Physical properties of lipids used in pharmacy. I. Screening raw materials via photomicrography.

A simple photomicrographic technique has been devised to screen lipids for integrity of their crystal structure. In this technique, thin films of the materials are prepared on microscope slides and photomicrographs are taken of their surface and internal structures. The samples are then stored at normal or exaggerated temperatures for any desired period of time. At various intervals, the exact areas appearing in the original photomicrographs are rephotographed and compared with the originals. These permanent records permit detection of subtle changes which occur during aging. The technique has been used with a number of individual materials and simple mixtures. Representative photomicrographs are presented showing the structural integrity of carnauba wax, cetyl alcohol, hydrogenated soya oil, lauryl monoethanolamide, stearyl alcohol, and white wax.