An optical sensor is described for a sensitive and selective spectro photo metric determination of Pb(II) ions in aqueous solution. A sensor membrane based on 4-hydroxy salophen has been developed for the determination of Pb(II) ions that displays excellent performance. The membrane responds to lead(II) ions, giving a color change from colorless to yellow in a buffer solution (pH 3.1). The optode has a linear range of 1.0 x 10(-3)-1.0 x 10(-7) mol L-1 Pb(II) ions with a detection limit of 8.6 x 10(-8) mol L-1 Pb(II). The response time is within 10 min depending on the concentration of Pb(II) ions such that it can quantitatively detect Pb(II) even at concentration levels of 8.6 x 10(-1) mol L-1 Pb(II) (0.018 ppm). The optode developed here is found to be stable, cost effective. easy to prepare, and efficient for direct determination of Pb(II) in a variety of aqueous samples using spectrophotometry. However, it is for one time use only as the reaction of Pb(II) with 4-hydroxy salophen is irreversible. The optode was successfully used for measuring Pb(II) ions in different water samples and in SRM sample. (C) 2009 Elsevier B.V. All rights reserved.