A sensor of m-cresol polymer film-coated platinum electrode has been fabricated for the detection of lead (II) ions (Pb 2+ ) in aqueous solutions. The study was carried out by the simple potentiometric method by measuring its potentiometric response slope and was confirmed by the cyclic voltammetry technique. The effects of the polymer film thicknesses and the pH of Pb 2+ solution on the response of the sensor were studied. Moreover, the stability, sensitivity, and selectivity of the m-cresol sensor were studied. The best thickness of polymer film was about three cyclic voltammetric runs. This film has Nernstian response slope of 26.5 mV/decade with a detection limit of 1.0 × 10 −7 M at 293 K by the simple potentiometric method. Also, it has a sensitivity of 1.1 × 10 −6 /AM with a detection limit of 7.0 × 10 −7 M by the cyclic voltammetry method. Moreover, the sensor is selective to Pb 2+ ions in the presence of other ions, such as Na + , K + , Mg 2+ , Ca 2+ , Co 2+ , Ni 2+ , and Zn 2+ . Also, the highest response of the sensor to the Pb 2+ ions is achieved over a pH range of 4.0-5.3. The lifetime of the sensor is more than 1 month. The sensor was applied on two natural samples, and the results were compared to the analyses of the atomic absorption spectrophotometer.
K E Y W O R D Sm-cresol, Pb 2+ ions, potentiometric method, sensor
The kinetics of oxidation of [CoI~(EDTA)] 2 (EDTA = ethylenediaminetetraacetate) by N-bromosuccinimide (NBS) in aqueous solution obey the equation:where k2 is the rate constant for the electron-transfer process, K 2 the equilibrium constant for the dissociation of [Con(EDTAH)(H20)] -to [CoJ'(EDTA)(OH)] 3-and K 3 the pre-equilibrium formation constant. The activation parameters are reported. It is proposed that electron transfer proceeds via an inner-sphere mechanism with the formation of an intermediate which slowly generates hexadentate [Com(EDTA)]-.
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