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Inspecting the Nanoparticle Content in Sunscreens

A fast and environmentally friendly procedure for the efficient analysis of titanium dioxide nanoparticles in commercial sunscreens

As the number of commercial nanoparticle-containing products is booming, it is becoming increasingly important to develop reliable analytical procedures for the efficient characterization of nanoparticle content. There is also a clear need to shift towards greener analytical techniques to reduce solvent use. Tight control over the amount of nanoparticles in cosmetic products is critical both for consumer health and for the environment, and new regulations have been introduced by the European Union to that end. A challenge lies in the difficulty of extracting the nanoparticles from a complex sample, such as titanium dioxide nanoparticles in sunscreens. In the case of sunscreens, the nanoparticles have to be extracted from a mixture containing often more than 20 ingredients, and the viscosity of the sample makes injection into an analytical instrument difficult. To circumvent the need for ecologically harmful organic solvents, which are commonly used in sample preparation protocols, a new approach is desirable that should both mitigate the environmental impact and simplify the overall procedure.

In their work, Dr. David Müller and collaborators have developed a new method for the analysis of nanoparticles in commercial sunscreen that comprises two analytical steps. They first use inverse supercritical fluid extraction (inverse SFE), an extraction procedure that is typically applied for the extraction of caffeine from coffee beans. Here the inverse SFE method is used to simplify the matrix of the sample by dissolving unwanted components. Supercritical carbon dioxide is used as the supercritical fluid to efficiently remove fatty additives from the sample. The second treatment step is asymmetrical flow field-flow fractionation (AF4), a method commonly used for the separation of macromolecules and particles in a suspension based on their size. A novelty here is the miniaturization of the AF4 platform to enable faster processing as well as decreased solvent consumption.

The developed procedure was successfully applied for the analysis of commercial sunscreens containing variable amounts of titanium dioxide nanoparticles, enabling fast and reproducible characterization of the nanoparticle content for both quantification and size determination. Considering the wide applicability of the method, this work is a valuable contribution to efforts towards developing environmentally sound analytical techniques.

Written by Julie Probst

Read the full paper here.

It is crucial to control the release of nanoparticles in the environment and ensure manufacturer compliance.

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