ALTERNATING-CURRENT TAST-POLAROGRAPHIC DETERMINATION OF SURFACE-ACTIVITY OF LUNG SURFACTANT

It is demonstrated that lung surfactant, like DL-α-lecithin, acts as a typical surface active substance in phase-selected alternating current tast-polarography. It lowers both the electrical double-layer capacity and the surface tension on the mercury electrode/saline interface and gives rise to characteristic adsorption-desorption capacity peaks. Capacity decrease, peak height, and diminution of the supporting electrolyte hump are controlled by the quantity, i.e. surface activity, of lung surfactant. A linear relationship between the logarithm of capacity values and surface activity measured with the de Noüy ring method is derived. Based on these facts it is possible to express surface activity of lung surfactant in capacity terms and to use the phase-selected alternating current tast-polarography in surface activity studies of lung surfactant. © 1979 Elsevier Sequoia S.A.