Asymmetric flow field flow fractionation of aqueous C 60 nanoparticles with size determination by dynamic light scattering and quantification by liquid chromatography atmospheric pressure photo-ionization mass spectrometry

Abstract

A size separation method was developed for aqueous C 60 fullerene aggregates (aqu/C 60) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may alter suspension characteristics. Aqu/C 60 aggregates generated by sonication in deionized water ranged in size from 80 to 260 nm in hydrodynamic diameter ( D h) as determined by DLS in flow through mode, which was corroborated by analysis of fractions by DLS in batch mode and by TEM. The mass of C 60 in each fraction was determined by LC–APPI–MS. Only 5.2 ± 6.7% of the total aqu/C 60 mass had D h less than 80 nm, while 58 ± 32% of the total aqu/C 60 mass had D h between 80 and 150 nm and 14 ± 9.2% of the total aqu/C 60 were between 150 and 260 nm in D h. With the optimal fractionation parameters, 77 ± 5.8% of the aqu/C 60 mass eluted from the AF4 channel, indicating deposition on the AF4 membrane had occurred during fractionation; use of alternative membranes did not reduce deposition. Channel flow splitting increased detector response although channel split ratios greater than 80% of the channel flow led to decreased detector response. This is the first report on the use of AF4 for fractionating a colloidal suspension of aqu/C 60.