Azo compounds as reagents for the voltammetric determination of molybdenum(VI)

Linear sweep voltammograms of Lumogallion IREA (pH 2), Magneson IREA (pH 2) , 4-(2-pyridylazo)resorcinol (pH 4.8), and 2-(5-bromo-2-pyridylazo)-5-dieth ylaminophenol (pH 4.8) in the presence of molybdenum(VI) exhibit peaks at p otentials more negative than the potentials of reduction peaks of the reage nts by approximately 0.1 V. In all of the above cases, the heights of these peaks linearly increased with an increase in the concentration of molybden um(VI) in the range from 5 x 10(-7) to 2.5 x 10(-6) M; thus, these peaks ca n be used for the determination of molybdenum. The simultaneous proportiona l decrease in the heights of the cathodic peaks of the reagents can be used for indirect determination of molybdenum(VI). The limits of detection with out preliminary accumulation at a dropping mercury electrode with a drop ti me of 5 s are (1.5-3.9) x 10(-7) M, depending on the nature of the reagent and the technique used for determining the concentration.