Instrumental color measurement: a method for judging the appearance of tablets

An instrumental method for the quantification of the color and the discoloration of tablets is presented. The results are not influenced by external factors and are more rapidly accessible compared with visual determination. Two of the measured parameters, lightness (delta L*) and yellowishness (delta b*) were found to reflect the changes in coloration observed in stability tests on white metoprolol tablets. Correlation studies between visual judgments and instrumental measurements are presented. The instrumental performance was carefully examined, and the results indicate that the employed instrument gives color parameters in the same range for tablet samples irrespective of whether the examined tablet surface has an engraving on it or not.