Resolving Concentrated Particle Size Mixtures Using Dynamic Light Scattering

Abstract

Dynamic light scattering (DLS) is a technique used for measuring the size of molecules and particles undergoing Brownian motion by observing time‐dependent fluctuations in the intensity of scattered light. The measurement of samples using conventional DLS instrumentation is limited to low concentrations due to the onset of a phenomenon called multiple scattering. The problems of multiple scattering have been addressed in a light scattering instrument incorporating non‐ invasive backscatter optics (NIBS). This novel optic arrangement maximizes the detection of scattered light while maintaining signal quality and allows for measurements of turbid samples. This paper discusses the ability of backscatter detection to accurately determine particle sizes at 1 %w/v sample concentrations and demonstrates the correct resolution of different size populations using a series of latex standard mixtures with known volume ratios. The concentration of 1 %w/v is much higher than can be measured on conventional dynamic light scattering instruments.

DLS and zeta potential – What they are and what they are not?

“…An inherent weakness of DLS is its low resolution [85]. For example, DLS is unable to distinguish between particles of 90 and 110 nm and a broad peak with high PDI will appear.…”

Separation and characterization of gold nanoparticle mixtures by flow-field-flow fractionation

“…The standard approach to measure the size of nanoparticles in solution is to use dynamic light scattering (DLS) measurements. The technique can be applied to both diluted and concentrated solutions [9] but has a limited power at resolving mixtures mainly due to the fact that particles contribution to the scattering intensity depends by the sixth power of their radius [10,11]. The accurate and sensitive determination of size distribution of nanoparticles in complex mixtures will likely become even more important in the near future if the proposed definition of nanomaterial as containing more than 1% of the total number of particles in the 1-100 nm size range will be adopted by the European Union.…”

A method for identifying small molecule aggregators using photonic crystal biosensor microplates

“…Particle diameter measurements of all 22 samples were obtained (including the negative controls), but with large standard deviations and particle size readings of ~100 nm particle diameter for the negative controls (DMSO, biotin, and buffer) severely limited the B A utility of the data obtained. DLS measurements of scattering intensity can be used as a means for estimating particle diameter based upon Mie-theory calculations that assume uniform spherical particles [5,7]. However, if the particles do not fit this model, the results are inconsistent, as shown by our results.…”

“…Of the 22 compounds tested, the PC biosensor assay measured no aggregation for several compounds (1,2,3,4,5,6,7,14,16,17,18) in addition to three negative controls (DMSO, biotin, and buffer). Several compounds resulted in measured aggregation with the PC assay (8,9,10,11,12,13,15,19,20), in addition to the positive control (CR) ( Figure 4).…”

“…The positive control, Congo Red (CR), has consistently been shown to be prone to aggregation. DLS was used to measure the ability of each molecule to aggregate as a result of the scattering intensity of solutions of each molecule [6,7]. Nonspecific inhibition of enzyme-based reactions is a hallmark of promiscuous inhibitors, and so an α-chymotryspin-based enzyme inhibition assay was also used across the small molecule library [3].…”