Monitoring powder blending in pharmaceutical processes by use of near infrared spectroscopy

Obtaining completely uniform distribution of the active principle and excipients in a pharmaceutical preparation is essential with a view to ensuring correct dosage. Uniformity in pharmaceutical formulations has usually been controlled by collecting samples at different stages of the process in order to determine the active principle using a chromatographic or UV-Visible spectroscopic method. In this work, near infrared reflectance spectroscopy (NIRS) was used to monitor blending in order to ensure uniformity in a mixture consisting of three typical pharmaceutical excipients and one active principle. To this end, a method for calculating the Mean Square of Differences between two consecutive spectra was developed with a view to expeditiously identifying the time mixture homogeneity was attained. The performance of the proposed method was compared with that of two others routinely employed to monitor blending by use of the NIRS technique and the results were found to be quite consistent. (C) 2002 Elsevier Science B.V. All rights reserved.