Determination of the rate of gravitational flow through a hopper aperture is one of the most widely used methods for the evaluation of flowability properties of pharmaceutical materials. This work studies the influence of the diameter of a conical hopper aperture in the range of 0.6-1.5 cm on the mass flow rate Q (g/s) of the pharmaceutical excipient, sorbitol, for direct compression (Merisorb 200, MS 200) and its size fractions in the range of 0.080-0.400 mm in order to recommend the appropriate aperture size for testing. Non-linear dependence of the flow rate on the aperture diameter is modeled by the Jones-Pilpel power equation. Using the actual parameters of the power equation, the precision of the mass flow rate prediction was the basic criterion in optimization of the orifice diameter. It was detected experimentally that for the evaluation of the flow rate of MS 200 and its size fractions in the range used a 1.0 cm aperture is recommended, which allows the most precise prediction of the flow rate.Key words: particulate material excipient, flow equation conical hopper size fraction.

Flow Equations for Free-Flowable Particle Fractions of Sorbitol for Direct Compression: An Exploratory Multiple Regression Analysis of Particle and Orifice Size Influence