The application of nanoparticles (NPs) in science and technology is a fast growing field. Therefore, reliable and
straightforward analytical methods are required for their fast determination in different types of samples. This
work investigates a method that enables the determination of ZnO NPs, discriminating them from ionic zinc in
cosmetic samples. The method is based on direct solid sampling high-resolution continuum source electrothermal
atomic absorption spectrometry (SS-HR-CS-GFAAS), and has been applied to determination of ZnO NPs, Zn2+
and total Zn in eye shadow samples. In this work the deconvolution of the atomization peak and the calibration
by standard additions have been done in order to discriminate and quantify ionic zinc and ZnO NPs. A Zn
wavelength with low sensitivity was selected. The proper optimization of the graphite furnace temperature
program, minimizing the mineralization of the sample matrix, enables different atomization profiles between the
different chemical species of the analyte. Two multiple response surface designs have been used in order to
optimize the adequate furnace program to achieve our aims. All the optimization experiments were performed
using a sample of eye shadow. Further, a method for the determination of total Zn by direct solid sampling with
calibration by aqueous standards, was also optimized. The optimized method was successfully applied to the
determination of ionic Zn and ZnO NPs in different eye shadow samples, and has been validated by recovery
assays, obtaining recovery percentages between 80 and 125%. Total Zn concentration in the solid samples was
validated by the determination of total Zn by direct solid sampling and by the analysis of the same eye shadow
samples digested in microwave oven.
