New membrane sensors for lead (II) ions are described based on the use of a newly synthesized pyridine carboximide derivatives as neutral ionophore in plasticized PVC membranes (sensor 1) and PbS nanoparticles (NPs) capped in polyvinyl alcohol (PVA) (sensor 2). The sensors exhibited significantly enhanced response towards lead (II) ions over the concentration range 1.0x10-7-1.0x10-3 mol L-1 at pH 3.0 -/6.5 with a lower detection limit of 7.0-10.0 ng mL-1. The sensors displayed near-Nernstian

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... pe of 28.2-33.5 mV per decade for Pb(II) ions. The sensors showed long life span, good selectivity for Pb(II) over a wide variety of other metal ions, long term stability, high reproducibility, and fast response. Validation of the method by measuring the lower detection limit, range, accuracy, precision, repeatability and between-day-variability reveals good performance characteristics of the proposed sensors. Membrane incorporating the neutral ionophore in a flow detector is used in a two channels flow injection set up for continuous monitoring of Pb2+ at a frequency of ca. 48-50 samples h-1. Direct determination of lead in water samples as well as in biological fluids gives results in good agreement with data obtained using standard AAS method.