Stock solutions and reagents prepared in the lab expire (Moves away from their perfection) after some time. Most SOPs recommend " the preparation of fresh ones everyday". Please if you have an idea, let me know how long they take. Has anyone ever conducted a perfection in performance trend on them to determine deviation from some standard curve? If used within the day, can results taken at 7am be different from those at 7pm (from the same prepared reagent or stock solution)? how different can they be if the same are used the next 7am (after about 24hrs from prep)?
Thank you Prof Geletii for your reply.
let me give an example of dragendorff solution for alkaloid detection.
I'm thinking it can inform how we can strike a balance between "saving a lab consumables budget "and "not compromising lab results" on the other hand.
Dragendorff"s (potassium iodide-bismuth nitrate) solution is very cheap, Just prepare small volumes and keep them in tightly closed glass flask in the dark.
Dragendorff"s reagent or 2,4-DNP I have been using it for over a year and they work fine. Even at room temp.
Thank you Inamdar for your help. That is great insight to me. I recently happened to work on an alkaloid which couldn't show distinct spots on TLC, the expiry of my dragendorff's was one of my trouble shooting where I had to reluctantly prepare another one.