INVESTIGATION OF HYDROGEL FORMATION FROM HYDROXYPROPYLMETHYLCELLULOSE(HPMC) BY NMR-SPECTROSCOPY AND NMR IMAGING TECHNIQUES

NMR imaging has been used to investigate the in situ swelling behavior of 2-hydroxypropylmethylcellulose (HPMC) tablets in a sample geometry chosen for the simplicity of its diffusion behavior. Preliminary H-1 NMR spectroscopy experiments were performed on equilibrated mixtures o f HPMC and water. From these, the dependence of the H-1 T-1 and T-2 re laxation parameters of the water protons with respect to HPMC weight p ercent were obtained. Further analysis of the T-2 values and H-1 z-spe ctroscopic data revealed that as the polymer concentration was increas ed from 10% to 20% w/w HPMC, the polymer mobility decreased substantia lly. One-dimensional NMR imaging of H-1 in the swelling tablet system was used to monitor the movement of water into the polymer and to calc ulate the T-2 parameters across the system. HPMC weight percents were calculated from these T-2 values using the previously determined calib ration. HPMC distributions were determined for two tablet thicknesses. Similar swelling behavior was observed for both thicknesses at early times prior to the thinner tablet becoming completely hydrated.