Very often in the study of aqueous solutions it is necessary to check the purity of distilled water. Its purification from impurities, especially when light scattering is very important. How can you check the purity of water with the help of dynamic light scattering devices?
This water purity study will use a newly developed instrument called dynamic light scattering device (DLS) to examine water purity. Dynamic light scattering (DLS) services for the measurement of particulate size distribution and for monitoring aggregation of proteins in solution or suspensions. Size and particle size distribution of particulate samples are essential parameters, and their ongoing, accurate monitoring ensures product consistency. High throughput DLS is used by our experts in routine studies of particles in solutions, dispersed systems, and biologics, such as proteins, in solution, water purity. The instrument can perform a combination of the three most important parameters for the colloid and polymer chemist
Static light scattering, i.e. the average intensity of scattered light is a much more appropriate method for checking the purity (= lack of particles, here) than DLS. All DLS instruments give this parameter, but a much simpler way is to use a nephelometer, such as those sold by Hach.
In clean rooms for microelectronics, where every stray particle is a problem, special particle counters are used to check water purity.
@ Yuri Mirgorod I did see this question in another posting (Easy-in-preparation samples for practice in DLS measurements) but felt I couldn’t offer much here. The purity of water is normally assessed by some form of conductivity measurement but this often does not take into account any organic contamination. As Alan Parker points out, an obscuration counter is normally used in industries such as the semiconductor one to look at particulate contamination (typically in the 1 – 100 um region). The only (poor?) way I could see a DLS instrument being used is to first confirm that the attenuator is in the widest position (11 on the Malvern Zetasizer) indicating no perceptible signal (i.e. no gross contamination). Then one could observe the count rate (photons) directly and any ‘kick’ in this may indicate the passage of a large or sedimenting particle. However, this means that the cleanliness of the cuvette or any other device used to contain the sample is paramount. I assume too that one is working in a Class 100 environment or, better still, remotely. I’m ignoring ‘work’ where researchers claim to be able to influence the structure of water (and the DLS correlogram) by thought alone… For example, L N PYATNITSKY, V A FONKIN “Human Consciousness Influence on Water Structure” Journal of Scientific Exploration, Vol. 9, No. 1, pp 89-105, (1995)
But what about the maximum particles size can be detected by DLS Dr. Prem Baboo
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