Particle size and concentration are determined separately, meaning that any measurements do not influence other parameters. Concentration analysis is also based on single-particle measurements, ensuring highly accurate calculations for each size band.

TRPS measures every particle that passes through the pore to ensure that a true size distribution is reported. Furthermore, DLS only measures the hydrodynamic diameter of particles and as a result may not be an accurate representation of particle diameter. Although MADLS aims to improve on the DLS measurement any inaccuracies in initial particle size determination will be propagated through the calculation of total particle concentration, resulting in inaccurate determination of this parameter as well. It is a fast, convenient and relatively simple technique, enabling absolute estimates of particle size for a wide range of colloidal suspensions including suspended metal nanoparticles. However, the concentration of large particles can be significantly overestimated due to the sextic dependence of light-scattering intensity, skewing the particle size distribution. Dynamic light scattering (DLS) (also known as photon correlation spectroscopy) is one of the most widely used techniques for the study of colloidal systems. Light-scattering techniques like DLS offer simple approaches to obtaining bulk estimates of the size and concentration of particles in solution. Electrophoretic mobility and surface charge are calculated from the speed at which the particle traverses the pore. Particle concentration is calculated from the particle flow rate measured at several different applied pressures. Particle size is determined for individual particles. Particles crossing the pore cause transient changes in the flow of an ionic current, the magnitude of which are proportional to particle size. TRPS monitors current flow through a tunable nanopore (Figure 2). The intensity-weighted particle size distribution is then transformed into particle concentration distribution. For both DLS methods, total particle concentration is calculated from the photon count rates. The Nano DS is the first nanoparticle size analyzer to combine Dynamic Light Scattering (DLS) and Static Light Scattering (SLS) in the same particle size. Multi-angle DLS (MADLS) is a variation of DLS which assesses particle size distribution by analysing multiple scattering autocorrelation functions, usually recorded at three angles. By applying a scattering autocorrelation function, the average hydrodynamic diameter of particles in the sample can be calculated. DLS involves applying a laser beam to the sample and monitoring fluctuations in the scattering intensity which results from the Brownian motion of the particles (Figure 1).

Dynamic light scattering nanoparticle