Ics. Fraga et al., Determination of molybdenum in the presence of 2-(2-benzothiazolylazo)-p-cresol by catalytic-adsorptive stripping voltammetry, FRESEN J AN, 366(3), 2000, pp. 307-309
The adsorptive collection of the molybdenum (VI) complexed with 2-(2-benzot
hiazolylazo)-p-cresol (BTAC) coupled with the catalytic current of the adso
rbed complex at a static mercury drop electrode yields an ultrasensitive vo
ltammetric procedure for the determination of molybdenum. Optimal experimen
tal conditions were: a stirred acetate buffer 0.2 M (pH 3.5) as supporting
electrolyte, a BTAC concentration of 1.0 x 10(-6) M as ligand, and a concen
tration of 0.1 M potassium nitrate as the oxidizing agent. In addition, a p
reconcentration potential of -0.080 V vs Ag/AgCl (3 M KCl), equi libration
time of 15 s, a frequency of 30 Hz, a scan increment of 2 mV, a pulse ampli
tude of 0.050 mV, and a drop area of 0.032 cm(2) were used. The cyclic volt
ammogram was recorded using a staircase wave with a scan rate of 100 mV/s.
The forward scan starts at the initial potential of -0.080 V and is reverse
d at -0.90 V. Using the catalytic current at similar to -0.55 V the respons
e to the Mo(VI) was found to be linear over a concentration range of 1.0-10
.0 mu g/L. The limit of detection is as low as 6.2 x 10(-10) M with 4 min o
f preconcentration time. The possible interference of other trace ions was
investigated. The merits of this procedure are demonstrated using of refere
nce samples.