Colorimetric sensing of H2PO4− using a Pb2+ complex of a pyridylazo dye in aqueous solution

Abstract

AbstractThis study develops a sensitive and selective colorimetric probe for the detection of dihydrogen phosphate (H2PO4−) based on a lead ion (Pb2+) complex of a commercially available pyridylazo dye (PAPS) in aqueous media under physiological conditions. The complex was made by adding Pb2+ to PAPS in a 1:1 stoichiometric ratio (PAPS‐Pb2+), which was accompanied by the remarkable solution change from yellow to purple. The colorimetric sensing of H2PO4− over other anions with PAPS‐Pb2+ occurred owing to the regeneration of original PAPS by the interaction of H2PO4− with Pb2+ in a 1:2 molar ratio. Moreover, the H2PO4− detection was less affected by the presence of other coexisting competitive anions. The colorimetric naked‐eye behaviour of PAPS‐Pb2+ rendered a useful and convenient probe for the detection of H2PO4− via the indicator displacement assay.