Coating Coulter Counter

Monodispersed polystyrene sols are used as calibration standards for electron microscopes, light scattering photometers, Coulter counters, particle sieves, etc. Monodispersed silica is used for antireflection lens coatings. Monodispersity (even at a modest level) can usefully be exploited in photographic film, magnetic devices, pharmaceutical preparations and catalysis. 

Photo-crosslinkable monomer containing predissolved initiator, colorless dye precursor, and other necessary ingredients was emulsified in water and then encapsulated. The capsule slurry was machine coated on paper and dried to form a uniform layer of approximately 12 jum thick. The average capsule size was estimated to be 8 m by Coulter Counter. 

Droplet Size Droplet size was determined on a Van tan Coulter counter (Model 4000, Zymo Instruments, India) after diluting the multiple emulsion 100 times with an external phase. The droplet size ranged from < 1.0 to 1.93 pm. Table 9.1 shows the droplet size and the polydispersity of the multiple emulsion formulations. The particle sizes of 6-MP loaded, coated, and uncoated multiple emulsions was nearly the same. The mean diameter of PEG-coated multiple emulsions was found to decrease with time, and it reached its minimum size after 6 to 8 hours. The size was reduced by nearly 15%, and the polydispersity was decreased from 0.18 to 0.09. Kim et al. (1995) found the separation of the aggregated multiple emulsion droplets to occur over several days of equilibration. In our case, it was few hours because of steric stabilization of individual particles surface coated (Vanderhoff and El Asser, 1988). 

Size and Morphology of Liposomes. The size of the particles was determined light scattering (Coulter particle counter). Morphology of the particles was determined by transmission electron microscopy (TEM) using a Zeiss EM-10 microscope. A drop of each dispersion was dried on a carbon coated copper grid and then stained with 2 % aq. phosphotungstic acid. 

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