (HPMC) and sodium dodecylsulfate (SDS), which results in coacervate formation. Microstructural properties of the coacervate can be varied by tuning NaCMC-HPMC/SDS interaction, which is achieved by changing SDS concentration. Microcapsules preparation route is presented. Encapsulation efficiency and dispersion properties of microcapsules with coacervate shell of different properties and different oil content were tested. Microcapsules with smallest droplet size, the narrowest droplet size distribution, and with lowest extractability of encapsulated oil were obtained when NaCMC-HPMC/SDS interaction results in formation of the most compact coacervate shell, no matter of the encapsulated oil.     

The Role of Chemically Innocent Polyanions in Active,Chemically Fueled Complex Coacervate Droplets

Complex coacervation describes the liquid-liquid phase separation of oppositely charged polymers. Active coacervates are droplets in which one of the electrolyte's affinity is regulated by chemical reactions. These droplets are particularly interesting because they are tightly regulated by reaction kinetics. For example, they serve as a model for membraneless organelles that are also often regulated by biochemical transformations such as post-translational modifications. They are also a great protocell model or could be used to synthesize life–they spontaneously emerge in response to reagents, compete, and decay when all nutrients have been consumed. However, the role of the unreactive building blocks, e.g., the polymeric compounds, is poorly understood. Here, we show the important role of the chemically innocent, unreactive polyanion of our chemically fueled coacervation droplets. We show that the polyanion drastically influences the resulting droplets′ life cycle without influencing the chemical reaction cycle–either they are very dynamic or have a delayed dissolution. Additionally, we derive a mechanistic understanding of our observations and show how additives and rational polymer design help to create the desired coacervate emulsion life cycles.     

单凝聚与复凝聚法制备昆虫激素十二醇微胶囊及其释放行为

通过向明胶溶液中加入硫酸钠溶液的单凝聚方法以及将明胶溶液加入到阿拉伯胶溶液的复凝聚方法,制备了聚合物包覆昆虫激素十二醇的水分散体系微胶囊.通过对凝聚过程中ζ电位与透光率跟踪测试确定了单凝聚中加入硫酸钠的最佳用量以及复凝聚中明胶与阿拉伯胶的相对量.在壁材浓度大于或等于3%条件下制备的复凝聚胶囊的尺寸大于单凝聚微胶囊,但后者的大小分布更均一.除非在2%壁材浓度下,其他条件下复凝聚制备的胶囊的十二醇包覆率明显高于单凝聚胶囊.对胶囊中十二醇在恒湿恒温条件下的释放研究表明,单凝聚胶囊中十二醇很快释放完毕,变化壁材浓度不明显改变其释放行为.相比之下复凝聚胶囊中十二醇的释放对壁材浓度有明显的依赖性.2%壁材浓度制备的胶囊其释放行为类似于单凝聚胶囊;但3%到5%壁材浓度制备的胶囊中十二醇的释放明显分为3个区间,即较快的初始释放、较长时间的恒速释放以及最后阶段释放速率的再次提高直至释放完毕.复凝聚胶囊中十二醇的释放表现出了明显的可控性.文中亦对该体系中昆虫激素十二醇的释放机理作了初步讨论.     

PHASE STABILITY OF LYOTROPIC LIQUID CRYSTAL SYSTEMS

Theoretical considerations of supramolecuiar organization in lyotropic liquid crystal systems are presented. The model describes the lamellar, inverted hexagonal and micellar phases and the phase transitions between them. Experimental and calculated by the model data are in good agreement.