Extraction of Silicon-Containing Nanoparticles from an Agricultural Soil for Analysis by Single Particle Sector Field...

The increased use of silica and silicon-containing nanoparticles (Si-NP) in agricultural applications has stimulated interest in determining their potential migration in the environment and their uptake by living organisms. Understanding the fate and behavior of Si-NPs will require their accurate analysis and characterization in very complex environmental matrices. In this study, we investigated Si-NP analysis in soil using single-particle ICP-MS. A magnetic sector instrument was operated at medium resolution to overcome the impact of polyatomic interferences (e.g., ¹⁴N¹⁴N and ¹²C¹⁶O) on ²⁸Si determinations. Consequently, a size detection limit of 29 ± 3 nm (diameter of spherical SiO₂ NP) was achieved in Milli-Q water. Si-NP were extracted from agricultural soil using several extractants, including Ca(NO₃)₂, Mg(NO₃)₂, BaCl₂, NaNO₃, Na₄P₂O₇, fulvic acid (FA) and Na₂H₂EDTA. The best extraction efficiency was found for Na₄P₂O_7, for which the size distribution of Si-NP in the leachates was well preserved for at least one month. On the other hand, Ca(NO₃)₂, Mg(NO₃)₂ and BaCl₂ were relatively less effective and generally led to particle agglomeration. A time-of-flight ICP-MS was also used to examine the nature of the extracted Si-NP on a single-particle basis. Aluminosilicates accounted for the greatest number of extracted NP (~46%), followed by NP where Si was the only detected metal (presumably SiO₂, ~30%).