The NanoFlowSizer further explained
Dynamic light scattering (DLS) is an accepted technology for measuring particle size and size distribution of nanoparticles in liquids. It is based on measurement of fluctuations in light scattering caused by Brownian motion of suspended particles. For Brownian diffusion, the frequency of scattered intensity fluctuations depends on the particle size; smaller particles diffuse more rapidly and thus produce higher frequencies. Therefore, the temporal fluctuations in light scattering hold information on the particle size.
Standard DLS measurements need to be performed under static conditions ensuring that particle movement is solely caused by Brownian motion and not influenced by other factors like liquid flow. Additionally, standard DLS cannot be applied to the turbid suspension which are often encountered in industrial or process environments. This limits the use of standard DLS for inprocess applications.
These limitations can be overcome by the new concept of Spatially Resolved Dynamic Light Scattering (SRDLS) which allows particle size characterization in process flows and for highly turbid suspensions. The NanoFlowSizer technology is based on low coherence interferometry providing light scattering information as function of optical pathlength in process flows.
The depth resolved light scattering holds information on particle movement caused by both Brownian motion as well as flow rate. The contribution to scattered light fluctuations due to Brownian motion is used for calculation of the particle size characteristics.
Other key advantages of the NanoFlowSizer are the capability to distinguish single from multiple scattered light, and the high measurement speed. The XsperGo software automatically identifies and selects single scattered light allowing measurement of highly turbid suspensions in flow. Additionally, the high datainformation content and high speed processing, provide characteristics such as mean particle size and distribution typically within 10 seconds. These clear advantages make the NanoFlowSizer the ideal solution for inline measurements, providing continuous real-time process feedback on nanoparticle size characteristics, a powerful Process Analytical Tool.
SR-DLS without flow: (left) temporal depth resolved scattering data as basis for (right) auto correlation functions showing single and multiple scattering regimes. The single scattering regime is automatically identified and used for particle size characterization.
NanoFlowSizer measurements are performed through glass preventing any direct contact or interference with the sample, which makes the technology ideally suited for continuously monitoring (sterile) processes.