Particle size characterization of titanium dioxide in sunscreen products using sedimentation field-flow fractionation–inductively coupled plasma–mass spectrometry

Abstract

Sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry (SdFFF-ICP-MS) was successfully applied to investigate particle size distribution of titanium dioxide (TiO(2)) in sunscreen samples after hexane extraction to remove organic components from the samples. Three brands of sunscreen products of various sun protection factor (SPF) value were used as samples. Different particle size distribution profiles were observed for sunscreen samples of various brands and SPF values; however, the particle size distributions of titanium dioxide in most sunscreen samples investigated in this work were larger than 100 nm. The titanium dioxide concentrations were higher for the products of higher SPF values. By comparing the results obtained from online SdFFF-ICP-MS and those from the off-line ICP-MS determination of titanium after acid digestion, ICP-MS was found to effectively atomize and ionize the titanium dioxide particle without the need for acid digestion of the samples. Therefore, the online coupling between SdFFF and ICP-MS could be effectively used to provide quantitative information of titanium dioxide concentrations across particle size distribution profiles.

Analysis of engineered nanomaterials in complex matrices (environment and biota): General considerations and conceptual case studies

“…Titanium dioxide is quite resistant to classical digestion techniques such as concentrated nitric acid, which offers some freedom in the use of digestive methods to destroy the matrix materials. Several digestion methods have been studied for the separation of TiO 2 out of sunscreen and preparation of a target particle dispersion for subsequent FFF analysis [80]; others performed a diluted direct injection or hexane liquid/liquid extraction of hydrophobic compounds before injection [81]. Neither study performed a full quantitative analysis of the ENP fraction.…”

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…Clean-up procedures based on the defatting by hexane extraction have been used for the analysis of sunscreens containing TiO 2 [52][53][54] and foods containing SiO 2 [55].…”

“…Depending on the type of matrix, different digestion strategies (enzymatic, TMAH-based or acidic), clean-up with organic solvents or lixiviation with water have been described, followed by a centrifugation or a filtration step. For particle disaggregation, bath or tip sonication is usually required, although the addition of hexane was found to be useful in the case of TiO 2 NPs in sunscreens [52][53][54]154]. In any case, these pre-treatments can affect the subsequent FFF separation.…”

Surface Modification of Titanium Dioxide for Nobel White Pigment With Condensed Phosphoric Acid Treatment

“…1 TiO2 is well known to exhibit photocatalytic activity; therefore, photocatalytic decomposition of sebum on the skin exposed to ultraviolet radiation (sunlight) might occur. To suppress this effect, various technical processes have been investigated and applied.…”