Quantitation of the active compound and major excipients in a pharmaceutical formulation by near infrared diffuse reflectance spectroscopy with fibre optical probe

A new method for analyses of a commercial pharmaceutical formulation based on near infrared diffuse reflectance spectroscopy (NIRRS) with fibre optical probe and using partial least-squares regression (PLS) for multivariate calibration is proposed. Analyses include the determination of the active compound and major excipients. The influence of the spectral mode and wavelength range used are studied. Satisfactory predictive results for production samples require calibration with laboratory-made samples covering the concentration range involved in the manufacturing process, as well as samples from various production batches, which introduce the variation sources inherent in such a process. The number of production samples to be used for calibration in order to ensure correct prediction of new production samples is discussed.