Characterization and quantification of engineered nanoparticles in food by epithermal instrumental neutron activation analysis and electron microscopy

Abstract

Engineered nanoparticles (NPs) have increasingly been used in various areas including agriculture and food packaging, which may potentially cause contamination in food products. In this study, a combination of analytical techniques was used to detect, characterize, and quantify engineered NPs (cerium (IV) oxide (CeO2), silica (SiO2) NPs, and their mixture) in food matrices. A series of concentrations of CeO2, SiO2, and their mixtures from 0 to 0.75 wt% were mixed in soybean powders. The presence of engineered NPs was investigated using transmission electron microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. The average size of CeO2 and SiO2 was 28.5 and 30.5 nm in diameter, respectively. CeO2 NPs were irregular octahedral and cubic in shape, while SiO2 NPs were spherical. The concentration of NPs in soybean powders was analyzed by epithermal instrumental neutron activation analysis (EINAA). Calibration curves were plotted for quantification of NPs in soybean powders (R 2 = 0.996 and 0.994 for CeO2, SiO2 NPs in soybean powders, respectively; R 2 = 0.995 and 0.997 for CeO2 and SiO2 NP in a mixture in soybean powders, respectively). The study of the detection limit (DL) demonstrates that at 99 % confidence interval, EINAA can detect both NPs at 0.1 wt% in soybean powders. Satisfactory recoveries were obtained for samples with a concentration at and higher than the DL (86.2–104.7 % for CeO2 NPs and 85.7–95.2 % for SiO2 NPs; 87.5–101.3 and 85.6–93.5 % for CeO2 and SiO2 NPs in a mixture in soybean powders, respectively).