LEAD(II) ION-SELECTIVE ELECTRODES BASED ON CROWN ETHERS

Lead(II) ion-selective poly(vinyl chloride) membrane electrodes based on monobenzo-15-crown-5 (MB15C5), MB15C5-phosphotungstic acid (PW) and MB15C5-phosphomolybdic acid (PMo) as neutral carriers were prepared. All these crown ether electrodes gave linear responses with near-Nernstian slopes of 30 mV per decade within the concentration range 1 x 10(-1)-1 x 10(-5) mol dm-3 Pb2+. The Pb2+ electrodes based on MB15C5-PW and MB15C5-PMo showed better sensitivities, with detection limits of 1 x 10(-6)mol dm-3, than the electrode based on MB15C5 with a detection limit of 1 x 10(-5) mol dm-3. Selectivity coefficients of various interfering ions for these electrodes were determined and were sufficiently small for most of them. Among these electrodes, the electrode based on pure MB15C5 exhibited the best selectivity. Effects of the pH of test solutions, the concentrations of internal solutions in the electrodes and the composition of the membranes were investigated.