(742b) Using Optical Coherence Tomography (OCT) to Analyze in Real-Time the Tablet Coating Variability of a Continuous Drum Coating Process

This study demonstrates an in-line measurement system used in a continuous drum coater (Driaconti-T lab, Driam Anlagenbau GmbH). Process monitoring is performed by an optical coherence tomography (OCT) sensor (OCT Pharma 1D, Phyllon GmbH) providing cross-sectional images of film-coatings in a non-destructive and contactless manner.

The continuous coater has three chambers, each with a product volume of around 2 liters of tablets. In continuous operation mode, the tablets are inserted in chamber 1 and transported to chamber 3, while being coated in each of them. Thus, the product is handled in small batches, without exchange of product between the chambers, resulting in a defined residence time for each tablet.

OCT measurement and subsequent automatic data analysis is a method to determine the coating thickness from OCT images without the need of chemometric calibration models, based on a known refractive index of the coating materials. OCT was used to obtain the temporal evolution of the quality parameters, i.e., mean coating thickness, inter-tablet coating variability and intra-tablet coating variability during the coating process. Thereby, the influence of spray rate, air temperature and spray pattern pressure on the quality parameters was studied based on a full-factorial DoE. Additionally, the variability of single drum segments of an extended period of time was studied.

Continuous coating, here in the form of small batches, is an important enabler for continuous manufacturing of solid dosage forms. In combination with an in-line OCT system the coating process can be monitored and actively controlled.