Extraction of Silicon-Containing Nanoparticles from an Agricultural Soil for Analysis by Single Particle Sector Field and Time-of-Flight Inductively Coupled Plasma Mass Spectrometry.

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., 14 N 14 N and 12 C 16 O) on 28 Si determinations. Consequently, a size detection limit of 29 ± 3 nm (diameter of spherical SiO 2 NP) was achieved in Milli-Q water. Si-NP were extracted from agricultural soil using several extractants, including Ca(NO 3 ) 2 , Mg(NO 3 ) 2 , BaCl 2 , NaNO 3 , Na 4 P 2 O 7 , fulvic acid (FA) and Na 2 H 2 EDTA. The best extraction efficiency was found for Na 4 P 2 O 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(NO 3 ) 2 , Mg(NO 3 ) 2 and BaCl 2 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 SiO 2 , ~30%).