2.3. ASV measurement
Generally, ASV measurement consists of three steps. Metal
ions firstly accumulate on the electrodes at a deposition potential
more negative to the equilibrium potential. Then differential pulse
voltammetry step was employed to dissolve the metal deposited
on the working electrode back into the analyte solutions. Finally,
working electrode should be cleaned to remove the residual metals.
Herein, heavy metal ions detection process was conducted on
a potentiostat using standard Ag+ and Cu2+ analyte solutions. Negative
potential (−0.4 V for Cu2+ and
−0.1 V for Ag+) was applied
on the working electrode for 3 min to accumulate the corresponding
metals on the diamond/graphite films. The reason for choosing
these parameters (deposition potential and deposition time) in
Cu2+ and Ag+ detection will be discussed in Section 3.4.1. Pulse
amplitude and pulse width applied here were 50 mV and 50 ms,
respectively and the increment potential of each step was kept
at 2 mV. Afterwards, working electrode should be cleaned at an
anodic potential of 0.4 V for 3 min to remove the residual metal.
Notably, prolonged cleaning time should be employed especially
when ion concentration in the analyte solution is relatively high