I'm doing in-vitro drug release study using dialysis bag method and collecting samples from the external medium at several time points, subjecting to UV-Vis spectrophotometry. But my absorbance data is increasing for the first two time points and starts to drop constantly from the third time point till the end. This means the concentration of drug released becomes lesser and lesser as time passes. Is it normal to have this kind of trend? If yes, then how could I convert my data into constantly increasing cumulative drug release percentage?
Dear Wei Wei, it is very normal, since the displacement gradient is based on the concentration difference to equilibrate the medium. For the cumulative drug released, please have a look at the following RG threads and the attached docs. My Regards
https://www.researchgate.net/post/How-to-find-cumulative-drug-released-amount-and-percentage#:~:text=For cumulative drug release%2C dilution,(%400min%2B 5min%2B10min).
https://www.researchgate.net/post/How_do_I_calculate_cumulative_drug_release
Dear Wei Wei, if the value of absorbance is decreasing after 2nd reading, it clearly indicates without any doubt that the released drug has now begun to degrade in the release media. That is why, the absorbance values are declining. I will suggest you to first go through the conditions like temperature, pH, nature of solvent, presence of light, etc. at which the drug you are working on remains stable, only then accordingly design your experiment of release. This will definitely help you in getting good results.
Best wishes
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