DIRECT DETERMINATION OF MOLYBDENUM IN SEAWATER BY ADSORPTION VOLTAMMETRY

Complex ions of molybdenum(VI) with 8-hydroxyquinoline (oxine) are shown to adsorb onto the hanging mercury drop electrode. This property forms the basis of a sensitive electrochemical technique by which dissolved molybdenum in seawater can be determined directly. The reduction current of adsorbed complex ions is measured by differential pulse adsorption voltammetry, preceded by a period of 1 or 2 min of unstirred collection at an adsorption potential of minus 0. 2 V. In the presence of 2 multiplied by 10** minus **3 M oxine and at pH 2. 5 the potential of the main reduction peak is located at minus 0. 59 V. The peak current-molybdenum concentration relationship is linear up to 3 multiplied by 10** minus **7 M; the detection limit is 4 nm.