Effect of presence of 18-crown-6 on the response of 1-pyrrolidine dicarbodithioate-based lead selective electrode.

The lipophilic ammonium salt of 1-pyrrolidine dicarbodithioic acid (PCDT)[I] was introduced as a selective ionophore for a sensitive Pb-ion selective electrode. Also, the effect of immobilization of 18-crown-6 (CW), into the above membrane, on the electrode performance was discussed. The slope of the PCDT-based [I] electrode was (26-30 mV decade(-1)), while it was (29-30 mV decade(-1)) for (PCDT+CW)-based [II] electrode according to the doping time. The linear concentration ranges were (1x10(-6)-1x10(-1) M) and (5x10(-5)-1x10(-1) M) for electrode types [I] and [II] after one-day doping. The working pH ranges were (5.0-10.0) and (7.0-10.0) for electrode types [I] and [II], respectively. Most of the common cations were tested for the evaluation of the electrode selectivity with correlation to the ionic radii of the tested cations. Among them only Na(+), Ag(+) and Fe(3+) were the real interference. Application of using the electrode for the determination of lead in lubrication oil samples was performed with RSD (0.86-1.03%). The obtained results were compared to those of an atomic absorption spectrophotometric method.