And finally Fig. 5d shows some cubical nanoparticles
(100–300 nm), which EDX analysis identifies as NaCl. Sodium
chloride nanoparticles could come from sodium in the food
container (they may contain sodium ionomers and the manufacturing
process is unknown, sometimes Ag nanoparticles are
produced in situ by reduction of AgNO3 by NaBH4 (Jang et al.,
2007)) or from sodium in the simulant solution. In any case we
do not know if those sodium chloride nanoparticles were present
as nanoparticles in the migration solution (the blank simulant
did not show them) or most likely were dissolved and crystallized
in nano-size in the process of drying the migration solution onto
the silicon chips.