Monitoring the Stability of an Emulsion by High-Frequency Spectroscopy

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High-Frequency spectroscopy has been applied to monitoring the stability of oil-in-water emulsions. Emulsion is a kind of colloidal suspension composed of a liquid dispersed throughout another liquid, like oil droplets in water. It was found that stable emulsions showed absorption peaks at around 550 MHz ; further, they shifted from lower to higher frequencies with time. The amount of shift from lower to higher frequencies increased with the stored time. The rate of increase of the frequencies was dependent on the amount of emulsifier added. These results show that the stability of emulsions can be monitored by the amount of the frequency shift.The reason why the absorption peak shifted to a higher frequency region is considered to be because the relative ratio of oil to water increased in the upper layer of the emulsion sample, where the electrode of detecting resonance was dipped.