Use of prediction methods to estimate true density of active pharmaceutical ingredients

High-Precision Absolute (True) Density Measurements on Hygroscopic Powders by Gas Pycnometry: Application to Determining Effects of Formulation and Process on Free Volume of Lyophilized Products

“…Absolute or true density has long been important in characterizing pharmaceutical solids, 8,9 and methodology for precise determination of density has been evaluated and compared. 8,10 The floatation method, involving suspending crystals in a density gradient composed of a material in which the crystal is insoluble, is capable of high precision and does not demand sophisticated equipments, 8 but gas pycnometry, in which volume of a solid impermeable to helium is measured, is also capable of high precision, 11 is convenient in the sense that commercial equipment is readily available, and is likely more suitable for investigation of amorphous powders, although the floatation method has been used with synthetic polymers.…”

Refractive Index Measurement of Pharmaceutical Solids: A Review of Measurement Methods and Pharmaceutical Applications

“…93 However, crystallographic data for new compounds are not routinely available. Therefore, the crystal density is assessed through empirical methods 96 or measured by helium pycnometry. 97 Helium pycnometry measures the pressure difference of helium gas in test cells with and without sample to determine true density.…”

Roller Compaction of Hydrophilic Extended Release Tablets—Combined Effects of Processing Variables and Drug/Matrix Former Particle Size

“…The true densities for ibuprofen powder blends and granules were 1.32 g/cm 3 as calculated from literature (22,24). The measured apparent densities were used to calculate the solid fraction of the powder blends, granules, ribbons and tablets, see Tables VII and VIII.…”

“…Here, ρ app is the apparent density and ρ true is the true density as derived from literature (22)(23)(24). Rat ratio between feeder screw speed and roll speed, Rol roll pressure, HPMC particle size of HPMC, API particle size of API (P paracetamol and I ibuprofen) …”