Surface tension characterizes the behavior of substances at interfaces. There is a growing interest in the surface properties of protein suspension surfaces in pharmaceutical applications, so we measured the surface tension of two pharmaceutically relevant protein suspensions with different surfactant concentrations. In the theoretical part, we define and describe surface tension and how it changes in the presence of surfactants. Surface tension is measured with the pendant drop method, which is a simple optical method for measuring surface tension and can be very accurate if certain factors are taken into account. In the following, we describe the physical basis of the method, present the Bond and Worthington numbers, the principle of computer image analysis, and the required measuring equipment. Measurements of surface tension of pure water with addition of surfactant are followed by measurements of two protein suspensions. Various parameters of measured liquids are presented in graphs and accompanied with commentary. The results for pure water are comparable with literature data. Due to the similarities between water and the protein suspensions, we conclude on the reliability of the results for both protein suspensions. In the final part of the thesis, we summarize the results, further analyze them, and provide comments. We also mention the usefulness of measuring time dependence of surface tension, for which the pendant drop method is very convenient.
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