Simultaneous Determination of Size and Quantification of Silica Nanoparticles by Asymmetric Flow Field-Flow Fractionation Coupled to ICPMS Using Silica Nanoparticles Standards

This work proposes the use of multimodal mixtures of monodispersed silica nanoparticles (SiO2-NPs) standards for the simultaneous determination of size and concentration of SiO2-NPs in aqueous suspensions by asymmetric flow field-flow fractionation (AF4) coupled to inductively coupled plasma mass spectrometry (ICPMS). For such a purpose, suspensions of SiO2-NPs standards of 20, 40, 60, 80, 100 and 150 nm were characterised by transmission electronic microscopy (TEM), centrifugal liquid sedimentation (CLS), dynamic light scattering (DLS) and by measuring the Z-potential of the particles as well as the exact concentration of NPs by off-line ICPMS. An on-line AF4-ICPMS method which allowed the separation of all the different sized SiO2-NPs contained in the mixture of standards was developed and the analytical figures of merit were systematically evaluated. The method showed excellent linearity in the studied concentration range (0.1-25 mg L-1), limits of detection between 0.16 and 0.3 mg L-1 for smaller and greater particles, respectively, besides a satisfactory accuracy. AF4 calibration with particles with identical nature to those to be analysed, also permitted accurate size determination in a pragmatic way. Similarly, by using pre-channel calibration with NPs for mass determination it was possible to overcome common quantification problems associated to losses of material during the separation and size-dependent effects. The proposed methodology was successfully applied to the characterisation in terms of size and concentration of aqueous test samples containing SiO2-NPs with monomodal size distributions.JRC.I.1-Chemical Assessment and Testin