A new colorimetric method is presented that allows for simple and effective discrimination between (iso)quinoline nuclei pertinent to many alkaloid species. The method is based on the reversible incorporation of Zn2+ ions into a bis-salphen chromophore under aqueous conditions. The metalation process is a function of the stability of the Zn-N (acceptor-donor) interaction and is accompanied by a clear colorimetric response.
![Colorimetric discrimination between important alkaloid nuclei mediated by a bis-salphen chromophore](https://www.iciq.org/wp-content/uploads/2014/03/Colorimetric-discrimination_eng_noticies_articles_2008_76.gif)