Characterisation of emulsions

M.L. Johns and K.G. HoUingsworth, Characterisation of emulsion systems using NMR and MRI, Prog. Nucl. Magn. Reson. Spectrosc., 50(2-3), 51-70 (2007). 

Le Denmat, M., Anton. M. and Beaumal, V. (2000) Characterisation of emulsion properties and of interface composition in O/W emulsions prepared with hen egg yolk, plasma and granules. Food Hydrocolhid., 14, 539. 

Ultrasonically assisted extraction is also widely used for the isolation of effective medical components and bioactive principles from plant material [195]. The most common application of low-intensity ultrasound is as an analytical technique for providing information about the physico-chemical properties of foods, such as in the analysis of edible fats and oils (oil composition, oil content, droplet size of emulsions, and solid fat content) [171,218]. Ultrasonic techniques are also used for fluids characterisation [219]. 

At present our understanding of emulsion behaviour is not as well developed as that of particulate or polymer systems. Part of the difficulty in correlating the rheology lies in the high level of characterisation required in order to differentiate between systems as well as the greater difficulty in preparing monodisperse model emulsions than rigid particulate systems. However, this is understandable because emulsion characterisation can be formidable. 

Rowe RC, McMahon J. The characterisation of the microstructure of gels and emulsions containing cetostearyl alcohol and cetrimide using electron microscopy—a comparison of techniques. Colloid Surf 1987 27 367-373. 

Norden, T.R, Siekmann, B., Lundquist, S., Malmsten, M. Physicochemical characterisation of a drug-containing phospholipid-stabilised o/w emulsion for intravenous administration. Eur J Pharm Sci 13 (2001) 393—401. 

Muir, D.D., McCrae-Homsma, C.H., Sweetsur, A.W.M. 1991. Characterisation of dairy emulsions by forward lobe laser light scattering - application to cream liqueurs. Milchwissenschaft. 46, 691-694. 

Unfortunately, most emulsions do not have a single droplet size. There are small, medium and large droplets present, and it is important to be able to characterise the emulsion for this. This is done by counting the number of particles that is smaller than a specific size, for many different sizes. The resulting data can then be plotted on a curve, the cumulative distribution curve. Alternatively, one can count all particles that have a size within an interval of sizes (e.g., 1-2 pm), and do this for all intervals. Plotting all the numbers obtained for all intervals, then results in a frequency distribution. The two distributions are closely related the derivative of the cumulative curve to the particle size, will give a (continuous) curve that is similar to the discrete frequency distribution obtained earlier, and the smaller the intervals are chosen, the closer the derivative will follow the frequency distribution (see Figure 15.4). 

Krajnc P, Leber N, Stefanec D, Kontrec S, and Podgomik A. Preparation and characterisation of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media. J. Chromatogr. A 2005 1065 69-73. 

Pedersen GP, Faldt P, Bergenstahl B, et al. Solid state characterisation of a dry emulsion a potential drug delivery system. Int J Pharm 1998 171(2) 257-270. 

Jesionowski, T., Characterisation of pigments obtained by adsorption of C.l. basic blue 9 and C.l. acid orange 52 dyes onto silica particles precipitated via the emulsion route. Dyes Pigments, 67, 81, 2005. 

Dairy products represent a different challenge as the extraction of fat is characterised by the formation of fat-protein emulsion and, in the case of cheese samples for example, is plagued by severe interference from casein. Conventional chemistry would prescribe the concurrent use of heat and aqueous alkali solutions (e.g., KOH or NH4OH) to dissolve the protein and to free the fal which can then be separated, collected, washed and dried. Not surprisingly current AOAC methods are based upon such principles. Generally, the samples are heated in presence of alkali solution in solvents such as diethyl ether and petroleum ether. Ethanol is also used to minimise the formation of emulsion, to further assist in breaking up fat-protein interactions, and to precipitate the proteins. 

Samples were also taken from the diluted and the long float. The characterisation of the phase behaviour resulted for both floats in a three-phase state, which, in contrast to the short float, is not located at T = 37°C, but at T = 60°C as shown in Fig. 10.7. At the degreasing temperature T = 30°C now a fat-in-water microemulsion coexists with a fat-excess phase, which is turned into a stable fat-in-water emulsion via shearing. 

R. Miller, V.B. Fainerman, A.V. Makievski, J. Kragel, D.O. Grigoriev, F. Ravera, L. Liggieri, D.Y. Kwok and A.W. Neumann, Characterisation of water/oil interfaces, in Encyclopaedic Handbook of Emulsion Technology , J. Sjoblom (Ed.), Marcel Dekker, New York, 2001, 1... 

Using the HLB system for the characterisation of surfactants, a minimum interfacial tension is observed when the HLBr is reached. Fig. 6.7 shows, as an example, the interfacial tension and the droplet size in emulsions of decane and sunflower oil, respectively, as a function of the HLB. For decane, the minimum y value and the minimum size of emulsion droplets are observed in the region of HLB 9 and for sunflower oil around 11, which corresponds to the required HLB values. Apparently, one of the reasons leading to an increase in emulsion stability when reaching HLBtp is the increase of emulsion dispersity under conditions of the maximum decrease in interfacial energy. 

Serfert Y, Schroder J, Mescher A et al. (2013) Characterisation of the spray-drying behavior of emulsions containing oil drop-lets with a structured interface. Journal of Microencapsulation 30 325-334. 

N. Sultana, M. Wang, Fabrication of HA/PHBV composite scaffolds through the emulsion freezing/freeze-drying process and characterisation of the scaffolds, J. Mater. Sci. Mater. Med. 19 (7) (2008) 2555-2561. 

K. Wesiesen. Development and characterisation of novel intravenous emulsion systems. Arch. Pharm., 324 639, 1991. 

H Kallevik. Characterisation of crude oil and model oil emulsions by means of near infrared spectroscopy and multivariate analysis. PhD thesis. University of Bergen, 1999. 

Bower, C., Gallegos, C., Mackley, M.R., and Madiedo, J.M. (1999) The rheological and microstructural characterisation of the non-linear flow behaviour of concentrated oil-in-water emulsions. Rheal. Acta, 38 (2), 145-159. 

This article will provide a general overview of the emulsion polymerisation process and explain how the resulting latexes are used in industrial applications. An introduction to the basic concepts of emulsion polymers will be given, followed by a description of the various production processes and characterisation methods. The classes of emulsion polymers will be surveyed, and the commercial technologies and potential future uses discussed. A number of comprehensive texts on emulsion polymers are available for more in-depth study (60, 89, 94,95, 364, a.l-a.ll). 

R. J. Hunter, Recent developments in the electroacoustic characterisation of colloidal suspensions and emulsions. CoUoids Surf. A 141(1), 37-65 (1998). doi 10.1016/S0927-7757(98)00202-7 R.J. Hunter, Measuring zeta potential in concentrated industrial slurries. Colloids Surf. A 195(1-3), 205-214 (2001). doi 10.1016/S0927-7757(01X)0844-5 R.W. O Brien, Electro-acoustic effects in a dilute suspension of spherical particles. J. Fluid Mech. 

Millqvist-Fureby, A., 2003. Characterisation of spray-dried emulsions with mixed fat phases. Colloids Surf. B 31, 65-79. 

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