The Solid–Liquid Equilibrium and Crystal Habit of l‑Carnitine Fumarate

The solid–liquid equilibrium data of l-carnitine fumarate in methanol + (ethanol/1-propanol/2-propanol) binary mixed systems were determined at temperatures ranging from 288.15 to 328.15 K, while the solubility data of l-carnitine fumarate in (methanol +1-butanol) mixtures were determined from T = (293.15 to 333.15) K because of its low solubility in low temperature. All experimental data were obtained by the gravimetric method under atmospheric pressure. At each composition point, the data increases with the increasing temperature in all determined solutions. A similar trend is also observed when the mole fraction of methanol increases in all binary solvent mixtures for each temperature. It is also found that the solubility data of l-carnitine fumarate in these binary mixtures rank as (methanol + ethanol) > (methanol +1-propanol) > (methanol +2-propanol) > (methanol +1-butanol). The modified Apelblat equation, (CNIBS)/Redlich–Kister model, Solubility–Polarity model, and Jouyban–Acree model were employed to correlate the solubility data determined, and all of them show good agreement with experimental value. Furthermore, the crystal morphology and size distribution of l-carnitine fumarate in different solvents was studied in order to select favorable solvents for good crystal habits.