A whole new concept..... Unique to Brookhaven!
For the difficult cases
For measurements of very low mobilities, the Brookhaven
ZetaPALS is the answer. The only answer! With concepts developed
at Bristol University and Brookhaven Instruments, the ZetaPALS determines
zeta potential using Phase Analysis Light
Scattering: A technique that is up to 1,000 times more
sensitive than traditional light scattering methods based on the shifted frequency
spectrum.
Electrostatic repulsion of colloidal particles is often
the key to understanding the stability of any dispersion. A simple, easy
measurement of the electrophoretic mobility even in nonpolar liquids yields
valuable information. Measurements made in water and other polar liquids
are easy and fast with the Brookhaven ZetaPlus . Such measurements cover the range of typically 6 - 100 mV,
corresponding to mobilities of 0.5-8x10-8 m2
/Vs. The ZetaPALS covers this full range, of
course, and extends it by a factor of 1000 in sensitivity!
Principles of Operation
The ZetaPALS utilizes phase analysis light scattering
to determine the electrophoretic mobility of charged, colloidal
suspensions. Unlike its cousin, Laser Doppler Velocimetry (LDV) (sometimes
called Laser Doppler Electrophoresis (LDE)), the PALS technique does not
require the application of large fields which may result in thermal
problems. Because in the measurement of phase shift, the particles need
only to move a fraction of their own diameter to yield good results. In
salt concentrations up to 3 molar and with electric fields as small as 1 or
2 V/cm enough movement is induced to get excellent results. In
addition, the Autotracking feature compensates for thermal drift.
Simple clear presentation
The screen image above shows the results of an actual
experiment with a ZetaPALS instrument. The important parameters and results
are seen at a glance. The excellent agreement of the five runs in this
experiment is obvious as is the match of experimental curve (red) and itnulls
parametrized version (black). As with all Brookhaven instruments the user
can simply produce a customized report using the supplied color printer.
Something more challenging
Of course the ZetaPALS can quickly and easily yield
results from all "regular" samples but its real strength is in
the difficult cases and to demonstrate the performance of this premium
instrument where others fail we offer the following table.
Electrophoretic Mobilities Determined with the
ZetaPALS (units 10 -8 m 2 /Vs)
|
Sample
|
PALS
Result
|
Lit.
Value
|
Comments
|
|
NIST 1980
|
2.51 0.11
|
2.53 0.12
|
Electrophoretic
mobility standard.
|
|
Blood Cells
|
-1.081 0.015
|
-1.08 0.02
|
Dispersed in
physiological saline
|
|
Fe 2 O 3
|
0.013 0.0015
|
N.A.
|
Dispersed in
dodecane
|
|
TiO 2
|
0.255 0.010
|
N.A.
|
Dispersed in toluene - not dried
|
|
TiO 2
|
0.155 0.011
|
N.A.
|
Dispersed in
toluene - dried
|
|
TiO 2
|
-0.503 0.0015
|
N.A.
|
Dispersed in
ethanol
|
|
Casein
|
-0.025 0.002
|
N.A.
|
Dispersed in
PEG - viscous
|
|
SiO 2
|
-0.73 0.04
|
N.A.
|
Dispersed in 2.0 M KCl - High salt
|
Aggressive solvents such as DMF, THF, DMSO, MEK etc are easily accommodated by the
BIC ZetaPALS system with the use of our special solvent resistant
electrodes and glass sample cells. The extension of zeta potential
measurements into the realm of such systems is just another standout
property of the BIC ZetaPALS.
Additional Capabilities
Of course every ZetaPALS system also contains a
complete ZetaPlus
system and this has the special ability to characterize
multimodal zetapotential distributions if they exist.
The ZetaPALS instrument is also available with the full
capability of our 90Plus particle sizer and this
combination instrument provides a benchtop particle characterization center
of great power.
|