Introduction to DLS
Dynamic Light Scattering (DLS) is also known as Photon Correlation Spectroscopy (PCS). Typical applications are particle size distribution of small particles such as proteins and peptides, micelles and viruses, organic and inorganic nano-particles and pigments.
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The effect of temperature on particle size and stability can be investigated. The Dynamic Light Scattering instrument at Particle Analytical is a Nano Zetasizer, where both particle size and zeta-potential can be measured:
- Dynamic Light Scattering is used to measure particle and molecule size. This technique measures the diffusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship.
- Laser Doppler Micro-electrophoresis is used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which then move with a velocity related to their zeta potential.
- Static Light Scattering is used to determine the molecular weight of proteins and polymers. In this technique, the scattering intensity of a number of concentrations of the sample is measured, and used to construct a Debye plot. From this the average molecular weight and second virial coefficient can be calculated, which gives a measure of molecule solubility.
Instrument and measuring principles, DLS
|Instrument||Malvern Nano Zetasizer|
|Sample amount||Minimum 12 µL and maximum 3 mL of stable emulsion / suspension|
|Temperatures||From 15 to 40°C.|
|Result||Result given as particle size distribution of stable emulsions and suspensions in the size range 0.3 nm to 10 µm.|
|Requirements||The viscosity of the emulsion / suspension is required as well as the refractive indices of media and sample.|