ASSESSMENT OF THICKNESS VARIATION AND SURFACE-ROUGHNESS OF AQUEOUS FILM-COATED TABLETS USING A LIGHT-SECTION MICROSCOPE

The Light-Section Microscope measures the thickness and surface roughn ess of transparent film coats without contacting them. It enables the determination of tablet film coat thickness at different regions on a tablet surface and analysis of coat thickness variation. Examination o f aqueous film coated tablets using a Light-Section Microscope has sho wn that the coat application conditions can influence the film density and thickness, film thickness variation and film coat surface roughne ss. Coat application conditions which give rise to smoother surfaces a re shown to produce more dense, thinner coats which may exhibit a more even thickness on smooth substrates but larger variations in film thi ckness on rough substrates. The potential for film thickness and surfa ce roughness to vary at different positions on the substrate surface h as also been demonstrated, with film coats tending to be smoother and thinner at the periphery of tablet faces.