Dye Nanoparticle-Coated Test Strips for Detection of ppb-Level Ions in Water

Governments throughout the world are continuing to tighten contamination concentration limits and guidelines of harmful inorganic substances for industry and environmental water. For example, the World Health Organization recommends the standard allowance for water quality to be < 50. ppb for cadmium, lead, chromium(VI), mercury, selenium, and arsenic. Despite the increasing demands for simple and rapid monitoring of water quality, particularly for harmful ions, the sensitivities of commercial test kits and other existing methods are insufficient to meet the concentration guidelines.We have proposed next-generation simple methods for water analysis with high sensitivity to trace ions at ppb levels, named "dye nanoparticle-coated test strip" (DNTS). The DNTS is loaded with a thin layer (400. nm-2. μm) of indicator dye nanoparticles on the top surface of a membrane filter, providing a remarkably concentrated color signal. Therefore, almost all signals can be available, but in contrast to conventional test paper that dyes are distributed over the entire support. The DNTS is applicable not only to dip test but also to filtration enrichment in which target metal ions are concentrated by passing sample solutions through it. In addition, preparative procedures of DNTSs are simple and versatile based on the simple filtration of nano-dispersion of indicator dyes.