Am. Twitchell et al., ASSESSMENT OF THICKNESS VARIATION AND SURFACE-ROUGHNESS OF AQUEOUS FILM-COATED TABLETS USING A LIGHT-SECTION MICROSCOPE, Drug development and industrial pharmacy, 21(14), 1995, pp. 1611-1619
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.