A NOVEL AND HIGHLY SENSITIVE CATALYTIC METHOD FOR THE DETERMINATION OF ULTRATRACE AMOUNTS OF GOLD IN ORES WITH LINEAR SCAN VOLTAMMETRY AT A DME

Gold(III) has a strong catalytic effect on the slow redox reaction between Ce(IV) and Hg(I) in a sulphuric acid medium at 90-degrees-C, and the Ce(IV) unreacted in the catalytic reaction reacts with benzilic acid to form benzophenone that exhibits a sensitive linear scan voltammetric wave at -0.78 V vs. SCE. This provides the basis for a novel and highly sensitive and selective catalytic method with linear scan voltammetry at a DME for gold. Both reactions of Ce(IV)-Hg(I)-Au(III) and Ce(IV)-benzilic acid are investigated by means of linear scan voltammetry. The detection limit is 0.05 ng/ml with a fixed-reaction time of 15 min. A linear calibration graph from 0.15 to 5 ng/ml is obtained. Possible influences by co-existing ions are examined. Gold in ore samples is analysed by this catalytic method with satisfactory results.