The research team at the Food and Drug Administration, Ministry of Health and Welfare, inTaiwan found that these proposed measurement methods were shown to be ‘highly effective’and also provided consistent information related to nanoparticles and their interactions in the formulations.
In their study, published in the International Journal of Cosmetic Science, the team used Transmission electron microscopy (TEM) coupled with a window-type microchip K-kit/copper grid and X-ray diffraction (XRD) to characterise titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles in sunscreen sprays.
They were looking to characterise the size, shape, and composition of the particles as well as their aggregation/agglomeration characteristics.
Treatment methods
TEM pre-treatment was performed using two approaches: using a conventional copper grid (requiring dilution) and using a K-kit (not requiring dilution).
The scientists say that the use of a K-kit in conjunction with XRD makes it possible to obtain direct measurements from samples that have not undergone pre-treatment, which could otherwise alter the nature of the samples, such as the degree of agglomeration.
XRD was used to obtain information related to particle size and crystal structure. A strong correlation was observed between XRD and TEM measurements, and the team say the methods are ‘highly effective’.
Labelling
Many products on the market contain titanium dioxide) and zinc oxide nanoparticles, but the researchers say that many of these are not labelled as containing them.
A survey conducted by the International Cooperation on Cosmetic Regulations (ICCR) reported the widespread use of TiO2 and ZnO nanoparticles for the absorption of UVA/UVB radiation in skin care products.
As per European regulation, commercial products containing nanomaterials must be registered at least 6 months prior to release on the market.
Notification of intent to manufacture nanomaterials must include the name of the chemical (IUPAC) as well as the sizes, physicochemical information and toxicity.