ToF‐SIMS characterization of the lipid layer on the hair surface. I: the damage caused by chemical treatments and UV radiation

Abstract In this study, we investigated how the lipids bound to the outermost surface of human hair are affected by chemical treatments such as hair bleach and ultraviolet (UV) radiation using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Many lipid components are bound covalently via a thioester or ester linkage on the outermost surface of hair. We studied how these components are changed by chemical treatment. It was found that the fatty acids covalently bound via a thioester linkage are removed more easily than those with an ester linkage. Eighty percent of the 18‐MEA (18‐methyleicosanoic acid), which is a major component of lipids, was removed in a single bleach treatment, and most had vanished entirely after three treatments. We also investigated the influence of UV radiation and found that the amount of 18‐MEA decreased with the radiation time. More than 90% of the 18‐MEA was removed by UV radiation with corresponding exposure of three summer months. Copyright © 2010 John Wiley & Sons, Ltd.