We discuss the features involved in determining the titanium dioxide nanoparticle (TiO2NP) sizes in cosmetic samples via single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in the millisecond-time resolution mode, and methods for considering the background signal. In the SP-ICP-MS determination of TiO2NPs in cosmetics, the background signal was recorded in each dwell time interval due to the signal of the Ti dissolved form in deionized water, and the background signal of the cosmetic matrix was compensated by dilution. A correction procedure for the frequency and intensity of the background signal is proposed, which differs from the known procedures due to its correction by the standard deviation above the background signal. Background signals were removed from the sample signal distribution using the deionized water signal distribution. Data processing was carried out using Microsoft Office Excel and SPCal software. The distributions of NP signals in cosmetic product samples were studied in the dwell time range of 4-20 ms. The limit of detection of the NP size (LODsize) with the proposed background signal correction procedure was 71 nm. For the studied samples, the LODsize did not depend on the threshold of the background signal and was determined by the sensitivity of the mass spectrometer.
Keywords: background signal correction; cosmetic products; single particle ICP-MS; titanium dioxide nanoparticles.