Hydrodynamic Size Measurement of Polydisperse Sub-Micron Particle Suspensions by Dynamic Light Scattering

Topics Covered

Introduction
W130i Dynamic Light Scattering System from Avid Nano
Sample Preparation & Measurement
Experimental Results
Summary
About Avid Nano

Introduction

Avid Nano's W130i dynamic light scattering system and i-Size™ software provides a quick, convenient and accurate measurement of hydrodynamic size of sub-micron particles and molecules. This technical note illustrates the capability of discriminating a polydisperse suspension of latex particles with a relatively small size differential.

W130i Dynamic Light Scattering System from Avid Nano

The W130i dynamic light scattering system is a breakthrough, high sensitivity instrument for size and molecular weight measurement of proteins, bio-molecules and sub-micron particles. The W130i combines ultimate measurement performance with an economical benchtop footprint, rugged durability and supreme user convenience. It's extraordinarily compact dimensions are the result of miniaturized 'diamond geometry' S.A.B.Re fibre optic technology.

Figure 1. W130i DLS System from Avid Nano

Sample Preparation & Measurement

A mixture of approximately 100 parts 20nm to 1 part 100nm diameter latex particle size standards was dispersed in a phosphate buffer. The dispersion was then measured twice by the W130i for a total of 100 seconds for each measurement.

Figure 2. Intensity distribution of the latex suspension obtained by dynamic light scattering

Experimental Results

The resulting size distribution reported by i-Size indicates two separate peaks of 21nm and 102nm. In Table 1, Peak 1 (20nm) scatters one third of the measured light intensity while peak 2 (100nm) scat-ters the remainder. The % Mass column of the table indicates the smaller size contributes about 97% of the material mass.

Table 1. Particle size distribution data obtained by dynamic light scattering

Pk Mn. Dia. Pos. Dia. Polydisp. % Int. % Mass
1 21.47nm 20.02nm 26.91% 34.05% 97.17%
2 102.80nm 108.03nm 31.57% 65.95% 2.83%

Summary

The W130i DLS system and i-Size software can be used to discriminate a polydisperse sample with a size differential of as little as 5:1, however the size groups must be unequally proportioned in favour of the smaller size by mass (number) to produce similar proportions of scattered light.

About Avid Nano

Avid Nano produce the most exciting and innovative new dynamic light scattering products. Avid Nano pursue the highest levels of performance, know-how, technology, convenience and reliability for all our products, used in laboratory applications requiring fast, accurate DLS measurements in the nano-metre size range.

This information has been sourced, reviewed and adapted from materials provided by Avid Nano.

For more information on this source, please visit Avid Nano.

Date Added: Dec 14, 2012 | Updated: Jun 11, 2013
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