- Author
- Earl, W. L. | Parrish, F. W.
- Title
- Cross Polarization-Magic Angle Sample Spinning NMR Study of Several Crystal Forms of Lactose.
- Coporate
- National Bureau of Standards, Gaithersburg, MD Dept. of Agriculture, New Orleans, LA
- Journal
- Carbohydrate Research, Vol. 115, No. 1, 23-32, 1983
- Keywords
- acids | cross polarization
- Abstract
- Five different crystalline forms of lactose were investigated using cross polarization-magic angle sample spinning 13C (CP-MAS) NMR. Both the anhydrous beta-lactose and the alpha-lactose monohydrate structures are known from x-ray diffraction studies and the CP-MAS NMR data agree with those structures. The structure of the stable anhydrous alpha-lactose has not been reported. The CP-MAS NMR results indicate that the crystal must have two or more lactose molecules per unit cell. The chemical shifts measured for two mixed crystals with alpha:beta ratios of 5:3 and 4:1 are a direct result of the fact that both materials are real mixed crystals rather than physical mixtures of crystals of pure alpha- and beta-lactose. The chemical shifts also indicate that the lactose molecules in both mixed crystals are in environments similar to the crystalline environment of the stable anhydrous alpha-lactose.