Evaluation of the Loss of Propylene Glycol During Aqueous Film Coating

A Plackett-Burman study was used to determine the coating factors which can affect the loss of propylene glycol, a common water soluble plasticizer used in aqueous film coating, during the film coating process. The processing variables studied were: application rate of the aqueous film coating liquid, atomizing air pressure, drying time, amount of propylene glycol in the aqueous film coating liquid, temperature and the amount of aqueous film coating liquid applied. Analysis of the data shows that the amount of propylene glycol in the film was 81 to 96% less than the theoretical value when considering the amount of the propylene glycol in the aqueous film coating liquid. The loss of propylene glycol was independent of the variables studied. The loss of propylene glycol was also shown to occur in the Accela-Cota during the coating of tablets.