Adsorptive stripping voltammetry of trace manganese in the presence of 2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP).

Trace levels of manganese can be determined by voltammetry after controlled adsorptive accumulation of the manganese-2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complex on a hanging mercury drop electrode. Optimal conditions include an ammonia buffer solution (pH 8.8) containing 1 x 10(-5)M 5-Br-PADAP and an accumulation potential of -1.20 V. The technique offers enhanced sensitivity over analogous measurements of the manganese-Eriochrome Black T chelate. The detection limit is 0.2 mug/1 with 1 min accumulation. The new adsorptive approach is characterized with new selectivity dimensions (compared to the Eriochrome Black T scheme), and is not affected by large excess of commonly coexisting calcium and magnesium cations (which severely interfere in the Eriochrome Black T procedure).