Direct chemiluminescent sensing of para-Phenylenediamine over its isomers and analogues via luminol diazotization

Abstract In this work, we report a chemiluminescent (CL) design for the quantitative sensing of para -phenylenediamine (PPD) at sub-μM levels. Experiments determined that PPD accelerates the diazotization of luminol to luminol-diazodium in contrast with its isomers and analogues including o -phenylenediamine, m -phenylenediamine, phenylamine, and m -aminophenol. Based on this finding, a highly selective CL method for sensing trace PPD over its isomers and analogues was first established by measuring the luminol-diazodium yielding enhanced CL. After optimizing all device parameters and experimental variables, a flow sensing manifold with on-line luminol diazotization was investigated. Experiments demonstrated a sensitive CL response to PPD concentrations in the range of 0.30˜3.0μM and 3.0˜10.0μM, with a limit of detection (3σ) of 0.05μM. Our CL sensing method was applied to PPD detection in environmental water samples and hair dyes in good agreement with GC–MS method. The mechanism of PPD-responsive CL was studied and was suggested to involve the conversion of PPD-diazonium to luminol-diazodium, which increases the yield rate of luminol-diazonium, resulting in remarkably enhanced CL.