Measurement of lactose crystallinity using Raman spectr...

Measurement of lactose crystallinity using Raman spectroscopy

Measurement of lactose crystallinity using Raman spectroscopy
Bridget M. Murphya, , Stuart W. Prescottb and Ian Larson
22 January 2005
Journal of Pharmaceutical and Biomedical Analysis
Abstract
Raman spectroscopy (RS) was used to determine the crystallinity of lactose (a commonly used carrier in dry powder inhaler (DPI) formulations). Samples of a-lactose monohydrate and amorphous lactose were prepared using ethanol precipitation and lyophilisation respectively. The anomeric forms were confirmed using DSC at a rate of 10 ?C/min and heated to 250 ?C. The Raman spectra of both a-lactose monohydrate and amorphous lactose were obtained. Distinguishable differences were seen between the two spectra including peak areas and intensities. Depolarisation ratios (?) of each form were then determined to identify the crystallinity of the lactose carrier samples. At the prominent Raman bands 865 and 1082 cm-1, significant differences in ? values were observed for crystalline (0.80 ? 0.07, 0.89 ? 0.06 respectively) and amorphous samples (0.44 ? 0.07, 0.51 ? 0.10).