The methods classified as macroscopic fitting include light scattering, x-ray scattering, neutron scattering, and acoustic spectroscopy. All of these methods rely on measuring a certain property of a sample that contains particles and then calculating the particle size distribution from the measured raw data using an appropriate theory. For instance, in the case of static light scattering instruments, the raw data is the intensity of scattered light versus angle. Calculation of the particle size distribution requires a theory which relates this information to particle size. For calculating the grain size in liquid for your case, preferable is DLS which can determine the hydrodynamic radius of particles.
Malvern Instruments supplies two unique technologies for measuring particle concentration namely; Nanoparticle Tracking Analysis (NTA) and Resonant Mass Measurement (RMM).These two technologies provide concentration measurement across a wide dynamic range of concentrations and sizes, with a range of complimentary measurands also available such as particle size, single particle zeta potential, particle mass measurement and particle fluorescence.
Cryo-SEM involves the examination of biological material at below ambient temperature (typically between -100 oC and -175 oC), allowing the life-like appearance of the sample to be preserved and recorded in the fully hydrated and chemically unmodified state.