2.2. Reagents and solutions
All reagents were of analytical grade and were used
without further puri®cation unless otherwise stated.
Doubly distilled water was used for preparing the
solution. A 1000 mg l
ÿ1 stock manganese solution
(atomic absorption standard, Merck) was diluted as
required. A 0.05 M acetic acid adjusted to the desired
pH using ammonium hydroxide served as supporting
electrolyte and as the complexing agent at the same
time.
2.3. Procedure
The supporting electrolyte solution (10 ml) was
pipetted into the cell and deareated with nitrogen
for 10 min. The preconcentration potential
(850 mV, pH 9.0 and 1200 mV, pH 4.0) was
applied to a newly polished surface of the GCe while
the solution was stirred. Following the preconcentration
step, the stirring was stopped and after a certain
rest time ± indicated in the text ± the voltammogram
was recorded by applying a negative going scan, with
the parameters cited in Table 1 in the text, in case of
the cathodic stripping voltammetry (CSV) and applying
a positive going scan in the anodic stripping
voltammetry (ASV) experiments.