Conductivity of two micellar systems was measured in order to determine critical micelle concentration (CMC) of cetyltrimethylammonium bromide (CTAB). Those systems were: CTin water and CTin binary mixture acetonitrile (ACN)-water. Conductivity (?)-concentration (c) data were treated by four different methods: conventional method, differential methods (first and second derivative) and method of integration (methods A-D, respectively). As CTin water micellar system shows a sharp transition between premicellar and postmicellar part of the ?/c curve, any of the applied methods gives reliable CMC values and there is no statistically significant difference between them. However, for CTin ACN-water mixture micellar system the integration method for CMC determination is recommended due to a weak curvature of ?/c plot.

Winemaking generates large quantities of grape waste consisting of seeds, skin and stalks. Given that grape seeds are a rich source of different bioactive compounds, the main goal of this research was to optimize grape seed phenol extraction using a Box–Behnken design. The following conditions were derived from the optimization process: sample:solvent ratio of 1:10 w/v, extraction time of 30 min and extraction temperature of 50 °C. In addition, a sustainable (green) approach for obtaining extracts was developed by comparing choline chloride:citric acid-ChCit (natural deep eutectic solvent (NADES)) and ethanol extraction methods with respect to phenol profiles and antioxidant activity. This study was conducted on seeds from eight different red grape varieties. Phenolic acids, flavan-3-ols and procyanidins were characterized using HPLC–MS/MS, and the concentration of procyanidin B1 was above 1 mg/g of dry weight in all analyzed samples. The contents of all phenol classes and antioxidant activities were found to not differ significantly between the solvents, but NADES was found to offer valuable advantages. Importantly, ChCit showed a strong affinity toward procyanidins and a strong correlation between antioxidant activity and quantified phenolic compounds.