A Comparison of diffuse Reflectance Ft-Ir Spectroscopy and Dsc in the Characterization of a Drug-Excipient Interaction

Abstract

Differential scanning calorimetry (DSC) and diffuse reflectance Fourier transform infrared spectroscopy (FT-IR) were employed for the characterization of the well-known interaction between aminophylline and lactose. Brown discoloration appears in samples containing 1:5 (w/w) mixtures of aminophylline and lactose following three weeks of storage at 60°C. DSC thermograms can be used to predict that such an interaction will occur, but provide little insight into the nature of the interaction. Using FT-IR, it was possible to show that the discoloration is due to a chemical reaction between ethylenediamine and lactose.