SELECTIVE CD2-MEMBRANE ELECTRODE, EMIS-C D .2. ELECTRODE SELECTIVITY AND RESPONSE TO COMPLEXING AGENTS()

The EMIS-Cd coefficients of selectivity to some metallic cations and h alides, as well as its response to Cd2+ complexing agents are presente d. The selectivity coefficients were determined by the mixed solution (i.e. primary and interferent ions) method, the results being used gra phically or in calculations. The electrode shows a good selectivity to the Zn2+, Ni2+, Co2+ cations (p(K)Cd,N values ranging 1.49 - 3.48), w hile the Ag+, Hg2+, Hg-2(2+), Cu2+ and Pb2+ are strong interferents. A mong the halides, the weakest interferent is I-(p(K)Cd,I = 3.75), whil e the Cl- and Br- are a little stronger than I- (p(K)Cd,Cl = 2.30; p(K )Cd,Br = 2.25). As compared to the NTA and EDTA complexing agents, the electrode presents a linear response but a Subnernstian and pH depend ent one.