Improved sample preparation and quality control for the characterisation of titanium dioxide nanoparticles in sunscreens using flow field flow fractionation on-line with inductively coupled plasma mass spectrometry

Abstract

Titanium dioxide in nanoparticulate form is used in large scale in a variety of consumer products including sunscreens. There is an increasing need for methodology for the reliable characterisation of the particle size and size dependent elemental composition in these complex matrices. Such measurement capability is essential for underpinning safety assessments, for quality control of existing products and for correlation of nanoparticle characteristics with biological effects observed in toxicity tests. This work describes the first systematic comparison and optimisation of extraction methods for titanium dioxide nanoparticles in sunscreen samples. Sunscreens were selected because of their wide use, high fat content and matrix of high complexity. Defatting of the sample with hexane followed by bath sonication with an aqueous extractant was found to provide stable suspensions of secondary titanium dioxide particles for their size characterisation by flow field flow fractionation on-line with element selective detection by inductively coupled plasma mass spectrometry. Further addition of a small amount of hexane to the aqueous extractant resulted in particle disaggregation and thus allowed for characterisation of the primary particle size. A novel approach based on sample spiking with aluminium-labelled titanium dioxide reference particles of known size was used to study the effect of extraction and separation conditions on particle size distribution in the presence of the real sample matrix. The developed methodology was applied to analysis of commercial sunscreens with various sun protection factors. Titanium extraction efficiency, particle size distribution and titanium dioxide recovery from the FFF channel were determined for each product.

Total synthesis of isotopically enriched Si-29 silica NPs as potential spikes for isotope dilution quantification of natural silica NPs

“…biological systems) are urgently needed. In the last few years the popularity of on-line field-flow fractionation (FFF) coupled with inductively coupled plasma mass spectrometry (ICP-MS) in the characterisation of various nanomaterials has increased significantly [1][2][3][4][5][6][7][8]. FFF-ICP-MS allows NP sizing, size-based elemental speciation and quantification of the nano-sized fraction in the presence of complex matrix components.…”

Field flow fractionation online with ICP-MS as novel approach for the quantification of fine particulate carbon in stream water samples and soil extracts

“…In addition the larger particle size in soil extracts compared to water samples may contribute to increased signal noise, which is typically observed for metallic nanoparticles with increasing size. 3 Compared to the water sample in Fig. 4 the particle size distribution of the predominant fraction for carbon is much broader which is partly due to slight differences in the FFF separation conditions, but mainly due to higher concentration of larger carbon containing particles in the soil extracts.…”

Current uses of nanomaterials in biocidal products and treated articles in the EU

“…Similar output is also possible with other tools such as asymmetric flow field flow fractionation (AF4) combined with ICP-MS or UV-Vis. 43,44 Other products that have been addressed in the literature and experimentally investigated include various dietary supplements that contain Ag nanoparticles, 45,46 disinfectant sprays with Ag or ZnO NPs 47,48 and different food products such as e.g. chicken meat with Ag.…”