# How to detect azide group on a primer?

I bought azide-labeled primer for click chemistry, but it didn't work. So I want to prove the existence of azide group. How could I achieve this? I found a method to add PPh3 to Kaiser test reagents, but the concentration of the primer is too low (the protocol needs the solution be higher than 0.1M) and I cannot see the reaction.

• Does click reaction work with labeled nucleotide? – Abel Friedman Dec 4 '14 at 5:21
• No. That's why I would suspect there's problem with azide group :( – leetom Jan 30 '15 at 15:15

One possibility would be to check the IR spectrum. If there's any azide in there the azide band should show up as a strong band at around 2150 cm-1. The trouble is of course that this isn't quantitative, you can only prove the absence of azide, not how much is present.

The Staudinger reaction might be a viable option. PPh3 won't go up in aqueous solution, but sulfonated PPh3 will. One should be able to distinguish starting material and product by 31P NMR. With a known quantity of TPPTS you can even determine % azide in the starting material.