Malvern Zetasizer Nano Series, Руководство пользователя

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Adding PALS and what is it?
PALS ( P hase A nalysis L ight S cattering) is a further improvement on traditional
Laser doppler velocimetry and the M3 implementation described above.
Overall the application of PALS enables accuracy of the measurement of low
particle mobilities. This can give an increase in performance of greater than 100
times than that associated with standard measurement techniques.
This allows the measurement of high conductivity samples, plus the ability to
accurately measure samples that have low particle mobilities. Low applied voltages
can now be used to avoid any risk of sample effects due to joule heating.
How PALS works
By doing a phase comparison of the generated signal with that of a reference
frequency - the reference frequency being that of the
optical modulator - it is
possible to see very small shifts (or displacements) in a particles movement that
would otherwise be concealed due to natural Brownian motion.
As electroosmosis is insignificant due to the implementation of M3 then the
phase between the two frequencies will be constant, so if there is any particle
movement then this phase relationship will alter. Detection of a phase change is
more sensitive to changes in mobility, than the traditional detection of a
frequency shift.
Electrophoretic mobility and consequently the Zeta potential is then
determined by summing the phase shifts measured during the FFR part of the
measurement.
C H A P T E R 1 5 Z e t a s i z e r N a n o S e r i e s
P a g e 1 5 . 1 0
M A N 0 3 1 7
Electrophoretic mobility distribution
Phase plot
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