An effective approach for size characterization and mass quantification of silica nanoparticles in coffee creamer by AF4-ICP-MS

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.