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Abstract
A chemically modified carbon paste electrode was developed for the determination of silver by incorporating the ion-exchanger Dowex 50 W × 12 into a conventional graphite-Nujol oil paste. Silver(I) was accumulated at the electrode surface from solutions of the sample under open circuit conditions, then reduced at constant potential in a separate 0.1 M HNO3 solution and finally determined by square wave (Osteryoung) anodic stripping voltammetry. The influence of paste composition, acummulation/reduction time, possible interferences and other experimental variables on the height and shape of the anodic peak was examined in detail. For 5 min of accumulation, the linear range was from 1.62 µg L−1 to 0.8 mg L−1 with a detection limit of 0.27 µg L−1. The dynamic range could be extended up to 2.5 mg L−1 (from 0.92 µg L−1 to 2.5 mg L−1) with 20 min of preconcentration. The method showed good tolerance for Cu2+, Fe3+, Cd2+, Zn2+, Pb2+, and Au3+. Interference from Hg2+ up to 5 mg L−1 was avoided by masking with EDTA in the preconcentration step.
Acknowledgment
The financial support of the Secretaría de Ciencia y Técnica (Project Nr. 9001) of the Universidad Nacional de San Luis, Argentina, is gratefully acknowledged.
