3.5. Analytical performance
The performance of the developed method was evaluated for
the quantitative detection of Cu2+. Under the optimized conditions,
the color intensity values of modified AuNPls at the detection zone
on paper-based devices were examined at room temperature in the
presence of Cu2+ in the range of 0–350 ngmL1. The pinkest of the
violet colors at the test zone changed to colorless after adding Cu2+
to over 0.1 ngmL1, and these results can easily be distinguished by
the naked eye as shown in Fig. 6a. The plots of the mean intensity
and concentration of Cu2+ show a reasonable linearity in the range
of 0.5–200 ngmL1 (R2 = 0.9974), with a LOD and LOQ of 0.35 and