"FFF-Raman Coupling for Particle Analysis"
With the rising awareness of micro- and nanoplastic pollution in the environment, also the interest in different approaches for the detection of these particles is increasing. While there are several techniques available for the microplastic size range that can provide concentration, size and material characterization, for the nanoplastic size range only recently a technique was developed that could provide this information within a single measurement: An online-coupled field flow fractionation (FFF)-UV-multiangle light scattering (MALS)-Raman approach. It could be shown that this technique allows for particle detection in a size range that is not accessible to common optical microscopy methods. The FFF system is used to separate particles in the size range of 100 nm to 5 μm and the MALS detector can provide the corresponding size information. In this work asymmetric flow FFF (AF4) and centrifugal FFF (CF3) are used to achieve particle separation for different mixtures of synthetic particles. A custom designed flow cell enables the chemical characterization via Raman microspectroscopy in an online coupled mode to the FFF systems. Using the optical forces (optical tweezers) of the Raman laser, particles are trapped in the focus of the laser beam long enough for spectral acquisition. In the field of nanoplastics this setup has been validated for polystyrene (PS), polyethylene (PE) and polymethylmethacrylate (PMMA) so far. Inorganic particles (SiO2, TiO2, FexOy) can in some cases not only be detected, but also their polymorphs might be distinguished with this technique. Especially for environmental samples there is a great need for the differentiation between nanoplastics and other inorganic particles. Thus, the latest results on the simultaneous separation and characterization of both nanoplastics and inorganic particles will also be presented.