2.3. Measurement procedure
The bare glassy carbon electrode was polished to a mirror using
0.30 m and 0.05 m Al2O3 powder, respectively, and rinsed thoroughly
with doubly distilled water between each polishing step.
Then it was washed successively with doubly distilled water, 1:1
(v/v) HNO3 aqueous solution and doubly distilled water in an ultrasonic
bath and dried in air, and used for the following experiments.
An aliquot of the analyzed sample was pipetted into a 10.0 mL
calibrated flask and the solution was diluted to 2.2 mL with doubly
distilled water. Then, 0.2 mL of 100 mg L−1 Sb3+ and 0.5 mL of
100 mg L−1 Bi3+ were added. Subsequently, an appropriate concentration
of hydrochloric acid solution was added to the calibrated
flask. If the pH of the solution was different from 2.0 ± 0.1, NaOH or
HCl was added to obtain the required value. After that, the mixture
was added into the electrochemical cell for stripping voltammetric
measurement. The preconcentration was carried out at −1.30V
for 210 s under stirring and after a 15 s equilibration period, the
voltammogram was recorded by applying a positive-going SWASV
potential scan from −1.20 to 0.20V with a frequency of 25.0 Hz,
pulse amplitude of 50.0 mV and scan increment of 4.0 mV. Prior to
the next measurement, a 30 s clean step at 0.30V under stirring was
used to remove the residual metals from the Bi–Sb film.