Department of Microbioanalytics, Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland.
Colloids Surf B Biointerfaces. 2013 Aug 1;108:95-102. doi: 10.1016/j.colsurfb.2013.02.008. Epub 2013 Feb 21.
Surface activity of Sigma's Quillaja bark saponin (QBS) was studied by means of dynamic interfacial tension and surface dilational rheology at three fluid/fluid interfaces with the polarity of the non-aqueous phase increasing in the order: air/water, tetradecane/water and olive oil/water. The equilibrium interfacial tension isotherms were fitted to the generalized Frumkin model with surface compressibility for the air/water and tetradecane/water interfaces, whereas the isotherm for the third interface displays a more complex shape. Upon fast compression of a drop of concentrated "Sigma" QBS solution immersed in olive oil, a clearly visible and durable skin was formed. On the other hand, no skin formation was noticed at the air/water interface, and only a little at the tetradecane/water interface. Addition of a fatty acid, however, improved slightly the skin-formation ability of the QBS at the latter interface. The surface behavior of the QBS from Sigma was compared with that from Desert King, Int. ("Supersap"), employed in a recent study by Stanimirova et al. [22]. The two products exhibit different areas per molecule in the saturated adsorbed layer (0.37nm(2) vs. 1.19nm(2) for "Sigma" and "Supersap", respectively). Also their surface rheology is different: although both QBSs form predominantly elastic layers, for "Sigma" the surface storage modulus, εr=103mNm(-1), while for "Supersap" εr=73mNm(-1) at 10(-3)moll(-1) (i.e., around their cmc). The two saponin products exhibit also different ionic character, as proven by the acid-base titration of their aqueous solutions: QBS from Sigma is an ionic surfactant, while the "Supersap" from Desert King is a non-ionic one.
采用动态界面张力和表面扩张流变学方法，在三个具有不同极性的流体/流体界面上研究了 Sigma 奎那亚树皮皂苷（QBS）的表面活性，非水相的极性顺序增加：空气/水、十四烷/水和橄榄油/水。空气/水和十四烷/水界面的平衡界面张力等温线符合广义 Frumkin 模型，表面可压缩性；而第三个界面的等温线则呈现出更复杂的形状。当快速压缩浸入橄榄油中的浓缩“Sigma”QBS 溶液的液滴时，会形成一个清晰可见且持久的皮膜。另一方面，在空气/水界面上没有注意到皮膜形成，而在十四烷/水界面上只有一点。然而，添加脂肪酸略微改善了 QBS 在后者界面上的皮膜形成能力。Sigma 的 QBS 的表面行为与 Stanimirova 等人在最近的研究中使用的 Desert King，Int.（“Supersap”）的 QBS 进行了比较[22]。这两种产品在饱和吸附层中每个分子的面积不同（Sigma 为 0.37nm²，Supersap 为 1.19nm²）。此外，它们的表面流变学也不同：尽管两种 QBS 都主要形成弹性层，但对于 Sigma，表面储存模量 εr=103mNm(-1)，而对于 Supersap，在 10(-3)moll(-1)（即其 cmc 左右）时 εr=73mNm(-1)。这两种皂苷产品还表现出不同的离子特性，这可以通过它们的水溶液的酸碱滴定来证明：Sigma 的 QBS 是一种离子表面活性剂，而 Desert King 的 Supersap 是一种非离子表面活性剂。
