CRYSTALLISATION OF α-LACTOSE MONOHYDRATE FROM AQUEOUS SOLUTION

摘要

The crystallisation of α-lactose monohydrate (αLM) by primary nucleation is a difficult procedure due to exceedingly long induction times needed to develop crystallisation under often quite high supersaturations. Even when the nucleation is induced, growth proceeds extremely slowly resulting in dead times of as long as several hours before measurable growth initiates. The development of crystallisation is therefore usually carried out by seeding which places some restrictions on the control of the process. We have re-examined the process of primary nucleation of this material. As a result we believe that all of these peculiarities can be attributed to the previously wellknown development in solution of the isomer, β-lactose, which then acts as a nucleation and growth inhibitor. The influence of β-lactose on both growth and morphology has been examined. The sectoral incorporation of β-lactose into the growing αLM crystal has been defined and shown to be consistent with the development of the asymmetric tomahawk morphology which the crystal shows. Methods have been developed for producing a-lactose monohydrate by primary nucleation, which yield crystals of more regular habit and which contain lower quantities of the β-lactose.