Titanium Dioxide in Commercial Sunscreens: the Morphological Characterization and the Quantification

Due to nanotechnology's advancement, the application of nanomaterials in commercial products, including in sunscreens, has been increased rapidly. Physical sunscreens employ Titanium dioxide (TiO₂) or Zinc oxide (ZnO) nanoparticles as UV filter materials. Indonesian National Agency of Drug and Food Control regulates that TiO₂ rutile polymorph, size distribution ≥30 nm, and maximum concentration of 25% are criteria for physical sunscreen marketed in Indonesia. However, most of these products do not indicate the detailed inorganic material information in the product ingredients, resulting in the increasing concern of nanoparticle’s risk to human health and the environment. Therefore, the size, type of crystal structure, and amount of TiO2 or ZnO must be closely monitored. In this work, we investigated the morphological structure of TiO_2, including quantified its concentration in some commercial sunscreens marketed in Indonesia. TiO₂ was characterized using different characterization techniques. XRD analysis revealed that some studied sunscreens employed anatase TiO_2, which is not suggested to be added in a sunscreen product. HRTEM analysis proved that the sizes of materials in sample S1-S3 are below 50 nm, and silica-coated TiO₂ was observed in S4. Quantification of Titanium using GF-AAS yielded Ti's concentration in the range of 1400-7800 µg g^-1 (0.14-0.79%). To the best of our knowledge, this is the first study to report the physical properties and the concentration of TiO₂ nanoparticles (NPs) in commercial sunscreen marketed in Indonesia.