Detection of amines and unprotected amino acids in aqueous conditions by formation of highly fluorescent iminium ions.

Properly substituted coumarin aldehydes can be used to detect amines and amino acids under neutral, high ionic strength conditions by the formation of highly fluorescent iminium ions. The fluorescence of one sensor increases by 26-fold upon the addition of glycine. This strong florescent response is attributed to hydrogen bonding of the chromophore carbonyl by the acidic iminium proton.