Recently a tagging reagent with superior qualities for LC analysis was developed for the derivatization of primary amines which yield adducts that are highly fluorescent. This reagent, naphthalenedialdehyde (NDA), reacts with primary amines in the presence of cyanide ion to yield highly fluorescent cyano-benz[f]-isoindole (CBI) products. High yields of isoindoles are formed in a relatively short period of time when the reaction is carried out at pH = 9.5. These isoindoles have also been shown to be stable for extended periods of time after the derivatization reaction has been initiated. Thus, the NDA/CN reagent is very useful for the trace analysis of primary amines. Indeed, attomole amounts of amino acids have been analyzed by HPLC with the NDA/CN reaction, with the use of laser-induced fluorescence detection. Another attractive feature of the NDA/CN derivatization scheme is that the excitation and emission fluorescence maxima are independent of the type of primary amine and the solvent. In addition, the long-term stability of CBI-amines permits pre-column derivatization for HPLC analysis rather than post-column derivatization when ortho-phthaldehyde (OPA) is used as the reagent.

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