Characterization of Structure-Surface Correlations in Ointments Using Surface Tensiometry within the Concept of an Integrated Analytical Approach

In recent years, integrated data analysis has proven to be a valuable method for investigating complex systems, whether artificial or natural. The integrated analytical approach allows the simultaneous integration of data acquired from different analytical techniques employed for the same sample at the same time, leading to an expansion of the amount of information available. Surface tensiometry is a technique that was recently introduced in the Integrated Analytical Approach for investigating pharmaceutical dosage forms for topical application. Therefore, studies of rheological characterization, release, and skin permeation can be integrated with surface tensiometry measurements to develop chemical and rheological-surface correlation models, providing a new method for the quality control and process control of semisolid preparations. In this context, the aim of this research is to validate the utility of surface tensiometry measurements in the Integrated Analytical Approach and utilize these data to gain insights into the structure-surface correlation. The preparations chosen for this study were a PEG-gel, a lipogel, and an O/W cream containing carnitine as a model drug. The formulations were characterized using rheological measurements and evaluated for their carnitine release performance. Furthermore, surface tensiometry measurements were performed to rapidly and noninvasively assess the influence of carnitine on the surface properties of the semisolid preparations investigated. Our work demonstrated a close correlation between surface energy and structural data, showing the importance of surface tensiometry contribution in the noninvasive and rapid evaluation of the presence of carnitine in semisolid formulations.