A systematic evaluation of Flow Field Flow Fractionation and single-particle ICP-MS to obtain the size distribution of organo-mineral iron oxyhydroxide colloids

Colloidal iron(III)oxyhydroxides (FeOx)are important reactive adsorbents in nature. This study was set up to determine the size of environmentally relevant FeOx colloids with new methods, i.e. Flow Field Flow Fractionation (FlFFF-UV-ICP-MS)and single-particle ICP-MS/MS (sp-ICP-MS)and to compare these with standard approaches, i.e. dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), microscopy (TEM), membrane filtration, centrifugation and dialysis. Seven synthetic nano- and submicron FeOx with different mineralogy and coating were prepared and two soil solutions were included. The FlFFF was optimized for Fe recovery, yielding 70–90%. The FlFFF determines particle size with high resolution in a 1 mM NH 4 HCO 3 (pH 8.3)background and can detect Fe-NOM complexes 4 HCO 3 )and it has acceptable element recoveries.