The application of in situ focused beam reflectance measurement (FBRM) and particle vision measurement (PVM) in monitoring transformation of glycine polymorphs is introduced. The effect of solvent composition and temperature on the transformation from β- to α-glycine was investigated. It is noted that the transformation kinetics are highly sensitive to both the solvent composition and temperature and the transformation rate is a function of ethanol content in aqueous ethanol mixtures. At 303 K, high initial ethanol concentration accounts for a steady transformation. At the same ethanol content, the transformation rate decreases with decrease in temperature. A smoother transformation was observed at 293 K. The results are consistent with the solvent-mediated transformation mechanism in which β-glycine dissolves and α-glycine nucleates and grows. The thermodynamically stable γ-glycine was not observed. Understanding these effects can aid optimization and improve process control.
- solvent composition
- focused beam reflectance measurement
- aqueous ethanol mixtures