Phase Analysis Light Scattering (PALS)
PALS is a technique for measuring the electrophoretic mobilities of
colloidal particles. It is a technique that is very similar to Laser Doppler
Electrophoresis (LDE).
The sensitivity of the technique is far superior to that which can be
obtained from LDE measurements, and is particularly suited to measurements
of charged particles suspended in nonpolar media (i.e. solvents with much
lower relative permittivities than water).
Below is a schematic of the PALS system we have designed, constructed and currently use in our laboratories.
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PALS
uses a cross-beam technique and offsets one of the laser beams relative to
the other by a couple of kHz. (In this case we use acousto-optic modules,
Bragg cells, to achieve this). Our system is capable of reliable measuring
electrophoretic mobilities down to at least 10-11 m2 s-1 V-1.
The system uses a National Instruments NI-DAQ data acquisition card and a
National Instruments GPIB card to collect the data and control the
experiment. The software that controls the system runs under Windows 95/98
using Delphi as the Rapid Application Development environment.
The system is also suitable for the measurement of aqueous colloidal
systems. We have tested the reliability of the system with respect to a Rank
Bros MicroElectrophoresis apparatus.