Spectrophotometric Determination of Lead(II) Ion by 96-Well Microplate Electrostatically Immobilized Porphyrin

Abstract A water-soluble 5,10,15,20-tetrakis(4-N-methylpyridyl)porphine (TMPyP) was used as a highly sensitive chromogenic reagent for the lead(II) ion. When this TMPyP was complexed with the lead(II) ion, the absorption spectra of TMPyP significantly changed in the Soret band {H2TMPyP: λmax = 423 nm (e: 2.6 × 105 M− cm−1), Pb(II)-tmpyp: λmax =476 nm (e: 1.8 × 105 M−1cm−1)}. In this study, the spectrophotometric multi-determinations of the lead(II) ion were developed using a microplate electrostatically immobilized TMPyP on the surface of the well. As a result, the lead(II) ion was quantitatively reacted within 15 min with TMPyP at pH 9 and 60°C. The determination range of the lead(II) ion was 7.5 × 10−7 M to 1.0 × 10−4 M, the relative standard deviation at median was 4.04% (n = 96), and the detection limit (3σ) was 5.0 × 10−7 M. Also, the same plate was able to be reused ten times. Furthermore, the determination of the lead(II) ion present in tap water was possible with citric acid as a masking agent.