Emulsions droplet size measurement

The responses chosen all relate to important foam properties. We believed that yi, the emulsion droplet size, determines y2, the cell size in the resultant foam, and we wished to determine whether this is true over this range of formulations. The foam pore size ys should determine the wetting rate y7, so these responses could be correlated, and yg, the BET surface area, should be related to these as well. The density y and density uniformity ys are critical to target performance as described above, and ys, the compressive modulus, is an important measure of the mechanical properties of the foam. 

K. G. Hollingsworth, M. L. Johns 2003, (Measurement of emulsion droplet sizes using PFG NMR and regularization methods),/. Colloid Interface Sci. 258, 383. 

Figure 7.17 Influence of i-carrageenan on the state of flocculation of BSA-stabilized emulsions (20 vol% oil, 1.7 vt% protein. pH = 6, ionic strength = 0.005 M) stored at 25 °C for 40 hours. The average droplet size measured by static light scattering (Malvern Mastersizer), d32, is plotted against the polysaccharide concentration ch added to the freshly made emulsion. Reproduced from Dickinson and Pawlowsky (1997) with permission.

Ultrasonic methods infrared scanning for emulsion stability determination, 597-598 spectrometry, emulsion droplet size determination, 581 velocimetry, to measure fat, 572 Ultraviolet (UV). see also Spectrophotometry protein analysis, CD, 219-243 protein concentrations by... 

A new method for droplet size measurement, using a bench-top pulsed-field-gradient NMR spectrometer operating in the time domain, has been reported (18). The continuous water phase is successfully suppressed by gradient pulses in order to measure the dispersed oil phase. Simulations show that for most common oil/water food emulsions the influence of droplet diffusion is negligible due to a rather large droplet size or a high viscosity of the continuous water phase. 

Emulsion droplet sizes in the range from 1 to 50 jim can be measured with rather modest gradient strengths of about 1 T/m. Note that the size determination rests on measuring the molecular motion of the dispersed phase, so the method cannot be applied to dispersed phases with low molecular mobility. In practice, oils with self-diffusion coefficients above 10 m s is required for sizing of OAV emulsions. Of course, W/0 emulsions with most conceivable continuous media can be sized. 

What distinguishes Y-junctions most from other shear-driven techniques is that the emulsion droplet size can solely be controlled by the continuous phase to predict the droplet size, a simple force balance can be used, linking viscous shear force and interfacial tension, indicating a one-step mechanism [10] (in the future directions, it is described how this feature of Y-junctions may be used to measure dynamic interfacial tensions). This suggests that emulsification in Y-junctions... 

The average droplet size measured as a function of time indicated that neither Pluronic F-68 nor the fluorinated surfactants 1, 2, or 3 alone can produce a stable perfluorodecalin emulsion. The synergism between the two surfactants, Pluronic F-68 and a fluorinated surfactant, is essential for achieving storage stability. 

Figure 9 shows the relaxation time T2 of micelles of sodium dodecyl sulfate (SDS) as a function of SDS concentration [13,16,17], It is evident that the maximum relaxation time of micelles is observed at an SDS concentration of 200 mM. This implies that SDS micelles are most stable at this concentration. For several years researchers at the CSSE have tried to correlate the measured T2 with various equilibrium properties such as surface tension, surface viscosity, and others, but no correlation could be found. However, a strong correlation of t2 with various dynamic processes such as foaming ability, wetting time of textiles, bubble volume, emulsion droplet size, and solubilization of benzene in micellar solution was found [18]. 

Other important characterization techniques include electrophoresis measurements of droplets [11, 12] (see Section XIV-3C), infrared absorption of the constituent species [13], and light or x-ray scattering. NMR self-diffusion measurements can be used to determine droplet sizes in W/0 emulsions [14]. 

A Malvern Mastersizer (Malvern Instruments Ltd, Malvern, UK) with optical parameters defined by the manufacturer s presentation code 0505 was used to determine the droplet size distribution. The measurement was made in triplicate at room temperature. Water was used to disperse the emulsion droplets. 

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. 

Studies of flow-induced coalescence are possible with the methods described here. Effects of flow conditions and emulsion properties, such as shear rate, initial droplet size, viscosity and type of surfactant can be investigated in detail. Recently developed, fast (3-10 s) [82, 83] PFG NMR methods of measuring droplet size distributions have provided nearly real-time droplet distribution curves during evolving flows such as emulsification [83], Studies of other destabilization mechanisms in emulsions such as creaming and flocculation can also be performed. 

Spatially-resolved measurement of the droplet size distribution can be accomplished by the implementation of velocity compensated pulse sequences, such as the double PGSTE [81] in a spatially resolved imaging sequence. Accurate measurements of spatially resolved droplet size distributions during flow and mixing of emulsions would provide truly unique information regarding flow effects on the spatial distribution of droplets. 

G. J. W. Goudappel, J. P. M. van Duyn-hoven, M. M. W. Mooren 2001, (Measurement of oil droplet size distributions in food oil/water emulsions by time domain pulsed field gradient NMR), /. Colloid Interface Sci. 239, 535. 

Particle Size Measurement. The best way to evaluate an emulsion s stability is probably to measure its particle size distribution. A number of methods are available for droplet size determination (see Sec. VIII.A). Optical microscopy, although a time-consuming technique, is a direct way of measuring droplets larger than 1 pm. Nowadays, laser lightscattering, diffraction, and transmission methods are becoming popular for routine determination of particle size [151, 152],... 

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