One of the most frequent questions we get at SOLVE is if we can characterize and quantitate nanoparticles in food and cosmetic products. ”Of course we can” said our scientists, ”let’s show them!”
Many consumer products contain nanoparticles – diameter 1-100 nanometers (one nanometer is 0.000001 millimeter). The most known product is probably sunsceen, where nanoparticles (typically titanium dioxide, TiO2, or zinc oxide, ZnO) are added to reflect UV radiation but without giving the ghostly look.
Several manufacturers argue that the added nanoparticles clump together in the sunscreen formula (forming aggregates) resulting in that no or few individual nanoparticles are present in the products.
Let's perform a study using the AF4 technique
We analyzed an ordinary kid’s sunscreen spray from a local pharmacy (with ”Titanium Dioxide (nano)” in the ingredients list) in order to show that we easily can detect and characterize potential nanoparticles using AF4.
Our scientists extracted the TiO2 particles in order not to influence or modify them and then injected them into the AF4 instrument. With AF4 connected online to detectors (such as MALS, dRI) it is possible to quantify and determine particle size (and size distribution) without the use of calibration standards.
The analyzed sunscreen contains nanoparticles, with diameters ranging from approx. 30 to 250 nm.
Verify that it really is TiO2
We collected fractions from the peak in AF4 (left figure, 2.5-7.5 min and 7.5-12-5 min) and determined the content of Ti by ICP-MS. We could verify that the particles are titanium dioxide and that the concentration was higher in the second part of the peak.