New nickel(II) selective potentiometric sensor based on 5,7,12,14-tetramethyldibenzotetraazaannulene in a poly(vinyl chloride) matrix

5,7,12,14-Tetramethyldibenzotctraazaannulene (Me(4)Bzo(2)TAA) has been explored as an electroactive material for preparing poly(vinyl chloride) (PVC)-based membrane electrodes selective to Ni2+. The membrane having the constituents Me(4)Bzo(2)TAA, sodium tetraphenyl borate (NaTPB) and PVC in the optimum ratio 2:1:97 (w/w) gave the best working concentration range (7.9x 10(-6)-1.0x 10(-1) M) with a Nernstian slope (30.0+-1.0 mV/decade of activity) in the pH range 2.7-7.6. The sensor exhibits a fast response time of 15 s. The electrode shows good selectivity for nickel(II) over a number of mono-, bi- and tri-valent cations. Analytical application of the electrode has been investigated for the quantitative determination of Ni2+ in chocolates and the sensor has been successfully used as an indicator electrode in the potentiometric titration of Ni2+ against EDTA. (C) 2000 Elsevier Science B.V. All rights reserved.