Mapping penetration of cosmetic compounds into hair fibers using time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS)

Abstract

In this communication, penetration of vegetable oils into hair fibers has been investigated by the TOF‐SIMS (Time‐Of‐Flight Secondary Ion Mass Spectrometry) method. In earlier work [1], the method was found suitable to study the penetration of coconut and mineral oils into human hair. Therefore, the study has been extended to a group of vegetable oils with different types of unsaturation in the fatty acid components. Different patterns of penetration have been observed for oils of different molecular structure. The general pattern which emerges from this study is that polyunsaturated oils do not penetrate at all, or do so only sparingly into the structure of hair. Most of these molecules seem to penetrate only into the cuticular region of the hair fiber. Oils with polyunsaturated fatty acids seem to have difficulty in penetrating hair. It is possible that these molecules do not fit into the fiber's cell membrane complexes, which are known to be the diffusion pathways in the keratin fiber. On the other hand, monounsaturated oils, such as olive oil, with more compact molecular structure seem to penetrate readily into the hair fiber.