A rapid, naked-eye detection of hypochlorite and bisulfite using a robust and highly-photostable indicator dye Quinaldine Red in aqueous medium

Abstract A “naked-eye” detection of health hazardous bisulfite (HSO 3 − ) and hypochlorite (ClO − ) using an indicator dye (Quinaldine Red, QR) in a wide range of pH is demonstrated. The molecule contains a quinoline moiety linked to an N , N -dimethylaniline moiety with a conjugated double bond. Treatment of QR with HSO 3 − and ClO − , in aqueous solution at near-neutral pH, resulted in a colorless product with high selectivity and sensitivity. The detection limit was 47.8 μM and 0.2 μM for HSO 3 − and ClO − respectively. However, ClO − was 50 times more sensitive and with 2 times faster response compared to HSO 3 − . The detail characterization and related analysis demonstrate the potential of QR for a rapid, robust and highly efficient colorimetric sensor for the practical applications to detect hypochlorite in water samples.