A comparison of two quality assessment methods for emulsions.

A common method of assessing the quality of emulsions is to evaluate the size distribution of the globules of the internal phase. The primary aim of this work is to compare the sensitivity of this test to an alternative method. The sizes of the globules of two emulsions, an oral emulsion and a total parenteral nutrition (TPN) emulsion, were determined using a light microscope. Globule size analyses were performed upon preparation and during storage of the emulsions. Using a computer program specially developed for this study, the recorded diameters were placed into size groups and the volumes of each of the measured globules was determined. For each size group, the total volume of all the globules within the group and the volume percentage of the oil phase represented by the group were calculated. The volume distribution of the internal phase across the size groups was found to predict emulsion instability better than the globule number distribution and thus is a better determinant of emulsion quality. This technique may have general application in the evaluation of TPN emulsions and other spheres, such as liposomes.