Emulsions microscopy studies

Dickinson, E. 1989 Surface and emulsifying properties of caseins. J. Dairy Res. 56, 471-477. Goff, H.D., Liboff, M., Jordan, W.K., Kinsella, J.E. 1987. The effects of polysorbate 80 on the fat emulsion in ice cream mix evidence from transmission electron microscopy studies. Food Microstruct. 6, 193—198. 

Goff, H.D., M. Liboff, W.K. Jordan, and J.E. Kinsella, The Effects of Polysorbate 80 on the Fat Emulsion in Ice Cream Mix Evidence from Transmission Electron Microscopy Studies, Food Microstruc. 6 19-198 (1997). 

The topic of ocular bioavailability of indomethacin administered in a sub-micrometer emulsion was al.so examined by the research group led by M, J. Alon.so at the University of Santiago de Compo-stela, Spain (32). These workers tested several carriers in vivo in rabbits nanopaiticles, nanocapsules, microparticles, and a submicrometer emulsion. The latter, prepared by the method of Yu et al. (33) with poloxamer 188 and soybean lecithin and containing 0.1% w/v indomethacin, had particles of diameter 0.21 0.02 im. The submicrometer systems (nanoparticles, nanocapsules, and emulsion) increased by more than three-fold the indomethacin concentration in the cornea, aqueous humor, and iris-ciliary body at 0.S and 1.0 h post instillation. Furthermore, an increased indomethacin bioavailability of 300% was observed in comparison with the value obtained for an aqueous commercial solution. Confocal laser scanning microscopy studies indicated (hat the submtcion particles penetrated into the comeal epithelium cells by endocyiosis (he audiors further suggested that the vehicle components (lecithin in the case of emulsions) may act as penetration enhancers or as endocytotic stimulators. 

Butyl acrylate-methyl methacrylate copolymer latices with a core-shell structure were prepared by a sequential emulsion polymerisation technique. SEM and transmission electron microscopy studies undertaken on the polymer dispersions, powders obtained by spray drying and latices prepared by redispersing the powders in water revealed the influence of polymerisation parameters on the micromorphology of the starting latices, and correlations between the dimensional and micromorphological characteristics of the starting latices, the powders and the redispersed latices. 8 refs. 

Other recent applications of FT-IR in pharmaceutical analysis include reaction monitoring by fiberoptic FT-IR/ATR spectroscopy140 and stability studies of pharmaceutical emulsions using FT-IR microscopy.141 A novel equipment cleaning verification procedure using grazing angle fiberoptic FT-IR reflection-absorption spectroscopy was described by Perston et al.142... 

In a separate experimental study, Aronson and Petko [90] also observed an increase in yield value with increasing salt concentration, for w/o HIPEs. However, the interfacial tension of the emulsions was seen to decrease with addition of a number of electrolytes to the aqueous phase, in contrast to observations made by Pons et al. The reason for this discrepancy is not clear, but may be due to different interactions between the different surfactants and salts used by each group. It is hinted that the increase in yield value on addition of salt, as observed by Aronson et al., is due to a decrease in average droplet size however, this was not examined extensively, and determination of droplet diameters was by optical microscopy only. 

The non-aqueous HIPEs showed similar properties to their water-containing counterparts. Examination by optical microscopy revealed a polyhedral, poly-disperse microstructure. Rheological experiments indicated typical shear rate vs. shear stress behaviour for a pseudo-plastic material, with a yield stress in evidence. The yield value was seen to increase sharply with increasing dispersed phase volume fraction, above about 96%. Finally, addition of water to the continuous phase was studied. This caused a decrease in the rate of decay of the emulsion yield stress over a period of time, and an increase in stability. The added water increased the strength of the interfacial film, providing a more efficient barrier to coalescence. 

Various electron microscopy techniques have been used to study the structures of whippable emulsions such as normal and cryo-scanning electron microscopy or transmission electron microscopy using various preparation methods such as freeze fracturing, freeze etching, etc. The literature is quite extensive, and only a few important papers will be discussed in this chapter. 

Methodologies to assess interface properties of amphiphiles are surface tension measurements (Phan et al. 2006 Golding and Sein 2004 Miller et al. 2004), ellip-sometry (Dickinson 2003a Murray 2002) and Brewster angle microscopy (Grigoriev et al. 2006 Rodrguez Patino et al. 2001). Both and P NMR have been applied in order to study the conformation and dynamics of P-casein at the oil-water interface of emulsions (ter Beek et al. 1996). Their NMR results showed that the protein at the interface has mobile regions with httle secondary structure in which the motions are rather slow. 

Diffusion can be divided into free and restricted diffusion. A combination of NMR diffusometry and microscopy has proved useful for the study of probe diffusion in gels and emulsions (Hagslatt et al. 2003 Loren et al. 2005 Hermansson et al. 2006 Walther et al. 2006) For such studies the probe should be much larger than water so that the obstruction can be clearly observed in NMR difiusometiy. Small molecules... 

Experimental investigations that deal in detail with particle formation in emulsion copolymerization are scarce. Nomura et al. [78] studied the kinetics of particle formation and growth in the emulsion copolymerization of VDC and MMA using NaLS as the emulsifier and KPS as the initiator. The number of polymer particles produced was determined using particle diameters measured by both electron microscopy (TEM) and dynamic light scattering (DLS) for comparison. They found that where Sq and Iq are the initial... 

During the process of three phase foam thinning, three distinct films may occur foam films (water film between air bubbles), emulsion films (water between oil droplets) and pseudoemulsion films (water film between air and oil droplets) (Figure 1). To study the behavior of these films and particularly the oil droplet-droplet, oil droplet-air bubble and oil droplet-foam frame interactions it is necessary to utilize numerous microscopic techniques, including transmitted light, microinterferometric, differential interferometric and cinemicrographic microscopy. 

Both the light microscope (LM) and the confocal scanning laser microscopy (CLSM) operate in the micron range. The advantage of the CLSM is that it allows for measurements of dynamic events such as crack propagation and three-dimensional reconstructions. Moreover, the optical resolution in the CLSM is about 40% better than in the LM. The CLSM also makes it possible to study bulk samples with a minimum of preparation, which is quite important when handling multiphase colloidal structures such as emulsions. 

Sinks BP, Kirkland M (2002) Interfacial structure of solid-stabilized emulsions studied by scanning electron microscopy. PCCP 4(15) 3727-3733... 

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