Determination of Acetone in a Water/Toluene Emulsion in Each Phase Using Raman Spectroscopy with Scattered Light Correction.

Raman spectroscopy is capable of determining the composition of mixtures quantitatively and qualitatively. However, this technology reaches its limits when used to examine liquid dispersed mixtures of substances. In these emulsions, light scattering occurs at the interfaces of the particles and/or droplets, leading to signal losses that make the results impossible to evaluate. Our previous publications have shown, however, that it is possible to quantify the signal losses using a scattered light probe. In an investigation of the water-toluene-acetone emulsion, the acetone concentration could be determined with a root mean squared error of prediction (RMSEP) of up to 1.5 wt%. Based on this method, further analyses are now being carried out to demonstrate that the correction also makes it possible to determine the acetone concentration in each individual liquid phase. First, a ternary diagram is analytically created by establishing stable conditions and separating the phases for individual measurement. In a second step, the samples are measured as a dispersed mixture with the droplets as interfering factors, demonstrating that the same concentration differences can be measured between both phases.