DETERMINATION OF AG(I) WITH CHEMICALLY-MODIFIED CARBON-PASTE ELECTRODE BASED ON 2,3-DICYANO 1,4-NAPHTHOQUINONE

The utility of carbon paste modified with 2,3-dicyano 1,4-naphthoquinone (CYNQ) for the voltammetric determination of Ag(I) is demonstrated. The method is based on the formation of Ag(I) complex with CYNQ by accumulation from the aqueous solution to the electrode surface without an applied potential. Using the medium exchange technique, the electrode was transferred to another media followed by linear-scan voltammetric measurements. The reduction peak of the Ag(I)-CYNQ complex was observed at +0.22 V (vs. SCE). The silver response is studied with respect to paste composition, pH of the measurement solution, reproducibility, interference and other variables. A detection limit of 5 x 10(-8)M was obtained and the calibration curve was linear over the range 1 x 10(-6)-8 x 10(-5)M.