PubMed · 14814946
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P ALEXANDER. 1951. Emulsification with acoustic waves.. https://pubmed.ncbi.nlm.nih.gov/14814946/
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The accuracy of the recently reported low-resolution NMR method (Goudappel, G. J. W.; et al. J. Colloid Interface Sci. 2001, 239, 535) for the determination of drop-size distribution in oil-in-water emulsions is evaluated by comparing the NMR results with precise data from video-enhanced optical microscopy. A series of 27 soybean-oil-in-water emulsions, differing in their mean drop size, polydispersity, oil volume fraction, and emulsifier, is studied. Soybean oil is selected as a typical component of food emulsions. The experimental error of our optical procedure for drop-size determination is estimated to be around 0.3 microm, which allows us to use the microscopy data as a reference for the mean drop-size and distribution width of the studied emulsions, with known experimental error. The main acquisition parameters in the NMR experiment are varied to find their optimal values and to check how the experimental conditions affect the NMR results. Comparison of the results obtained by the two methods shows that the low-resolution NMR method underestimates the mean drop size, d33, by approximately 20%. For most of the samples, NMR measures relatively precisely the distribution width (+/-0.1 to 0.2 dimensionless units), but for approximately 20% of the samples, larger systematic deviation was registered (underestimate by 0.3-0.4 units). No correlation is found between the emulsion properties and the relative difference between the microscopy and NMR data. Possible reasons for the observed discrepancy between NMR and optical microscopy are discussed, and some advantages and limitations of the low-resolution NMR method are considered.
The objective of the present study is to prepare directly compressible powders, containing a poorly water-soluble drug dissolved in medium-chain triglycerides (MCT), by spray drying o/w-emulsions in a pilot plant spray dryer. In addition to the lipid phase, the emulsions contained a water-soluble carrier (a sugar), a water-insoluble carrier (magnesium alumino metasilicate) and a combined emulsifier and film-forming agent (gelatine). A factorial design was used to investigate the effect of formulation variables on the spray drying process and powder properties. The factors varied were soluble carrier type (trehalose or mannitol), insoluble carrier particle size distribution (granular or fine powder) and amount of lipid phase in the emulsion (low or high). Compressibility and compactibility of the spray-dried emulsions were mainly affected by the content of lipid in the powders and decreased on increasing the amount of lipid. Increasing the particle size of the insoluble carrier decreased spray drying process yield and lipid encapsulation efficiency whereas compactibility and handling properties were improved. Incorporation of a soluble carrier becoming amorphous on spray drying resulted in tablets with an increased mechanical strength compared to powders containing a crystalline soluble carrier.