Exploring the solid-state phases and thermodynamics of calcium l-lactate

Calcium l-lactate, an organic salt derived from l-lactic acid, is used in many fields such as food, pharmaceutical or cosmetic industry. To this date, its solid-state thermodynamics are still poorly understood: a pentahydrate crystalline and anhydrate amorphous forms were already characterized, and potential other hydrates mentioned in literature. For the development of a robust crystallization process or down-line handling of this compound, it is important to know and understand the relationship between the different solid forms to prevent uncontrolled crystallization or solid-solid transformation during storage. In this paper, we aimed at identifying and characterizing novel solid forms of calcium l-lactate. Combining analytical techniques, we confirmed the existence of the pentahydrate and an amorphous anhydrate. In addition, we played on temperature and relative humidity conditions to discover three new crystalline forms (a crystalline anhydrate, monohydrate and dihydrate). This paper is the first occasion where these forms were successfully isolated and characterized.