Immediate detection of Co2+ by a phthalazine‐based colorimetric chemosensor

Abstract We designed a colorimetric chemosensor based on phthalazine ((E)‐9‐((2‐(phthalazin‐1‐yl)hydrazono)methyl)‐2,3,6,7‐tetrahydro‐1H,5H‐pyrido[3,2,1‐ij]quinoline‐8‐ol), denoted HPJ , for detecting Co 2+ . In the presence of Co 2+ , HPJ undergoes a colour variation from yellow to dark pink. Analysis of a Job plot and electrospray ionisation‐mass spectra enabled the binding mode of HPJ to Co 2+ to be determined as a 1:1 ratio. The detection limit of Co 2+ with HPJ was 1.74 μM. In addition, the feasibility of using HPJ in the form of a test strip was confirmed. The sensing process of Co 2+ by HPJ was monitored by using a Job plot, proton nuclear magnetic resonance titration, electrospray ionisation‐mass spectrometry and ultraviolet‐visible titration.