Determination of Titanium Dioxide in Commercial Sunscreens by Inductively Coupled Plasma–Optical Emission Spectrometry

Abstract

A variety of sunscreen products have been developed to afford the consumer protection against some of the deleterious effects, for example erythema, caused by solar ultraviolet radiation. The requirement that suncare products offer broad-spectrumprotection has resulted in the use of inorganic oxides, such as micronized titanium dioxide (TiO₂), in their formulation. However, there are now concerns about the photocatalytic effects of the TiO₂ in these products and its potential phototoxicity to the skin through the generation of reactive oxygen species such as hydroxyl and superoxide anion radicals. It is important, therefore, that the amounts of TiO₂ in suncare products be closely monitored and maintained within stipulated ranges. A simple, fast and reliable analytical method for the determination of TiO₂ in commercial sunscreen products by inductively coupled plasma–optical emission spectrometry (ICP-OES) was developed and validated. The limits of detection and quantitation were found to be 0.018 and 0.062 μg mL^–1, respectively. The average percentage recovery of TiO₂ was 102.32 ± 2.87 % with a RSD of 2.81 %. The method was applied to determine the concentration of TiO₂ in 22 commercial suncare samples of which 14 contained TiO₂. The amounts of TiO₂ measured in these sunscreens ranged from 0.05 to 3.21 %. To our knowledge this is the first study that reports the amounts of TiO₂ in sunscreen products available on the South African market.

Keywords: Titanium dioxide, sunscreens, physical blocker, inductively coupled plasma-optical emission spectrometry