Unveiling the potential of confocal raman spectroscopy in the analysis of oil permeation in human hair fibers

Purpose: Hair is subject to damage, and the challenge is to find oils that can permeate the hair fiber to its inner layers, providing protection. This study aimed to analyze the permeation of copaiba, andiroba, and coconut oils into human hair fibers using confocal Raman spectroscopy (CRS). Materials and methods: Five untreated hair fibers (control) and five treated fibers were used, with 10 μl of each oil applied to the treated fibers. Raman spectra were collected before and after 30 minutes of treatment, from the surface to a depth of 40 μm. Data preprocessing involved removing fluorescence, smoothing, and vector normalization. After data processing, biochemical characterization, identification of marker peaks, and calculation of the area under the curve were performed to detect the permeation profile of each oil. Results: Quantification of the permeated oil concentration showed a similarity between the permeation of copaiba oil (30.14 a.u.) and coconut oil (27.85 a.u.), both reaching the deepest layer of the fiber (medulla). Andiroba oil also permeated to the deepest layer but showed a lower concentration (14.09 a.u.). These differences in concentration (a.u.) can be attributed to the biochemical composition of the oils, especially concerning the degree of saturation. Conclusions: Therefore, the CRS technique demonstrated that all three oils permeated to the innermost layer of the hair fiber, providing greater insight into their permeation capacity. This knowledge allows for their varied use in the industry, including for the recovery of damaged hair, making it healthier.