Na2co3

Citric acid (C₆H₈O₇, Scharlau, Barcelona, Spain) was used as the neutralizing agent for alkali solutions and sodium carbonate (Na₂CO₃, Scharlau, Barcelona, Spain) was used as an acid neutralizer. Calcium chloride dihydrate (CaCl₂ 2H₂O, Merck, Darmstadt, Germany) served as an ionic gelling agent when forming microspheres of sodium carbonate containing sodium alginate at 1 wt%, ((C₆H₇O₆Na)_n, M = 10,000–600,000 g/mol, PanReac AppliChem ITW Reagents, Barcelona, Spain). Microcapsules of citric acid encapsulated in hydrogenated palm oil (84.4% (w/w), 509.6 ± 167.0 µm) (MIRCAP CT 85-H) were kindly supplied by VEDEQSA (Venta de Especialidades Químicas, S.A., Barcelona, Spain). Alkali solutions were prepared using sodium hydroxide (NaOH, pellets, Merck, Darmstadt, Germany). Acid solutions were prepared using hydrochloric acid (HCl 37% (v/v), Merck, Darmstadt, Germany). Polypropylene Absorbent Mat Pad MAT 412 was used as substrate (thickness of 4.37 ± 0.17 mm).

Native potato starch (29 wt% amylose content, 15.5 wt% moisture) as a film-forming material was supplied by Nowamyl S.A., hoary willowherb Epilobium parviflorum (E) was purchased from Dary Natury (Grodzisk, Poland) and glycerol (anhydrous) used as a plasticizer was obtained from Chempur (Piekary Śląskie, Poland). DPPH–(2,2-diphenyl-1-picrylhydrazyl radical) (Tokyo Chemical Industry Co., Tokyo, Japan) and methanol (pure, Chempur) were used for the evaluation of antioxidative properties. Folin-Ciocalteau reagent (Eurochem BGD, Tarnów, Poland), gallic acid (p.a. 97.5–102.5%, Sigma-Aldrich, Milan, Italy) and Na₂CO₃ (anhydrous, reagent grade, Scharlau, Barcelona, Spain) were applied for the measurement of total phenolic compounds content in the extract and the films.

Polysulfone membrane sheet, PS (PS-20), (Sepro, California, CA, USA). Merck supplied 1,3-phenylenediamine (C₆H₈N₂, 99.5%) and 1,3,5-benzenetricarbonyl trichloride (C₉H₃Cl₃O₃, 98%) (Kenilworth, New Jersey, NJ, USA). Short multiwalled carbon nanotubes (MWCNTs) with a purity of 95% and average diameter of 3–10 nm was provided by Grafen Chemical Industries (Ankara, Turkey). MWCNTs COOH and MWCNTs-NH₂) are thin multiwalled carbon nanotubes that have been functionalized. MWCNT samples with a purity of 95% were obtained from Nanocyl (Sambreville, Belgium). Hexane (C₆H₁₄, 99%) was purchased from Oxford Laboratory (Mumbai, India). Sodium chloride (NaCl, 99%) was purchased from Sigma-Aldrich Chemicals (Hamburg, Germany), while anhydrous magnesium sulfate (MgSO₄, 98%) and extra pure anhydrous sodium carbonate (Na₂CO₃, 99.5%) were obtained from Scharlau (Barcelona, Spain). Absolute ethanol (96%) was purchased from Ajax Finechem Pty, Ltd. (South Wales, Australia). Milli-Q^® water (18.2) was used to make both solutions and dilutions in this study.