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Development of hot-melt extrusion as a novel technique for the ...

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Finally, <strong>the</strong> XPS analysis confirmed <strong>the</strong> molecular modelling predictions and verified<strong>the</strong> presence <strong>of</strong> H – bonding between <strong>the</strong> drug – polymer functional groups facilitated byHME processing.3.5.3 Nuclear magnetic resonance (NMR) studies1 H NMR spectroscopy can be used to monitor changes in molecular chemicalenvironments by studying <strong>the</strong> movement <strong>of</strong> NMR signals (chemical shift) such <strong>as</strong> <strong>the</strong>changes in <strong>the</strong> 1 H NMR spectra <strong>of</strong> drug and drug/polymer solutions. Chemical shift ()locations <strong>of</strong> drug and polymer 1 H signals were identified and values were calculated aftercomparison with <strong>the</strong> spectra from <strong>the</strong> drug/polymer <strong>for</strong>mulations.Fig. 6.6a: Molecular structure <strong>of</strong> PRP and DPD (NMR peak <strong>as</strong>signment).Table 6.3 presents 1 H NMR chemical shift data and <strong>as</strong>signments <strong>for</strong> PRP, DPD, L100and L100-55 (data not shown). Assignments have been annotated with respect to <strong>the</strong>molecular structures <strong>of</strong> both drugs presented in Fig. 6.6a. It should be noted, that <strong>the</strong> broad 1 HNMR signals from <strong>the</strong> L100 sample have been tentatively <strong>as</strong>signed with respect to <strong>the</strong>polymeric repeat unit. There are a number <strong>of</strong> well resolved multiplets that are also observedin <strong>the</strong> 1 H NMR spectrum <strong>of</strong> <strong>the</strong> commercial polymer, Eudragit L100, but <strong>the</strong> origin <strong>of</strong> <strong>the</strong>sesignals cannot be obtained. The 1 H NMR spectra <strong>for</strong> drug/polymer complexes follow verysimilar <strong>as</strong>signments <strong>as</strong> seen <strong>for</strong> <strong>the</strong> individual molecules (Table 6.3). For example, peakbroadened, PRP, aromatic signals can be observed at 8.28 ppm (H2), 7.81 ppm (H5), 7.39ppm (H8) and 6.95 ppm (H9), in <strong>the</strong> PRP/L100 complex.121 | P a g e

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