Size and concentration determination of (functionalised) fullerenes in surface and sewage water matrices using field flow fractionation coupled to an online accurate mass spectrometer: Method development and validation

In order to assess the environmental risks of a compound it is imperative to have suitable and reliable techniques for its determination in environmental matrices. In this paper, we focused on a method development for the recently introduced online coupling of a field flow fractionation (FFF) system to an Orbitrap-HRMS, that allows the simultaneous size and concentration determination of different aqueous fullerene aggregates and their concentrations in different size fractions. A 0.05% NH₄OH solution in water was identified as the best carrier liquid for the analysis of the three different aqueous fullerene suspensions (C₆₀ 60], 6,6]-phenyl-C₆₁ butyric acid methyl ester (60]PCBM) and 6,6]-(bis)phenyl-C₆₁ butyric acid methyl ester (60]bisPCBM)). The multi-angle light scattering (MALS) data received after employing the ammonia solution was consistent with both the theory and calibration using well defined Au and latex particles. The LODs obtained using Orbitrap HRMS detection were 0.1 μg L⁻¹ for an injection volume of 100 μL which are significantly better than the LODs obtained by using UV (20 μg L⁻¹) and MALS detectors (5 μg L⁻¹). However, these LODs can be further improved as in theory there is no limit to the amount of sample that can be injected into the FFF. Environmental samples (river and sewage water) were spiked with fullerenes and the fractograms obtained for these samples revealed that the matrix does affect the size of fullerene aggregates. Information on the size distribution can be useful for the risk assessment of these particles.