Crystallisation of alpha-lactose monohydrate from dimethyl sulfoxide (DMSO) solutions: influence of beta-lactose

In this study, the dimethyl sulfoxide (DMSO)-lactose system has been used t o study the effect of beta-lactose on the morphology of alpha-lactose monoh ydrate crystals. DMSO was used as the solvent as it greatly reduces the rat e of mutarotation of alpha-lactose to beta-lactose. It is shown that as the beta-content of the solution increases, the crystal shape starts increasin g in the a and b directions, whereas the major growth occurs in the c direc tion at low levels of beta-lactose. The morphology of the alpha-lactose mon ohydrate crystal calculated by molecular modelling is in good agreement wit h that of the crystals grown in the presence of low beta-lactose concentrat ions. Atomic force microscopy has revealed growth spirals and unit cell hig h steps on the (0 2 0) face of crystals grown in the presence of low beta-a nomer concentration. (C) 1999 Elsevier Science B.V. All rights reserved.