Evaluation of Magnesium Stearate Distribution on Tablets Prepared by an External Lubrication System Using Energy-dispersion X-ray Analysis

Upon the adoption of an external lubrication system (ELS) for tableting, control of the content uniformity of lubricant among tablets and its distribution on the tablet surface becomes extremely important. An energy-dispersion X-ray analyzer (EDX) attached to a scanning electron microscope was used to assess these parameters. The content of magnesium stearate (Mg-St) on the tablet surface significantly increased upon the application of the charged voltage of ELS on the upper punch side, die side, and lower punch side of tablet. However, there was no significant difference between the various charged voltages. Further, Mg-St concentration decreased with an increase in tableting rate and was almost the same at the center, edge, and middle of the tablet surface. A relatively large deviation of the data suggested the localization of Mg-St on the tablet surface. A clear correlation was observed between tablet disintegration time and Mg-St concentration. These findings may help empirical understanding of the role of Mg-St in the tableting process.