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

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journal contribution
posted on 17.12.2015, 07:29 by Francisco Barahona, Otmar Geiss, Patricia Urbán, Isaac Ojea-Jimenez, Douglas Gilliland, Josefa Barrero-Moreno
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 characterized 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 offline ICPMS. An online 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 analyzed, also permitted accurate size determination in a pragmatic way. Similarly, by using prechannel calibration with NPs for mass determination it was possible to overcome common quantification problems associated with losses of material during the separation and size-dependent effects. The proposed methodology was successfully applied to the characterization in terms of size and concentration of aqueous test samples containing SiO2–NPs with monomodal size distributions.