Development of a two-dimensional Raman spectroscopy measuring technique for the visualization of mass transfer during droplet formation

• Two-dimensional concentration measurements using Raman spectroscopy. • Non-invasive measurements of mass transfer during droplet formation. • Specially designed optical system to reduce spherical aberrations • Visualization of mass transfer in the system water/acetonitrile/toluene. • Qualitative progression of the droplet concentration over time. A novel two-dimensional Raman spectroscopy measurement setup is developed to visualize mass transfer during droplet formation and applied to the water/acetonitrile/toluene system. This setup enables direct observation of local solute contents. Experiments were conducted using 2 mm and 4 mm droplets with an initial acetonitrile content of 10 wt%. The results are qualitatively consistent with findings reported in the literature for similar systems. Initial calibration measurements using single-phase systems demonstrated linear correlations between measured intensities and solute contents in both phases, though a baseline shift in the organic phase was attributed to the presence of toluene. Applying these correlations to droplet formation experiments resulted in an overestimation of local acetonitrile contents. Future work will focus on further refining the quantification capabilities of the measurement setup.