Some articles show that DSC can not give the details about miscibility of drug and miscibility effect drug release from polymer.
hello , you can determine your drug in many ways depending on the drug itself . eg you can use UV, HPLC but if the drug has absorbency at UV would be easier.
Using SEM you can see if the drug only on the surface or inside your blend
Miscibility itself can be studied by various relaxation methods (DSC, DMA, DEA) - they show whethre the Tg of the polymer shifts under the effect of drug addition. It is not enough, however, as the Tg may shift also if the drug behaves as a filler only. It would be important to know, how much drug is added, what is the polymer matrix etc. Changes in the drug IR spectrum may also gove some information,if they can be seen against the background in the polymer. Release property is a different issue, it does not necessarily correlate with the phase structure.
Imaging techniques like ATR FTIR imaging can be useful if drug and polymer have specific IR bands that can be easily distinguished. Careful sample prep and good contact to ATR are key to get meaningful results. Mapping of polymer and drug can then be done.
Yes, IR microscopy or what we occasionally use for such purposes: confocal Raman microscopy. See http://www.igb.fraunhofer.de/content/dam/igb/de/documents/jahresberichte/Jahresbericht_08.pdf page 64/65, there are some example images.
The key point here is how much the Drug DSC profile (Tg, cristalization or melting) is being affected by the presence of the polymer. If you have only the drug with its DSC profile and the mixture shows exactly the same profile (regarding the drug), it means that the polymer does not affect the drug itself. But sometimes there is a little change in the temperatures of the Drug transitions, so we cant be sure if really there is a incompatibility. The best way to know it is to use isothermal microcalorimetry. better than HPLC in my opinion.
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