Black Film Method surfactants

Black Film Method for Assessment of Therapeutic Surfactants... 

Bubble of size of the order of tens of micrometers floating on the surfactant surface only little deviates from the spherical shape. This fact has been used in the method of diminishing bubble [128,129] which allows to measure the contact angle of the black film, the linear tension of the contact line film/meniscus and the coefficient of the gas permeability through the film. Fig. 2.24 presents the scheme of this device. 

In order to determine the infants lung maturity and the necessity of surfactant therapy it is of great importance to substantiate the functionality of the alveolar surfactant, derived via invasive techniques [13], Several techniques and models have been largely used to investigate inteifacial physicochemical properties in vitro and to assess clinical efficiency of ES in vivo the Langmuir monolayer technique in combination with Wilhelmy plate method for surface tension measurements and black foam film method for determination of the ability of ES for stable film formation [14]. The pendant drop method combined with the Axisym-metric Drop Shape Analysis (ADSA) has been also used for similar purposes [4,15-18]. 

In the method developed by Exerowa, Cohen and Nikolova [144] the insoluble (or slightly soluble) monolayers are obtained by adsorption from the gas phase. A special device (Fig. 2.28) was constructed for the purpose a ring a in the measuring cell of Scheludko and Exerowa for formation of microscopic foam films at constant capillary pressure (see Section 2.1.2.). The insoluble (or slightly soluble) substance from reversoir b is placed in this ring. Conditions for the adsorption of the surfactant on either surface of the bi-concave drop are created in the closed space of the measuring cell. The surfactant used was n-decanol which at temperatures lower than 10°C forms a condensed monolayer. Thus, it is possible to obtain common thin as well as black foam films. The results from these studies can be seen in Section 3.4.3.3. 

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