The impact of different nucleation methods with controlled supersaturation on the polymorphism of L-glutamic acid crystals was studied in a 50dm3 semi-batch crystallizer, in which 1.5M H2SO4 was fed into a 1.5M monosodium glutamate solution. Supersaturation was controlled by a feedback loop based on measured ATR-FTIR spectra and on a thermodynamic model developed in house. Ultrasound-initiated nucleation produced pure α-polymorph (over 99.5wt%) in the end product crystals at 1mol/dm3 supersaturation. Seeded crystallization also produced almost pure a-polymorph crystals (over 93wt%), whereas spontaneous nucleation produced a polymorph mixture (from 30-70wt %) under the same operating conditions. This indicates that supersaturation-controlled sonocrystallization can be used to control polymorphism in crystals. The novelty herein is the simplicity of the method directing the generation of a desired polymorph.
- Seed crystals