A novel phenolphthalein-based fluorescent sensor for Al3+ sensing in drinking water and herbal tea samples

In this study, 3,3-bis(4-hydroxy-3-((E)-((4-hydroxyphenyl)imino)methyl) phenyl)isobenzofuran-1(3H)-one (HMBP) was designed as a turn-on fluorogenic chemosensor to detect Al3+. Studies were performed in C2H5OH-HEPES (v/v, 9/1, pH 7.0) media at lambda(em) = 475 nm. The LOD value was found to be 0.113 mu M. The stoichiometric ratio of HMBP-Al3+ was determined as 1:2 by Job's plot and ESI-MS as well as H-1 NMR titration. The binding constant of chemosensor HMBP with Al3+ from the Benesi-Hildebrand equation was determined to be 1.21 x 10(8) M-1 . The quantum (Phi) yields were obtained as 0.040 and 0.775 for the chemosensor HMBP and HMBP-Al3+ , respectively. The response of the chemosensor HMBP towards Al3+ was attributed to the strategies of blocking the photo-induced electron transfer (PET) and C=N isomerisation mechanisms. Finally, the sensing of the chemosensor HMBP for the determination of Al3+ in real food samples, drinking waters and herbal teas, were employed.

Automated summary

In this study, a turn-on fluorogenic chemosensor HMBP was designed to detect Al3+. The chemosensor showed high sensitivity and binding capacity towards Al3+, with a stoichiometric ratio of 1:2 and a binding constant of 1.21 x 10(8) M-1. The response of the chemosensor to Al3+ was attributed to blocking the PET and C=N isomerisation mechanisms. The sensor was successfully employed for the determination of Al3+ in real food samples, drinking waters, and herbal teas.