General overview »
Magnetic Nanoparticles »
Standardization »
Characterization and
analysis methods »
DC magnetization and AC
susceptometer analysis »
Medium and high frequency
AC susceptometry »
Mössbauer spectroscopy »
Electron microscopy »
XRD and SAXS »
SANS »
Electron microscopy »
Ferromagnetic resonance »
Dynamic light scattering and
electrophoretic light scattering »
Field-flow fractionation »
Magnetic modelling »
Magnetorelaxometry »
Magnetic particle spectroscopy »
Magnetic particle rotation »
Magnetic separation »
NMR R1 and R2 relaxivities »
Magnetic nanoparticle bio-detection »
Magnetic hyperthermia measurements »
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Field-flow fractionation
Field-flow fractionation (FFF) – with subcategories asymmetrical flow FFF (AF4) and sedimentation FFF (SdFFF) – is a family of techniques that can be used to size fractionate magnetic nanoparticles (MNP) across a wide size range. FFF can be utilized for the determination of the MNP hydrodynamic radii from elution times as well as the radius of gyration with in-line multiangle light scattering detection. Furthermore, the light scattering detection together with other detectors (such as SAXS) can give an insight into structural properties such as apparent densities and shape/conformational properties over the entire size distribution. The difference between hydrodynamic size and core size allows detection of the particles’ shell size. The amount of shell material and its composition can be determined by thermogravimetry which is coupled with FTIR and mass spectrometry (TG-FTIR and TG-MS, respectively). States of oxidation, bond distances and coordination of iron atoms will be revealed with X-ray absorption fine structure spectroscopy (XAFS) in form of XANES and EXAFS.
The FFF technique fractionates nanoparticles in a low shear, low pressure single liquid phase environment which preserves fragile aggregate species and maximizes sample recovery. Fraction collection is easy for additional off-line characterization or to provide monodisperse nanoparticle samples. The FFF method allows for the fractionation of nanoparticles in a variety of environments such as high and low pH, different salts and concentrations, and solutions which mimic conditions in the body or the environment. FFF can assess changes in MNP physicochemical properties or behaviour with respect to health and safety considerations such as biological toxicity or environmental fate or manufacturing parameters such as processing, storage and packaging.
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