McGregor M A, Barnes G T
J Pharm Sci. 1978 Mar;67(3):364-7. doi: 10.1002/jps.2600670324.
Equilibrium surface pressure-area isotherms of dipalmitoyllecithin monolayers were measured on substrates containing various concentrations of the surfactant, cetrimonium (hexadecyltrimethylammonium) bromide. From these isotherms, the saturation adsorptions of surfactant for various surface lecithin concentrations were calculated. Plotting of these adsorptions against the inverse of the area per lecithin molecule, as required for the "accessible area" theory, revealed two linear segments, corresponding to penetrating at high and at low monolayer areas. At both high and low areas, the adsorption into the accessible areas of the surface was similar to adsorption at a monolayer-free surface. The effective cross-sectional area of the monolayer molecule in the low area region was equal to the collapse area; in the high area region, it was equal to an area corresponding to the co-area, as calculated from the Amagat equation. The change in cross-sectional area corresponded to the transition in the monolayer from a liquid condensed state to a liquid expanded state.
在含有不同浓度表面活性剂十六烷基三甲基溴化铵的底物上，测量了二棕榈酰卵磷脂单层的平衡表面压力-面积等温线。根据这些等温线，计算了不同表面卵磷脂浓度下表面活性剂的饱和吸附量。按照“可及面积”理论的要求，将这些吸附量与每个卵磷脂分子的面积的倒数作图，得到两个线性段，分别对应于高单层面积和低单层面积时的渗透情况。在高面积和低面积时，表面可及区域的吸附情况与无单层表面的吸附情况相似。低面积区域单层分子的有效横截面积等于塌陷面积；在高面积区域，它等于根据阿马伽特方程计算出的与共面积对应的面积。横截面积的变化对应于单层从液态凝聚态到液态膨胀态的转变。
