Paper-based colorimetric array test strip for selective and semiquantitative multi-ion analysis: simultaneous detection of Hg²⁺, Ag⁺, and Cu²⁺.

A novel approach is presented in this article to qualitatively and semiquantitatively analyze multiple heavy metal ions simultaneously by a colorimetric array test strip. As a proof-of-concept application, a multi-ion analysis array test strip (for Hg(2+), Ag(+), and Cu(2+)) was fabricated through immobilizing five specifically responsive indicators in typical matrixes with tunable sensitivities. The as-obtained test strip shows not only high selectivity for Hg(2+), Ag(+), and Cu(2+), respectively, but also can be applied for their mixtures. The detection limit of the test strip is well below the Chinese wastewater discharge standard concentrations. Moreover, the array test strip demonstrates excellent anti-interference capability, detection, and production reproducibility, long-term storage stability, and real water sample applicability.