Comparative study of titanium dioxide to improve the quality of finished cosmetic products.

Abstract

Titanium dioxide (TiO2 ) pigments (pure) or with a hydrophobic coating of triethoxycaprylylsilane (TECSi) used in cosmetics. Using different methods, we studied properties of commercially available pure and coated pigment. We determined the elemental composition of pigments that differ in their behaviour in a cosmetic formulation. The significant differences in the coating composition were revealed. UV-Vis absorption spectroscopy allowed us to investigate the pigment purity and determined the polymorph form in pigments. FTIR was employed to identify functional groups present in the samples with the modified surface. XRD, DLS, TEM and DCS were applied to characterize particle size and morphology. The experiment of ED-XRF method was used to determine the elemental composition of pigments that differ in their behaviour in a cosmetic formulation. UV-Vis spectroscopy was used to detect organic pollutants in particular batches, which were not detected in the cases of the tested samples. Solid UV-Vis spectroscopy and XRD revealed which crystalline form of TiO2 is present in pigments. TEM and DLS methods were used to characterize particle size and morphology as well as DCS method, which provide more accurate information about form (separated or clustered particles) of pigments' particles in suspensions. Based on FTIR spectra, the presence of a coating in the raw material was identified, and the tell-tale signal of the silane group. On the contrary, spectroscopy of washed-out product can identify the well or poorly modified pigment. Applying ED-XRF, it turned out that the content of silicon (and consequently of the TECSi) was lower than that declared by the manufacturer. Our data indicate how we can recognize poorly coated pigments in raw material. The results show that ED-XRF method is nondestructive, effective and fast, hence, can be successfully introduced into preproduction pigment control in cosmetic industry.