Ice induction in DSC experiments with Snomax®
Résumé
For differential scanning calorimetry (DSC) analysis, controlling the degree of supercooling at which crystallization begins may be required for several studies, experiments, and applications. In this paper, the use of Snomax, an ice nucleating agent (INA), was evaluated to create ice at a desirable temperature range in a DSC aluminum sample pan. The effect of Snomax on the nucleation temperature (Tn) was studied in pure water. Best practices and methods are described in terms of the Tn dependence on three experimental parameters: (i) the Snomax concentration that controls the Tn value for different groups according to the three classes of the Pseudomonas syringae protein aggregates (from which Snomax originates); (ii) the sample volume that affects the presence probabilities of the different INA subpopulations in the solution and that could also favor their deterioration; and (iii) the cooling rate that does not seem to further affect the Tn value. There is no-evidence of time dependence of the nucleation process promoted by Snomax. The presence of artifacts or disturbances introduced by the addition of Snomax into the solution was evaluated. No major disturbances of the thermodynamic characteristics of these solutions were observed with the addition of Snomax below 103 mg L−1 concentration. This underscores the possible use of Snomax for controlling ice nucleation during DSC experiments.