Quantitative analysis of film coating in a pan coater based on in-line sensor measurements

Abstract

A method was developed that enables in-line analysis of film coating thickness on tablets during a pan coating operation. Real-time measurements were made using a diffusereflectance near-infrared (NIR) probe positioned inside the pan during the coating operation. Real-time spectra of replicate batches were used for modeling film growth. Univariate analysis provided a simple method for in-line monitoring of the coating process using NIR data. An empirical geometric 2-vector volumetric growth model was developed, which accounts for differential growth on the face and band regions of biconvex tablets. The thickness of the film coat was determined by monitoring the decrease of absorption bands characteristic of a component of the tablet core and monitoring the increase of bands characteristic of a component in the coating material. There was good correlation between values estimated from the NIR data and the measured tablet volumetric growth. In-line measurements allow the coating process to be stopped when a predetermined tablet coating thickness is achieved.

Terahertz In-Line Sensor for Direct Coating Thickness Measurement of Individual Tablets During Film Coating in Real-Time

“…Nevertheless, process understanding is increasing steadily through advances in the field of modelling film coating on the process scale 3,4 as well as understanding the physicochemical changes of the film formation itself on the micro scale. 5,6 In order to reduce process time and improve the quality of the coating process, a number of optical sensors, for example, at near-infrared frequencies 7,8 or using Raman spectroscopy, 9,10 have been developed previously to monitor the coating operation and to determine the process endpoint. Conceptually, both of these techniques measure the coating thickness indirectly in that they either track the attenuation of the spectral features of one of the constituents, which is exclusive to the tablet core matrix, or the buildup in intensity of the spectral features in a component that is only found in the coating formulation but not in the tablet core.…”

Optimization of Process Parameters for a Quasi-Continuous Tablet Coating System Using Design of Experiments

“…However, due to the limitations of coat thickness estimations using the micrometer screw gauge, the greatest accuracy for coat thickness measurements could be obtained from the central band or edge of the tablet. Coat thickness in these locations were less variable than that at the tablet face and were therefore more suitable for model development in coat thickness prediction (24). Higher variability at tablet face was due to elastic recovery of tablet core materials.…”

Near Infrared Spectroscopy in Drug Discovery and Development Processes

“…In the case of Pérez-Ramos and co-workers who dealt with tablets, the probe was placed directly in the coating pan for diffuse reflectance measurement. A univariate model was used, which followed the decrease and increase of specific bands of a core compound and the coating, respectively [172]. NIR and Raman spectroscopy were used simultaneously during the fluid bed pellet coating process by Dogomolov and co-workers [173].…”