Identifying three different particle sizes in one sample with DLS

Particle suspensions often contain more than one size of particle. However, many particle analyzers cannot resolve particle mixtures, instead they detect an average of all sizes. The Litesizer™ 500 can detect three sizes in one sample.

How many different particle sizes are in my sample?

Particle size and size-distribution ranges are specially designed for materials to meet their end-use requirements. For example, in medical applications, particles must be the right size to pass through vessels or cell walls. More than one particle size in such a sample may show the presence of contaminants or aggregates, which can pose a serious health risk.

For coatings such as polymer latexes, on the other hand, the presence of more than one particle size can improve the viscosity, which has a great impact on how the coating is applied.

Thus, it’s important to know what particle sizes are present in a sample. Dynamic light scattering (DLS) is a convenient and non-destructive way to measure particle sizes. Distinguishing even two particle sizes in one sample is challenging, detecting three different sizes is extremely difficult.

How Anton Paar can resolve three particle sizes in a sample by DLS

The Litesizer™ 500 measures particle size, as well as zeta potential and molecular mass by light-scattering technology. Sophisticated algorithms in the Litesizer™ 500 in combination with careful sample preparation enable such particle size resolution.

Polymer  latex  with  three  different  particles:  A  suspension  of  polymer latex particles of sizes 22, 100 and 700 nm was measured by DLS with the Litesizer™ 500, giving the following size distribution.

Such resolution is unprecedented in DLS. Most other DLS instruments would show just one, or at most two broad peaks.

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The Litesizer™ 500’s software displays everything on one page, so you can see your input, measurements and analysis at the same time.