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Conclusion
Dynamic light scattering appears to be most effective when the line width is large compared to the resolution of the detecting equipment. DLS is less accurate for large spheres and for very viscous fluids where the half width is less than about 50 hz. These problems could foreseeably be circumvented by using better equipment and techniques. The very low frequency noise was a problem throughout the experiment, and its origin is unknown. If the low frequency noise is inherent to the technique and not a flaw in the equipment, then DLS might have an absolute limit in the range of measurable values. According to [1] some commercial machines are capable of measuring particles ranging in diameter from 6μm to 6nm. The results of this experiment followed the theory well. Dynamic Light Scattering proves to be a quick and effective measurement for processes which do not require a great deal of accuracy. Viscosities were successfully measured for all five liquids, using multiple sphere sizes. The 1053nm sphere produced unreliable results. Future students would do well to investigate the use of the CONTIN algorithm to further expand the capabilities of DLS.
[1] A Primer on Particle Sizing Using Dynamic Light Scattering. Mattison, Kevin, Morfesis, Ana and Kaszuba, Michael. 2003, American Biotechnology Laboratory, pp. 20-21.
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