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Theory Answers
How does separation work in Gel Permeation Chromatography?
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Nanoparticle and Protein Sizing
Viscotek is proud to introduce its range of Dynamic Light Scattering Detectors featuring rapid, accurate and sensitive sizing for proteins, biomolecules, nanoparticles & polymers and a pair of outstanding technologies unique to Viscotek.
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"The service provided by Viscotek representatives is unmatched by any other in the industry... A wonderful addition to the polymer community."
- E.F, Ph.D., Academic Institution
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"The GPCmax and Triple Detector System is state-of-the-art while remaining affordable and easy to use."
- M. G., Ph.D., Academic Institution |
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DLS Theory - Overview |
 Dynamic light scattering (DLS - also known as Photon Correlation Spectroscopy) is a powerful technique, which can be used to determine the size distribution of small particles in solution. It
works by measuring the speed at which particles move under Brownian motion.
There are several key challenges that need to be overcome for optimal DLS operation:
Concentration - Applications cover a wide range of concentrations,
and dilutions are often impossible
Sample Volume - In Protein chemistry, samples are very precious
and using only a tiny amount in an experiment crtitical
Sensitivity - The physics and mathematics behind DLS are very demanding
and the process of calculating the correct size distribution relies heavily on good
data. It is important to have maximum resolution for accurate results.
 To overcome the concentration
issue, Viscotek invented Dual Attenuation Technology where simultaneous digital
control of laser power and optical attenuation produce unprecedented dynamic range
from 100% to 0.0001% transmission. This allows the instrument to automatically operate
at the optimum settings for every sample, even concentrated solutions, without user
intervention.
The Sample Volume concern is only solved by the use of clever optical
arrangements allowing for a very small sample cell. Viscotek's
model 802 is able
to operate as little as 2ul of sample.
To maximize sensitivity, Viscotek incorporates a 544 multi-tau
auto correlator in both the Horizon and model
802 DLS instruments, which greatly
improves the accuracy of results over those obtained by the more common 255 channel
autocorrelator. This specifically improves the horizontal resolution of the auto-correlation
function.
Most importantly, Viscotek uses patented Single Mode Fiber (SMF) technology in the
optic of the Horizon and model 802.
The SMF acts as an optical filter, eliminating
extraneous signals and only allowing a single mode of scattered light to reach the
detector. The result is the cleanest signal, enabling high sensitivity and precise
size distributions. The latter being essential for protein crystallography studies. |
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