If your analyte has 3X the molecular mass of the reference standard then you should try to weigh about these in a 3:1 ratio, approximately.

This can be roughly judged by their relative molecular masses. You should also aim to weigh roughly equimolar amounts of both analyte and reference material. Recovering the material is not impossible, but would require a separation. You don’t want so little that the mass is uncertain, and not so much that dissolution becomes a concern. This question may be answered for you if you only have a little material, but 10-20 mg would be a sensible amount if you have it. Remember: never return material to the stock bottle! How much should you weigh out? Because I am more of an NMR spectroscopist than an analyst, I would favour the first method, and carefully add the second compound. If you weigh each sample into separate vials then you must be sure that the full contents are quantitatively transferred to the other sample. You can weigh both materials into the same vial, but adjusting the mass of the second compound is then impossible. How you weigh your samples is probably different for everyone. Three replicates would be common if this is necessary. Has one or more signals that do not overlap with a solute signalĭepending on the accuracy you need to achieve, you must decide whether or not you need to do replicates, and how many.The criteria for a suitable internal reference standard have been well documented, and you will need to be satisfied that this compound:

It is a good idea to use a vortex mixer to be certain that the (capped!) vial with a solution of your sample has been thoroughly mixed. You may need to inspect the liquid with good lighting and a magnifying glass to fully convince yourself that the sample satisfies this criterion, and that it has not, e.g., formed a colloid. Try very hard to use a single solvent and it should fully dissolves your sample without heating, adding acid, etc. It is very important to first determine which NMR (deuterated) solvent fully dissolves your compound. Sample preparation Choosing the solvent, and dissolution It is intended solely as a guide to doing this experiment correctly and does not take away your responsibility to show that your procedures are effective, and give the correct result in a robust way. This article is intended to help Mestrelab customers get the best results from “purity” determinations using NMR.

Sample purity mestrenova