Determination of molybdenum in the presence of 2-(2-benzothiazolylazo)-p-cresol by catalytic-adsorptive stripping voltammetry.
The adsorptive collection of the molybdenum (VI) complexed with 2-(2-benzothiazolylazo)-p-cresol (BTAC) coupled with the catalytic current of the adsorbed complex at a static mercury drop electrode yields an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental 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 concentration of 0.1 M potassium nitrate as the oxidizing agent. In addition, a preconcentration potential of -0.080 V vs Ag/AgCl (3 M KCl), equilibration time of 15 s, a frequency of 30 Hz, a scan increment of 2 mV, a pulse amplitude of 0.050 mV, and a drop area of 0.032 cm2 were used. The cyclic voltammogram 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 reversed at -0.90 V. Using the catalytic current at approximately -0.55 V the response to the Mo(VI) was found to be linear over a concentration range of 1.0-10.0 microg/L. The limit of detection is as low as 6.2 x 10(-10) M with 4 min of preconcentration time. The possible interference of other trace ions was investigated. The merits of this procedure are demonstrated using of reference samples.
Department of Chemistry, Pontifícia Universidade Católica, Rio de Janeiro, Brazil.
I C
IC
Fraga
P A
PA
Farias
A K
AK
Ohara
D000327:Adsorption; D052160:Benzothiazoles; D002384:Catalysis; D003408:Cresols / Q000032:analysis*; D004563:Electrochemistry / Q000379:methods; D007202:Indicators and Reagents; D008982:Molybdenum / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013844:Thiazoles / Q000032:analysis*; D014131:Trace Elements / Q000032:analysis*
C422271:2-(2-benzothiazolylazo)-p-cresol; D052160:Benzothiazoles; D003408:Cresols; D007202:Indicators and Reagents; D013844:Thiazoles; D014131:Trace Elements; D008982:Molybdenum