No abstract

The lipophillic ammonium salt of 1-pyrrolidine dicarbodithioic acid (PCDT) (I) was introduced as a new selective ionophore for an iron selective electrode. In addition, the effect of immobilization of 18-crown-6 (18CE6) (membrane type-II), on the electrode performance was discussed. The slope of the PCDT-based (I) electrode was (20 mV/decade). The linear concentration range was (10 À5 -10 À1 M) after one day doping. The detection limit for electrode type-(II) was (1.3 Â 10 À6 M). For membrane with only 18CE6 (type-III) the linear range and the detection limit were improved (10 À5 -10 À1 M and 3.2 Â 10 À6 M, respectively). The pH-range was between 5 -11 for type-II, and III electrodes, while it was 7 -11 for type-I electrode. 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 Ag þ and Pb 2þ were the real interference for type-III electrode. Application of using the electrode for the determination of iron in lubrication oil samples was performed with RSD (1.77 -2.7%) and (1.01 -2.3%) for type-II and III electrodes, respectively. The corresponding recovery ranges were (93.0 -99.9%) and (96.3 -100%). The obtained results were compared to those of an atomic absorption spectrophotometric method.