How does DLS work in the Zetasizer microV?
Written by: Ulf Nobbmann
Dynamic Light Scattering (DLS) is also known as Quasi Elastic Light Scattering (QELS) or Photon Correlation Spectroscopy (PCS) and it has been well-known for a quite a while now.
In this post, I’d like to point you to a presentation which was recorded several years ago, where I refer to the generic Zetasizer, and the same concept holds true in the more recently developed Zetasizer µV.
What is different in the microV?
As well as being a batch instrument, it is also designed to be used as a detector in conjunction with your existing chromatography system, either a system from our Viscotek product line, or an Agilent, an Akta, Waters, or even a custom-built system you designed in your lab. As long as an analog concentration signal output in mV from the refractive index (RI) or the ultraviolet (UV) detector can be fed into the OmniSEC software, the molecular weight can be plotted versus elution volume.
In the 4 minute DLS primer below, a few slides of theory are combined to explain how intensity fluctuations due to the Brownian motion / diffusion are analyzed to find the diffusion coefficient of the scattering molecules. This is based entirely on physics and does not require any calibration or reference standards. The scattering vector (which entails the refractive index n of the solution, the scattering angle θ, and the wave length λ of the laser) is all we need to know (well, aside from the Boltzmann constant, the temperature, and the viscosity η of the solution).
The use of dynamic light scattering and associated publications have really expanded in the last decade, and there is still a range of applications and broad use left to discover: combining DLS with separations systems.
- Technical Note: Connecting the Zetasizer MicroV to any SEC System
- The definite guide to Malvern GPC/SEC information
- Biophysical Characterization: Questions and Answers
- 5 Steps to improve SEC-LS data