Dynamic Light Scattering (DLS)
Dynamic Light Scattering (DLS), or Photon Correlation Spectroscopy, is a non-invasive, fast, and precise technique used to measure the size of particles, emulsions, and molecules (typically 1 nm to 10 µm) in suspension. It measures Brownian motion—the random, solvent-induced movement of particles—using laser light scattering to determine their hydrodynamic size. Key applications include protein stability analysis, nanoparticle formulation testing (liposomes, micelles), pharmaceutical research, and quality control for cosmetics and food emulsions.
Ideal Uses of DLS
- Pharmaceutical & Biopharmaceutical Development
- Nanotechnology & Drug Delivery
- Material Science & Polymer Characterization
- Environmental & Colloidal Analysis
Strengths
- Measurements are very fast, typically providing data in less than a minute
- Only small sample volumes are needed, often as low as 2mL
- DLS is exceptionally sensitive to the presence of small amounts of aggregates. Because large particles scatter light much more intensely than small ones, it can detect even trace amounts of aggregation
- The sample remains in its native state and is fully recoverable for further, different types of analysis
Limitations
- Because large particles scatter significantly more light, even a tiny amount of aggregates or dust can skew results and mask the presence of smaller particles.
- DLS struggles to distinguish between populations of similar sizes, requiring a difference of at least a factor of 3 in size to resolve them properly. It is best suited for monodisperse samples.
- High-concentration samples cause “multiple scattering,” where light scatters off multiple particles before reaching the detector, resulting in inaccurate sizes.
- Samples must be transparent; turbid or highly viscous samples (typically >100 mPa·s) are difficult to measure accurately.
- Results are reported as an equivalent hydrodynamic sphere diameter, which can be inaccurate for rod-shaped or non-spherical molecules.
- DLS provides an intensity-weighted average (often the Z-average) rather than a direct count of particles.
DLS Technical Specifications
- Range: 0.3 nm – 10 μm
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