Microfiltration of Submicron-Sized and Nano-Sized Suspensions for Particle Size Determination by Dynamic Light Scattering

Abstract

Dynamic light scattering (DLS) is commonly used for the determination of average particle diameters and suspension stability and popular in academics and industry. However, DLS is not considered suitable for polydisperse samples. The presence of little quantities of micrometre particles in nano and submicrometre suspensions especially affect the reliability of DLS results. Microfiltration might be a suitable method for the removal of unwanted large particles. This study investigates the effect of microfiltration on the diameter distributions as measured by DLS. Polystyrene standards (40–900 nm diameter), and monomodal silica suspensions were filtered with polytetrafluoroethylene (PTFE) membranes (0.1–1.0 µm pore size) to investigate retention properties and grade efficiency. Non-ideal materials were used to prove the results. Experiments showed that a mono-exponential decay can be achieved by filtration. A size safety factor of at least three between labeled pore size and average diameter was found to keep separation as low as possible. Filtration in order to enhance DLS for particulate submicrometre materials was considered suitable for narrowly distributed coated titania and kaolin powder. In a regulatory context, this might have an impact on considering a substance false positive or false negative according to the European Commission (EC) recommendation of a definition of the term nanomaterial.

Obtaining and Characterizing the Osmium Nanoparticles/n–Decanol Bulk Membrane Used for the p–Nitrophenol Reduction and Separation System

“…The study conditions for each method of analysis were as follows: Dynamic light scattering (DLS) analysis: granulometry equipment: Coulter N4 Plus (He–Ne laser, 632.8 nm); analysis range: 3–3000 nm; detection angle: 10.7°; RT analysis temperature: 23 °C ±1; stabilization time at RT: 5 min; analysis time: auto; data collection time: 5 min × 10 (repetitions); ultrasound time (US): 5 min (20 kHz, RT); rest time after US: ~24 h; dispersion medium (solvent): i –propanol; sample dilution: ~1:500. Size distribution processor (SDP) analysis: ultrasound time (US): 5 min (20 kHz, RT); rest time after US: ~24 h [ 26 ]. …”

“…Size distribution processor (SDP) analysis: ultrasound time (US): 5 min (20 kHz, RT); rest time after US: ~24 h [ 26 ].…”

Dynamic light scattering and transmission electron microscopy in drug delivery: a roadmap for correct characterization of nanoparticles and interpretation of results

“…Filtering samples from large dust particles critically affects the correlation function and improves the agreement between DLS and TEM results. 19,20 Currently, there are several types of commercially available filters (PTFE, PVDF, PES, Nylon) that can be used to remove dust from solutions. Before filtering the solution, it is important to make sure that the filter does not interact with the solvent.…”

Design of Redispersible High-Drug-Load Amorphous Formulations: Impact of Ionic vs Nonionic Surfactants on Processing and Performance

“…The ζ-potential is measured by beam shift from laser Doppler electrophoresis calculated from electrophoretic mobility (correlated with velocity and electric field strength). 43 2.6.2. Filtrate Potency Assay (FPA) for PSD.…”