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

[Display omitted] •A novel phenolphthalein-based fluorogenic ''turn-on'' sensor for Al3+ was developed.•The sensing platform demonstrated a high selectivity and sensitivity.•Chemo-sensor HMBP has low detection limit (0.113 µM).•Studies in real samples showed its value in practical food applications. 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 λem = 475 nm. The LOD value was found to be 0.113 µM. The stoichiometric ratio of HMBP-Al3+ was determined as 1:2 by Job's plot and ESI-MS as well as 1H NMR titration. The binding constant of chemosensor HMBP with Al3+ from the Benesi-Hildebrand equation was determined to be 1.21 × 108 M−1. The quantum (Φ) 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 CN 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.