Lead(II)-selective electrodes based on tetrakis(2-hydroxy-1-naphthyl)porphyrins: the effect of atropisomers

PVC membrane electrodes for lead ion based on meso-tetrakis(2-hydroxy-1-naphthyl)porphyrin (THNP:I) and meso-tetrakis(2-methoxy-1-naphthyl)porphyrin (TMNP: II) atropisomers as membrane carriers were prepared. Among their atropisomers, a membrane electrode (m-3) containing (alpha,alpha,alpha,alpha)-THNP (ID) as an ionophore and 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer displays a good Nernstian response (29.2 +/- 0.3 mV/decade) to Pb2+ in Pb(NO3)(2) solutions over the linear range of 3.2 x 10(-5) to 1 x 10(-1) M at room temperature. The limit of detection was 3.5 x 10(-6) M. It has a fast response time within 10 s over the entire concentration range and the potentials remain constant for more than 5 min and can be used for at least 3 months without any divergence in potentials. The proposed electrode revealed good selectivity and response for Pb2+ over a wide variety of other metal ions in a pH 6.0 buffer solutions and good reproducibility of base line in subsequent measurements. (C) 2003 Elsevier B.V. All rights reserved.