PAT for tableting: Inline monitoring of API and excipients via NIR spectroscopy

• NIR probe mounted on feed frame of tablet press.
• Significant segregation effects toward the process end.
• Calibration transfer with local centering and calculated transfer sample.
• Discussion of Ph. Eur. 2.9.47 with regard to inline measurements.

This paper describes the application and implementation of inline NIR spectroscopy in an industrial tablet press. The content uniformity of a powder was analyzed via a NIR probe mounted on the feed frame. A PLS model with four latent variables (R2 = 0.97, Q2 = 0.95) was developed for the Active Pharmaceutical Ingredient (API) and two main excipients (EX1, EX2), according to the mixture DoE. The RMSEP corresponded to the relative errors of 2.7% for API, 1.7% for EX1 and 2.6% for EX2, compared to the nominal formulation. Transfer of the model, from the lab to an inline setup for manufacturing was achieved using local centering. There was a good agreement between the results of inline NIR and drawn tablets analyzed via UV–Vis. Notably, NIR indicated stochastic segregation behavior of the powder toward the end of the process, which was confirmed by the UV–Vis analysis. The outcome of our work was related to the recently published Ph. Eur. chapter 2.9.47 “Demonstration of uniformity of dosage units using large sample sizes”.

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