Terahertz Time-Domain Spectroscopy to Identify and Evaluate Anomer in Lactose

Abstract

Lactose powder consisting of α-D-lactose monohydrate and anhydrous β-D-lactose was nondestructively and quantitatively evaluated by transmission-type Terahertz time-domain spectroscopy (THz-TDS). An absorption with peak at 39.7 cm-1 (1.19 THz) was assigned to be derived from anhydrous β-D-lactose, in addition to the absorptions due to α-D-lactose monohydrate with peak at 17.1 cm-1 (0.53 THz) and 45.6 cm-1 (1.37 THz). After deconvolution of the spectra using Lorentzian, integrated intensities of the absorptions with peak at 39.7 cm-1 and 45.6 cm-1 were uniquely dependent on the weight composition ratio of the α-and β-lactose powder. As a result, the net molar-ratio of the α-and β-lactose in lactose powder could be precisely evaluated by the integrated intensity ratio. Further, anomer content in lactose powder extracted from lactose solution was evaluated and the refined and unrefined features were shown by the evaluation method.