Water sorption and near IR spectroscopy to study the differences between microcrystalline cellulose and silicified microcrystalline cellulose before and after wet granulation

Silicified microcrystalline cellulose (SMCC) has been shown to have advantages over conventional microcrystalline cellulose (MCC). These advantages are (i) improved tablet strength compared to that achieved with MCC, (ii) the retention of compressibility after wet granulation, whereas MCC produces weaker tablets after wet granulation, and (iii) superior flow properties than MCC. In this study gravimetric and calorimetric vapour sorption data and near IR spectroscopy have been used to study MCC and SMCC before and after wet granulation. It was found that MCC, SMCC and wet granulated SMCC had essentially identical physical structures (except for a size increase due to granulation). Wet granulated MCC had a different enthalpy of water sorption at low RH, and its near IR spectrum was different from the other samples in the region which relates to C-H bonding. It can be concluded that MCC and SMCC are of very similar structures, thus these analytical techniques cannot provide an explanation for the improvements in compressibility. However the change in compressibility in MCC after wet granulation may relate to the observed differences in internal bonding in this sample. (C) 1999 Elsevier Science B.V. All rights reserved.