Summary: Dynamic Light Scattering (DLS) Manual
Krystyna Brzezinska (email@example.com)
1. Turn ON laser, water bath and filter. Wear safety goggles. 20 min warm-up laser. Block with
cardboard when warming up or changing sample. Block for safety reasons and because it prevents a
flash of very intense light from damaging the photo-cathode whenever the cell is changed.
2. Dusty liquids limit the reproducibility of results. Dust distorts the baseline, artificially broadens the
distribution, may act as a local oscillator, and give rise to number fluctuations. These effects change
completely the model used to fit the correlation function. Dust is primarily a problem in highly polar
liquids, especially water.
3. Sample preparation consists of three parts: solvent purification, cell cleaning, and
solution/suspension preparation. The last part depends on the particular type of sample. Only general
guidelines can be given. The solvent has to be free of trace organic impurities, and filtered. Residual
metal ions may affect the chemistry, motion, or the shape of the molecules or particles of interest. In
addition to the above effects, trace organics may significantly alter the surface tension of the primary
solvent. Trace organics are removed by distillation or absorption. Finally, removal of dust by filtration
greatly increases the repeatability of DLS measurements.
4. Cells: Order from Brookhaven Instruments: N.Y., fax: 631-758-3255 (phone: 631-758-3200). Round
glass sample cell, 12mm O.D., min vol. 1.5mL, PE cap # BI-RC12 (unit price ~ $6.00).
5. Cell cleaning: The degree of cell cleaning depends on the application.