Hi, i still have some difficulties in determining drug content of o/w microemulsion.
Currently I have microemulsion for simvastatin with tween 80 and propylene glycol as surfactant/cosurfactant, with oleic acid for the oil.
Previously, I loaded the drug after the microemulsion was formed and proceed to uv vis spectro analysis. But after fursther reading, what i understand for now is that simvastatin should be loaded in the solvent first, which in this case the oleic acid, and followed with mixing it into surfactant and cosurfactant and water. and now i have a question as to how to measure the drug content after drug loading.
-for maximum solubility, should i load excess drugs in all microemulsion components and estimate the solubility from the microemulsion formulation based on simvastatin solubility on each component?
-loading excess amount of simvastatin on each component of microemulsion and followed by forming the microemulsion and followed with spectro/hplc
-or loading excess amount of simvastin to an already formed microemulsion and followed with spectro/hplc
after this, what I understand is that i need to separate the droplets by centrifugation and filtering the supernatant. This filtrate then quantified (in my case uv vis spectro and hplc for comparison). I am using methanol to dilute the filtrate.
from my previous question, it is mentioned that the bonds tween 80 and propylene glycol may intervere with simvastatin absorbance at 230-240 nm. which may bring difficulties in analysis.
so, how to do it actually?
I think the first thing you need to ascertain before estimating drug content is to determine whether or not your drug is physically or chemically encapsulated in your final emulsion. So you can determine whether you are quantifying an active ingredient or a derivative of it?
Thank you Adeyinka Aina , I can confirm that the drug incorporated into the microemulsion by looking for the precipitation that occurs after adding an excess amount and dissolved with an ultrasound bath. after that, I proceed to separate the droplets by centrifugation and supernatant was analyzed with a spectrophotometer and only shows a very small amount of drug compared to how much it was dissolved. it should be around 100-200 mg/ml, but only shows 6 mg/ml. The API has a peak of 238 nm in methanol and the analysis of microemulsion shows a 231 nm peak. I assume in this case, where the drug was in a different solvent, it may show a different peak, or it could be the microemulsion peak that interfere the drug's absorbance.
should i confirm the encapsulation with TEM or similar methods first?
Why not use SEM to study the physical morphology of the micro emulsion with and without the drug first?
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