ultratrace determination of cadmium ion in petrochemical sample by a new modified carbon paste electrode as voltammetric sensor

A novel chemically modified carbon paste electrode (cmcpe) impregnated with 4′-(4-chlorophenyl)-2,2′:6′,2′′-terpyridine ligand was prepared and applied for voltammetric determination of cd^2+ ion in petrochemical samples. the effects of ph, ligand amount and supporting electrolyte on the selective adsorption properties for the cd^2+ ion were explored. the sensor displayed substantially good resistance against interfering agents. in the presence of a large excess of na^+, k^+, ca^2+, mg^2+ and pb^2+, the adsorption capacity for cd^2+ was slightly changed, suggesting the high selectivity of cmcpe for cd^2+ions. the parameters controlling the response of the electrode were investigated. the limit of detection (lod) and relative standard deviation (n = 5) were obtained by 3.77 ng/l and 0.45%, respectively. the preconcentration procedure revealed a linear curve within the concentration range of 4 – 3000 ng/l and a good linearity with squared correlation coefficient of (r^2) 0.9988 was achieved. the cv was run starting from –1.5 v to 0.0 v and back (scan rate: 100 mv/s). the best ratio of the cd^2+-ligand in carbon paste was 8% (w/w) for a good detection of c^d2+ ions. optimum ph for maximum adsorption was 4.0 ±0.2. all the instrumental parameters involved in the analytical procedure were optimized. the study was accomplished in britton–robinson (b-r) buffer solution of 2 ng/ml cd^2+ ions. the optimal values of scan rate, pulse amplitude, pulse time, voltage step, voltage step time, deposition potential and deposition time were obtained 100 mv/s, 0.20 v, 0.04 s, 0.005 v, 1.2 s, – 0.95 v and 150 s, respectively.