An alternative way to analyze quasi-elastic light scattering data for broadly distributed samples |
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Authors: | C Wu |
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Institution: | (1) Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong |
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Abstract: | In Quasi-Elastic Light Scattering (QELS), an apparent average hydrodynamic radius
can be calculated from the measuredz-average translational diffusion coefficient D
z
by using the Stokes-Einstein equation:
withk
B,T and being the Boltzmann constant, the absolute temperature and the solvent viscosity, respectively. It is known thatR
h, app is not the same as R
h
z
because
, especially when a sample is broadly distributed. In order to obtain R
h
z
instead ofR
h, app, an alternative way to analyze QELS data is proposed: at first, we manipulate the measured correlation functionb
1/2|g
(1)(t)| into a new function
; and then, we can analyze this new function to obtain an apparent parameter Dapp and an apparent distribution width
. We have shown that no matter how broadly a sample is distributed, Dapp can be easily reduced to R
h
z
, and
is directly related to the distribution width. In this report, besides using a simulated time correlation function, we also used two measured correlation functions of a latex dispersion with a broad particle size distibution and a polystyrene standard with a broad molecular weight distribution to demonstrate this alternative way. |
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Keywords: | QELS DLS hydrodynamic size polydispersity data analysis |
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