An effective approach for size characterization and mass quantification of silica nanoparticles in coffee creamer by...

Silicon dioxide (SiO₂) has been used as a food additive (E551) for decades. However, some safety concerns have been raised recently due to the detection of silica nanoparticles (SiO₂ NPs) in a variety of foodstuffs and their unknown long-term health risk to humans. In order for risk assessment to be conducted, it is essential to establish a reliable, valid, and pragmatic method for analysis of SiO₂ NPs in foods for estimation of exposure. This paper presents an effective approach for both size characterization and mass quantification of SiO₂ NPs in commercial high-fat coffee creamer using asymmetric flow field-flow fractionation (AF4) coupled to inductively coupled plasma mass spectrometry (ICP-MS). SiO₂ NPs from coffee creamer were well extracted after cleanup with hexane in a two-phase (hexane vs. water) aqueous environment. Size determination of SiO₂ NPs was performed by on-line AF4-ICP-MS based on calibration with monodispersed standards. The dominant primary size of SiO₂ NPs in the studied sample was 36.5 nm. The mass percentages of SiO₂ NPs (vs. total SiO₂) were 18.6% for the dominant primary nano-silica particles by prechannel calibration and 35.7% for total SiO₂ NPs (≤ 100 nm) by postchannel calibration, with recoveries of 89-96% for the former and 75% for the latter. The established approach was demonstrated to be efficient and practical for routine analysis of polydispersed SiO₂ NPs with wide nano-size distribution in coffee creamer. This method may be extended to monitor the presence of SiO₂ NPs in other similar complex food matrices. Graphical abstract.