This article explains how scattering signals from buffer additives may influence the outcome of dynamic light scattering measurements. A buffer does not only compensate for changes in the pH, but often contains additional substances, such as sugars or detergents, required to stabilize the molecule of interest.

Sugars and detergents scatter light like any other particle. While sugars are typically quite small (usually less than 1-2 nm), detergent micelles can vary drastically in size. DLS measurements do not discriminate the types of particles they detect light scattering from, so DLS measurements on Prometheus Panta will be sensitive to sugars and detergents.

While there is no formal method in Prometheus Panta to subtract the background scattering from excipients such as sugars or detergents, it is possible to perform DLS measurements with blank buffers to determine the scattering profile and size of particles in the buffer to use as a background comparison for the sample measurement.

If scattering from buffer components influences the outcome of a DLS experiment (visible as a shifted cumulant radius or additional buffer peaks in the size distribution), rely on the results from the size distribution fit to report particle sizes. For more information on which fitting model to choose. Another possibility to solve this issue is increasing the concentration of the dissolved particles.

For analyses of the diffusion interaction parameter kD, it is possible to filter out the contribution of small particles to the output diffusion coefficient by applying a lower cutoff to the radius and thereby to the diffusion coefficient.