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

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Table 6.3: 1 H NMR <strong>as</strong>signments <strong>for</strong> drugs and polymer (samples were dissolved inCD 3 OD).Propranolol HCl Diphenhydramine HCl Eudragit L100Chemicalshift/ ppmAssignmentChemical shift/ppmAssignmentChemicalshift/ ppmAssignment1.38 H15, 16 2.87 H10, 11 0.80 -1.40 H1, 33.23 – 3.40 H13 a,b 3.38 H9 1.80 – 2.24 H23.49 H14 3.75 H8 3.62 H44.17- 4.26 H11 a,b 5.52 H74.40 H12 7.27 H4, 4‘6.94 H9 7.34 H3, 3‘, 5, 5‘7.38 H8 7.39 H2, 2‘, 6, 6‘7.44 -7.51 H3, 4, 77.81 H58.27 H2In Fig. 6.6b significant changes can be observed <strong>for</strong> <strong>the</strong> peak widths found in <strong>the</strong> 1 H NMRspectra <strong>of</strong> <strong>the</strong> drug and <strong>the</strong> drug/polymer <strong>for</strong>mulations. This can be e<strong>as</strong>ily seen with respect to<strong>the</strong> aromatic 1 H signals found only in <strong>the</strong> drug, resulting in <strong>the</strong> chemical shift locationsbetween 6.5 and 8.5 ppm. The peak width is proportional to transverse relaxation (T 2 ), whicharises <strong>as</strong> <strong>the</strong> result <strong>of</strong> magnetic field differences in <strong>the</strong> sample. As T 2 becomes shorter (f<strong>as</strong>terrelaxation), <strong>the</strong> peak width incre<strong>as</strong>es. The peak broadening <strong>of</strong> <strong>the</strong> 1 H NMR signals after<strong>for</strong>mulation could be attributed to changes in local magnetic fields arising fromintramolecular and intermolecular interactions in <strong>the</strong> sample. Indeed, it h<strong>as</strong> been stated thatchanges in <strong>the</strong> T 2 can be attributed to decre<strong>as</strong>es in rotational freedom <strong>of</strong> small molecules in<strong>the</strong> presence <strong>of</strong> a ‗receptor‘ to which <strong>the</strong>y can interact [30] .122 | P a g e

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