Using light scattering to evaluate the separation of polydisperse nanoparticles

Abstract

The analysis of natural and otherwise complex samples is challenging and yields uncertainty about the accuracy and precision of measurements. Here we present a practical tool to assess relative accuracy among separation protocols for techniques using light scattering detection. Due to the highly non-linear relationship between particle size and the intensity of scattered light, a few large particles may obfuscate greater numbers of small particles. Therefore, insufficiently separated mixtures may result in an overestimate of the average measured particle size. Complete separation of complex samples is needed to mitigate this challenge. A separation protocol can be considered improved if the average measured size is smaller than a previous separation protocol. Further, the protocol resulting in the smallest average measured particle size yields the best separation among those explored. If the differential in average measured size between protocols is less than the measurement uncertainty, then the selected protocols are of equivalent precision. As a demonstration, this assessment metric is applied to optimization of cross flow (Vx) protocols in asymmetric flow field flow fractionation (AF4) separation interfaced with online quasi-elastic light scattering (QELS) detection using mixtures of polystyrene beads spanning a large size range. Using this assessment metric, the Vx parameter was modulated to improve separation until the average measured size of the mixture was in statistical agreement with the calculated average size of particles in the mixture. While we demonstrate this metric by improving AF4 Vx protocols, it can be applied to any given separation parameters for separation techniques that employ dynamic light scattering detectors.

Asymmetric flow field flow fractionation with light scattering detection – an orthogonal sensitivity analysis

“…Further, when a broad size distribution of particles is inadequately separated and sized by optical techniques, the highly non-linear response of light scattering causes an over representation of the larger particles in the measured sample (light scattering intensity scales with particle radius to the 6 th power [29][30][31][32]). Identifying a separation protocol that is of sufficient selectivity allows for both the large and small particles to be detected separately, resulting in an overall lower average measurement and yielding the best possible separation considering the sample polydispersity and instruments' operational limits [33].…”

Synthesis of Polyurethane/TiO2 Hybrid with High Encapsulation Efficiency Using One‐Step Miniemulsion Polymerization for Methylene Blue Degradation and its Antibacterial Applications

“…However, the PSD of both PU hybrids (Figure 2) did not exhibit a bimodal peak. This could be explained by the detection restriction of the low scattering light intensity of small particles with the constraints of the DLS instrument [40] . Generally in an emulsion system, smaller droplets have a high surface area and low thermodynamic stability compared to the higher thermodynamic stability of large droplets.…”

“…This could be explained by the detection restriction of the low scattering light intensity of small particles with the constraints of the DLS instrument. [40] Generally in an emulsion system, smaller droplets have a high surface area and low thermodynamic stability compared to the higher thermodynamic stability of large droplets. With time, smaller droplets are deposited and diffused to form larger droplets.…”