Influence of refractive index differences on the signal strength for Raman-spectroscopic measurements of double emulsion droplets

The refractive indices of the inner and outer water phases are varied, while the refractive index of the oil phase is kept constant. In order to evaluate the signal of the inner water phase the same amount of tracer is present in all inner phases. For individual phase boundaries of single droplets, the refractive index matching plays a minor role.

However, if there are many droplets with correspondingly numerous phase boundaries, which leads to multiple scattering during the measurement, the matching has a significant influence on the signal strength of the inner phase. When measuring double emulsions, the phases should always be matched if possible, as this results in higher signals. This in turn improves the sensitivity of the measurement.