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Oh, Sigma…

I'm a little busy with blog-syn and actual work at the moment, but a friend just sent me this screenshot from the Aldrich website, which I think I'll share with you all (annotation his):



Now, correct me if I'm wrong, but if I wanted to report a compound in, say, J. Med. Chem., I'm quite sure that TLC would not be an acceptable proof of purity. And if anyone knows how I can TLC quantitatively, please leave a comment, because I'm getting sick of running all these crude NMRs and HPLCs...

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  1. (HP)TLC is a quantitative method if done properly. Plates are spotted by a robot to accurately control droplet size and position. A reference standard (with a known assay) is used for calibration. Signals are detected by a plate reader. Overall it is the same procedure as for quantification by HPLC, but reference and samples can be run in parallel.

  2. You can do even fancier things with a TLC plate: check out this Org. Lett. (OL 2008, 10, 3493, with special note to Fig. 2 on page 2:


    As synthetic organic chemist I say: If you can make your PI buying this thing…

  3. Has anyone tried to scrape off a spot from the TLC plate, extract and take a mass? That would be great to do when you have confusing reactions or don’t have time to isolate all the compounds from a reaction.

    • yes i did. can come pretty handy. scratch the spot off, suspend the silica gel in isopropanol, filter through syringe filter, evaporate / redisolve if necessary, inject in LCMS, GCMS or whatever you like. cheers

  4. of course TLC can be quantitative, use tlc scanner.

  5. Nothing from Aldrich could surprise me now since I saw some products are Kosher grade.

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