Fast and non-destructive neutron activation analysis for simultaneous determination of TiO2 and SiO2 in sunscreens with attention to regulatory and research issues

A new instrumental neutron activation analysis (INAA) for the simultaneous determination of titanium (TiO2) and silica (SiO2) dioxide as UV-filters in sunscreens is described. Samples are encapsulated, neutron irradiated (30 s) and after a suitable decay (3 min), the induced Ti-51 (T-1/2 = 5.76 min) and Al-29 (T-1/2 = 6.56 min) radionuclides are measured for the emitted gamma-ray fingerprint. Three applications were carried out: (i) screening study (analysis of commercial sunscreens in combination with single particle inductively coupled plasma mass spectrometry (sp-ICP-MS); (ii) research study (development of inno-vative UV-filters such as titanium dioxide or bismuth titanate loaded inorganic mesoporous silica nanoparticles, MSN); (iii) validation study (intercalibration of a spectrochemical method - inductively coupled plasma optical emission spectrometry, ICP-OES). Collectively, the nuclear method appears a powerful tool adequate for quantifying TiO2 and SiO2 in the above studies. The limited accessibility at the nuclear reactor for neutron activation is probably one of the reasons why the excellent characteristics of the nuclear technique are not always fully known and exploited in the industrial and research chemical world. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This article describes a new instrumental neutron activation analysis (INAA) for the simultaneous determination of titanium dioxide (TiO2) and silica dioxide (SiO2) as UV-filters in sunscreens. The method utilizes the measurement of induced radionuclides' emitted gamma-ray fingerprint and has been successfully applied in screening, research, and validation studies.