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.