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Particle Size Summary

• Particles dispersed in a liquid undergo Brownian motion. • Brownian motion depends on temperature, viscosity and the size of

the particles. • Smaller particles move faster, larger particles move more slowly. • The Litesizer 500 measures the speed of the particle motion by light

scattering. • Turbid or strongly scattering samples are usually measured at 175°

(back-scattering). Dilute or weakly scattering samples are usually measured at 90° (side-scattering). – The Litesizer 500 offers the possibility to measure at both angles.


Zeta Potential Summary

• The zeta potential depends on the properties of the particle and the surrounding liquid.

• At the isoelectric point, the zeta potential is zero and the colloid may be unstable.

• Charged particles move in an electric field towards the oppositely charged electrode.

• ELS measures the particles’ speed in an electric field (= electrophoretic mobility).

• Zeta potential is determined from the electrophoretic mobility via the Henry equation.

• For aqueous samples, the Smoluchowski approximation is appropriate. • The Litesizer 500 uses cmPALS which is a patented further development of

PALS.


Molecular Mass Summary

• The intercept of the Debye plot is used to determine the molecular mass and the slope is used to calculate A2, the second virial coefficient.


Transmittance Summary

• The user gets instant insight into the suitability of the sample for light-scattering measurements. In addition, it allows the Litesizer 500 to select the best measuring parameters for the particle size measurement of your sample (measurement angle and focus position).


Transmittance measurement mode 3 measurement angles in 1 instrument Intuitive Software & automatic modes Highly sensitive optical bench with robust casing

better resistance against vibrations and no influence by dust, & temp. fluctuations

cmPALS - fast ELS measurement The Ω-cuvette Very short warm up time for the laser

6 min

Litesizer 500 – Features


Cell offers a high quality optical window Electric field can be applied as the electrodes are in contact

with the sample. Cell fits into standard sample holder. Offers a large electrode distance (50mm), which is needed for

aqueous solutions. Offers the possibility to be used in flow through mode for use

with dosing unit. Made of an inert cell material (polycarbonate). Due to the straight part of the Omega shape there are no

gradients of electric field within sample channel!

The Omega Cuvette


Electrophoretic light scattering determines the velocity of the particle movement by measuring the Doppler shift. However, not only are the shift frequencies too small to be measured directly. But also, their direction (positive or negative) cannot be determined. Therefore, a frequency modulator is used. The modulator causes a controlled Doppler shift at the frequency of the reference light. The measured Doppler shift is then the sum of the Doppler shift induced by the modulator plus the Doppler shift induced by the motion of the particles.

In this way, the size and the sign of the Doppler shift, and therefore the zeta potential, can be measured.

Electrophoretic Light Scattering (ELS)


PALS analyzes the rate of phase change of the measured interference between light scattered by the sample and the modulated reference beam. In this way, PALS greatly improves the sensitivity of ELS measurements.

Phase Analysis Light Scattering (PALS)

The method is, however, restricted to modulators with small movements and accordingly short measuring intervals.


The newly patented Anton Paar method, cmPALS is a further development of the classical PALS method. An additional modulator monitor is implemented, which can exactly determine the Doppler shift caused by the modulator. Therefore the measurement is not at all affected by non-linearities of the modulator, which offers the possibility to use modulators with large movements with large movements (despite their non-linearity). The result is that the sensitivity and stability of laser Doppler electrophoresis measurements can be further enhanced. Therefore, with cmPALS, measurements with shorter duration and with lower electric field applied become feasible.

Continuously Monitored PALS (cmPALS)

Monitor Detector



Monitor Detector

Additional detector for monitoring the modulator and determine its Doppler shift. Makes measurement independent of modulator non-linearities. Possible to use modulators with large move. ⟹ Higher sensitivity and stability of the

measurement of the frequency shift.


Additional detector for monitoring the modulator. Makes measurement independent of modulator non-linearities. Possible to use modulators with large move.

EP2735870 (granted 02/2015)

US2014144780 (Pending)



Anton Paar Application notes


Software Kalliope – Measurement Screen


Software Kalliope – Analysis Screen


Litesizer 500 - Configuration Basic Configuration

Mat. No. Name

155761 Litesizer™ 500

155764 (or 166281) Module BM10 (or BM20)

166116 Kalliope™ Professional (software)

Brochure Supplement - Amazon Web Services€¦ · Brochure Supplement . 15.01.15 | Sheet 2 Relevant...

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