Novel approach to estimate quality of binary random powder mixtures: samples of constant volume. II: Applications of equation to optimize tableting conditions.

In a companion communication, an equation (eq 1) of the homogeneity of binary random mixtures, which applies to constituents differing in particle size and in bulk density, was derived. The present paper demonstrates the practical applications of this equation in optimizing tableting conditions with respect to a high dose uniformity. Tablets of 50:50 (w/w) mixtures of coarse sucrose and of fine microcrystalline cellulose (Avicel PH 101)-talc vehicle were produced on a single-punch machine. Without a spin feeder, the tablets showed variations in content uniformity that were significantly higher than those estimated from eq 1. Correlation analysis between the individual mass and the content of the constituents of the tablets revealed this difference to be due to nonuniformity of the die filling and not due to incomplete mixing. Accordingly, the use of a spin feeder allowed production of tablets with higher dose uniformity, which conformed well with the theoretical optimum predicted with eq 1. Further variation of the processing conditions cannot improve the quality (i.e., varying the tableting speed resulted in equal or in poorer uniformity of dose content).