Tetrabenzyl pyrophosphate as a new class of neutral carrier responsive to lead ion

Tetrabenzyl pyrophosphate and diphenylphosphinic anhydride, with two phosph oryl groups (P=O) as ligating sites, can be used as novel ionophores to mak e Pb2+-selective membrane electrodes. A good result was obtained with tetra benzyl pyrophosphate, and the electrode based on this ionophore and bis(1-b utylpentyl) adipate as a solvent mediator in a poly(vinyl chloride) membran e matrix exhibited a near-Nernstian response to Pb2+ in the concentration r ange of 1 x 10(-5)-1 x 10(-2) M with a slope of 28.7 mV per concentration d ecade in a solution containing 0.1 M Mg(NO3)(2). The limit of detection was 3 x 10(-6) M. The selectivity of this electrode to other metal cations was comparable to the best case in many Pb2+-selective electrodes so far devel oped. Addition of potassium tetrakis(p-chlorophenyl)borate (40 mol% relativ e to tetrabenzyl pyrophosphate) caused at drastic change in the response sl ope (53.3 mV per concentration decade), probably due to the formation of Pb A(+), where A stands for anions present in the sample solution, and decreas ed significantly the electrode selectivity to other metal cations. (C) 2000 Elsevier Science B.V. All rights reserved.