Abstract-Multispectral UV imaging for determination of the tablet coating thickness

• Anna Novikova^a, 
• Jens M. Carstensen^b, 
• J. Axel Zeitler^c, 
• Thomas Rades^d, 
• Claudia S. Leopold^a, , 

• ^a Division of Pharmaceutical Technology, Department of Chemistry, University of Hamburg, Bundesstraße 45, 20146 Hamburg, Germany
• ^b Department of Applied Mathematics and Computer Science, Technical University of Denmark, Richard Petersens Plads Building 321, 2800 Lyngby, Denmark
• ^c Department of Chemical Engineering, University of Cambridge, New Museums Site, Pembroke Street, Cambridge, CB2 3RA, United Kingdom
• ^d Department of Pharmacy, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark

http://www.sciencedirect.com/science/article/pii/S0022354917300886

The applicability of off-line multispectral ultraviolet (UV) imaging in combination with multivariate data analysis was investigated to determine the coating thickness and its distribution on the tablet surface during lab scale coating. The UV imaging results were compared with the weight gain measured for each individual tablet and the corresponding coating thickness and its distribution measured by terahertz pulsed imaging (TPI). Three different tablet formulations were investigated, two of which contained UV active tablet cores. Three coating formulations were applied: Aquacoat^®ECD (a mainly translucent coating) and Eudragit^® NE (a turbid coating containing solid particles). It was shown that UV imaging is a fast and non-destructive method to predict individual tablet weight gain as well as coating thickness. The coating thickness distribution profiles determined by UV imaging correlated to the results of the TPI measurements. UV imaging appears to hold a significant potential as a PAT tool for determination of the tablet coating thickness and its distribution resulting from its high measurement speed, high molar absorptivity and a high scattering coefficient, in addition to relatively low costs.