Mercury Porosimetry of Pharmaceutical Powders and Granules

Effect of scanning speed and moisture content of the sample on the result of mercury porosimetry analysis of mannitol and microcrystalline cellulose (Emcocel® 50M) powders and granules produced by wet granulation were studied. In high-pressure porosimetry analysis, the smallest pores (diameter <20 nm) of the powders and granules could not be detected accurately when high scanning speeds were used. If the total pore volume is the only parameter of interest, fast scanning speed can be used, because the scanning speed does not affect this value. In high-pressure porosimetry analysis, the volume of the smallest pores (diameter <40 nm) of mannitol and microcrystalline cellulose granules increased with increasing water content. For powders, no effect of moisture on the volume of the smallest pores was observed. Thus, the increase in the volume of the smallest pores of granules with increasing moisture is related to the structure of the granules. Measurement of the water content of the samples together with proper drying of the samples before the porosity measurement is extremely important.