diamond/graphite electrode as shown in Fig. 6(e), showing a potential
rapid measurement ability in the detection of multi-metal ions.
According to the World Health Organization (WHO) guidelines for
drinking-water quality (2011), the guideline value for copper ion
is 2 ppm, while the health-based guideline value for silver ion is
unavailable since silver ion could be effective in maintaining the
bacteriological quality of drinking-water. But over-intake of silver
ion can cause argyria, thus the detection of trace silver ion is also
necessary. The lowest detecting concentration (5.6 ppb) for Cu2+
on the hybrid diamond/graphite electrode met the WHO standard
and the detection limit (5.8 ppb) for Ag+ can also be practical in
monitoring the quality of drinking water.