Welcome To Dynamic Light Scattering

explanation of dynamic light scatteringMeritics warmly welcomes you to the Dynamic Light Scattering site, which we have set up to bring you news, views, background information and – above all – impartial, expert advice on this important subject.

As you know, for anyone involved in characterisation of materials, the choice of techniques and equipment is vast and can be quite confusing. Our aim is to clarify those choices and help you make the ideal selection for your situation.

Let’s begin by clarifying what dynamic light scattering is. Sometimes referred to as photon correlation spectroscopy, it is a technique often used for measuring the size – and size distribution – of small particles held in suspension, or polymers held in solution. It is also useful for investigating the behaviour of concentrated polymer solutions and other complex fluids.

In simple terms, the photon correlation spectroscopy method works by shining a light on a sample of the liquid. When the light hits the small particles it scatters in all directions. Time-dependent fluctuation in the scattering intensity is caused by Brownian motion of the particles, which results in constant change in the distance between particles. Analysis of the fluctuation yields information on the size of those particles.

A related method is electrophoretic light scattering. In this case it is an oscillating electric field rather than Brownian motion that causes the particles to move. It is used to measure electrophoretic mobility, from which zeta potential can then be calculated.

Zeta potential may be described as the potential difference between a dispersion medium and the stationary layer of fluid attached to a dispersed particle. It gives a useful indication of the effective charge in solution.

For analysis using photon correlation spectroscopy, a submicron particle size analyser is needed. This will measure particle size in the range from 0.6 nm to 7 µm. Analysis requiring electrophoretic light scattering involves zeta potential analysers. These will calculate zeta potential of particles in a size range from 0.6 nm to 30 μm.

Some of the dynamic light scattering products developed by Beckman Coulter® combine both methods in the same instrument. A variety of standard and optional cells are used, along with the extra option of an auto-titrator. They can handle both aqueous and non-aqueous samples, with particle concentrations ranging from 1 ppm to 40% (w/v).

To find out what these instruments can do, in more detail, please explore this site further and let Meritics help you find the answer.

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