Investigation of porosity of tablets using photoacoustic spectroscopy (PAS)

Tablet porosity strongly affects pharmaceutical and biopharmaceutical properties of the tablet. The present aim was to develop a novel non-destructive porosity measurement technique for tablets using photoacoustic spectroscopy (PAS) method. The porosity of starch acetate flat-faced tablets was calculated from the true density, determined by helium pycnometry, and tablet density, based on tablet dimensions and weight. The sample set comprised of 18 tablets whose porosity varied from 14 to 40%. The photoacoustic spectra were measured using a FT-IR spectrometer equipped with a PAS accessory. The step-scan mode with 100 Hz modulation frequency and a wide wavenumber range was used. The resulting amplitude and phase spectra show clear trends with respect to the tablet porosity. The relative porosity prediction error for one tablet, using the 17 others as the calibration set, was of order 1%. In conclusion, the results demonstrate that PAS is a potential method for tablet porosity measurements.