Glycerol as a Cryoprotectant: An Undergraduate Experiment Using Differential Scanning Calorimetry to Study Glycerol-Water Mixtures

Abstract

This study describes a laboratory experiment performed with undergraduate physical chemistry students utilizing differential scanning calorimetry (DSC) to determine a eutectic phase diagram, measure solution glass transition temperatures (Tg), and predict the glass transition temperature (Tg) of water. The DSC techniques employed determine accurate equilibrium freezing temperatures (Tf) of glycerol-water mixtures with glycerol mole fractions (xg) between 0 and 0.201. When xg ≥ 0.300, the slow rate of crystallization of glycerol inhibits crystallization, and solutions exhibit a Tg rather than a Tf. The Tf’s serve to discuss solid-liquid equilibria and estimate eutectic phase diagrams with varying levels of accuracy. The Tg’s serve to estimate the Tg of water (135.3 ± 1.2 K). Together, these behaviors allow for discussion of glycerol’s effectiveness as a cryoprotectant.