Electrophoretic properties of emulsions for parenteral nutrition determined by laser light scattering and application of the amplitude-weighted phase structure function (AWPS)

Abstract

Analysis of laser light-scattering signals by the recently developed amplitude-weighted phase structure function method (AWPS) was used to assess the interaction of mono-, di-, and trivalent cations with parenteral fat emulsions. For the investigation of electrolyte-containing fat emulsions possessing low ζ potentials, AWPS has some advantages compared to laser Doppler anemometry. It is more sensitive for the determination of low ζ potentials, uses lower field strengths, and measures the particle size simultaneously. The affinity of the ions for the emulsion droplets was found to increase with their valency. Di- and trivalent ions having a high affinity for the particle surface reduced the potential to zero and even led to a charge reversal, in contrast to monovalent ions. However, no major differences in affinity could be detected for ions of the same valency (e.g., Ca 2+ , Mg 2+ ). The attention paid to calcium as the stability-determining ion in emulsion—electrolyte mixtures for parenteral nutrition should better be directed toward the total content of divalent ions.