The water samples (pond tap water) were collected and filtered
through 0.45 lmcellulose acetate filter to remove some suspended
particles and preserved in an acid solution (HNO3). Then, known
amounts of 4 target metal ions were spiked into water samples.
The color of spiked water samples were developed under the
optimum conditions as described in quantitative determination
of metal ions. The semi-quantitative results of naked-eye detection
were compared with the actual metal ions concentrations determined
by ICP. The results in Table 4 show that the actual concentrations
of metal ions are close to naked-eye measurement and are
in the concentration range of the naked-eye detection. Thus, this
method can be applied to determine Cu(II), Pb(II), Fe(III) and Al(III)
in real water samples without any interfering effect.
Moreover, the pond water sample was divided into 30 samples
containing different concentrations of 4 metal ions, in the case of
both single and mixed metal ions. The metal ion concentrations
in each water sample were then determined by naked-eye and