Inverse supercritical fluid extraction as a sample preparation method for the analysis of the nanoparticle content in sunscreen agents

Abstract

We demonstrate the use of inverse supercritical carbon dioxide (scCO2) extraction as a novel methodof sample preparation for the analysis of complex nanoparticle-containing samples, in our case a modelsunscreen agent with titanium dioxide nanoparticles. The sample was prepared for analysis in a simplifiedprocess using a lab scale supercritical fluid extraction system. The residual material was easily dispersedin an aqueous solution and analyzed by Asymmetrical Flow Field-Flow Fractionation (AF4) hyphenatedwith UV- and Multi-Angle Light Scattering detection. The obtained results allowed an unambiguousdetermination of the presence of nanoparticles within the sample, with almost no background fromthe matrix itself, and showed that the size distribution of the nanoparticles is essentially maintained.These results are especially relevant in view of recently introduced regulatory requirements concerningthe labeling of nanoparticle-containing products. The novel sample preparation method is potentiallyapplicable to commercial sunscreens or other emulsion-based cosmetic products and has importantecological advantages over currently used sample preparation techniques involving organic solvents.