Is 10,000 particles the detection limit? Is 0.001 mol/L the lowest concentration for DLS to detect?
The sensitivity of a DLS instrument will depend greatly on the size of your particles, as the scattering intensity is proportional to the 6th power of the particle radius, meaning you will therefore need much lower concentrations of larger particles to measure a comparable signal to from smaller particles.
For reference the Malvern Zetasizer which uses DLS to measure particle size is sensitive to concentrations as low as 0.1ppm.
The sensitivity of a dynamic light scattering setup is very dependent on
- particle size
- optical properties of particles (refractive index)
- optical configuration of the system (scattering angle, scattering volume, laser power, detector type)
For the Zetasizer you can download the software and predict the count rate of a sample for a particular optical configuration [Tools-Calculators-Concentration Utilities]. This can then be used to model the sensitivity of your specific particles. For example for 20nm radius latex particles even 0.0001% by volume scatter enough light for detection, and would correspond to more than 20,000 particles in the scattering volume. For larger or smaller particles the numbers will vary over orders of magnitude.
http://www.materials-talks.com/blog/2015/03/09/how-to-get-the-latest-software-for-the-zetasizer-nano/
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