I would like to know if someone knows the correct approach on how to validate the purity of an extracted compound from a pharmaceutical pill. I.e., I want to develop a method to analyse a certain compound (ex. caffeine) but the analytical standard is very expensive. But I have a box of pharmaceutical pills that have that compound in its composition. What I want to know is how do I extract that compound (ex. caffeine) from the pill and can I use it as an analytical standard to my method development? I intend to do a methanolic extraction, do a preparative analysis via HPLC, and a confirmation via analytical HPLC (for compound purity) and MS and NRM for compound identification. Is it possible to do this and is it acceptable for method development and validation?
Thank you for your attention and sorry for this long post.
Of course is possible. You can use an adequate solvent (depending of the polarity of the compound) concentrate and purifiy by recrystallization if you have enought material and prep HPLC. The more important part is how good is your purification method. Analytical HPLC will give you the purity data that you need, and you can repeat the purification until you reach the analytical standard purity. NMR, and MS will garantee the identity, HPLC purity of the compound.
Dear Samir, It’s feasible as stated by Guillermo but there are additional issues. Is the "total" amount of drug in the “box of pharmaceutical pills” enough, taking into account the losses during extraction/purification and the amount needed for the identification/characterization/quantification? You don’t share details on the intended application of the standard and analytic method. My opinion is biased towards drug/medicines analysis/control and applications which must comply with guidelines from both ICH and drug regulatory authorities. You might need to include the quantification of related substances (impurities arising from the synthetic process and also degradation products) which would also require standards for those impurities! There are some additional issues but I don’t want to be pessimistic and discouraging.
When you mention that the "analytical standard is very expensive" are you referring to a CRS (Certified Reference Substance) from USP or EDQM, for instance? They are expensive but are accepted by the drug regulatory authorities (FDA, EMA, WHO) as primary standards. Is the “box of pharmaceutical pills” affordable? If yes it’s because the drug substance is not expensive and you might be able to buy the substance (much, much cheaper) from Sigma-Aldrich (or other company) and perform further purification step(s) without being concerned with the extraction steps. Please note that a “fragile” procedure (even if it is not very important) may lead later on to people questioning the validity of your work, conclusions etc.
The actual procedure for the drug extraction depends on its physicochemical properties as well as the type of “pill” (I’m assuming you’re referring to tablets).
If you need additional info/details you may contact me via RG or lgouveia (at) campus (dot) ul (dot) pt.
Regards, LG
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