Terahertz and Near-Infrared Spectroscopy Quantitative Model for Real Time Film Coating Thickness Process Control (original) (raw)

2014

Abstract

ABSTRACT Critical quality attributes of film coatings, such as coating layer thickness and uniformity, are often determined via indirect measurements. Traditional weight-gain calculations are used to determine the endpoint of coating processes. Such calculations do not offer sufficient information about the coating integrity, which is usually a major concern in pharmaceutical production. Other technologies such as imaging analysis can be used to investigate the film thickness and integrity, however are destructive and require laborious work for samples preparation. The purposes of this work were: (1) to investigate the capability of terahertz spectroscopy to characterize, in a non-destructive manner, the statistical coating thickness distribution of coated multiparticulate dosage forms; (2) to be used as an advanced reference method for developing an in-line NIR quantitative model for the film thickness process control. Non-pareil beads were used as the coating substrates, Eudragit NE 30 D aqueous dispersion was used as the main sustained release coating material. The coating processes were performed in a laboratory scale top-spray fluidized bed processor, important process parameters were carefully controlled to achieve good coating conditions. Near-Infrared spectrometer was used to monitor the coating processes, coated samples were collected at each pre-determined time point. Imaging analysis and terahertz spectroscopy were both used in this work as reference methods. Calibration models were generated for film coating thickness quantification using partial-least squares (PLS) regression. Film coating thickness and uniformity in the useful coating range can be determined by Terahertz spectroscopy. In-line NIR quantitative model can be developed using terahertz spectroscopy as reference method, and the model showed good predicting power with acceptable prediction error. Terahertz spectroscopy can be used for the development of real time monitoring process control tools in coating technologies.

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