A centrifuge method to determine the solid–liquid phase behavior of eutectic mixtures

The centrifuge method is a novel, equilibrium-based, analytical procedure that allows the construction of solid–liquid phase diagrams of binary eutectic mixtures. In this paper, the development, optimization, and successful verification of the centrifuge method are described. Contrary to common dynamic analysis techniques—differential scanning calorimetry and hot-stage microscopy—the studied mixtures are equilibrated at constant temperature. Therefore, the mixtures do not need to be recrystallized from the melt during analysis. This offers a great advantage for mixtures that exhibit strong supercooling behavior rather than direct crystallization. The centrifuge method was verified by reproducing the binary eutectic phase behavior of both the nearly ideal biphenyl–bibenzyl system and the strongly non-ideal deep eutectic solvent (DES) urea–choline chloride, which is prone to supercooling. Hence, the centrifuge method offers an alternative route to common dynamic analysis techniques for the quantification of the liquid range of DESs and other binary eutectic mixtures