Sensitive and simple multi-ion detection using organic nanocrystal enrichment in paper analytical devices

Microfluidic paper analytical devices (& mu;PADs) are among the most promising platforms for heavy metal ion analysis. On the other hand, achieving simple and highly sensitive analysis of & mu;PADs is challenging. In this study, we developed a simple enrichment method for sensitive multi-ion detection utilizing water-insoluble organic nanocrystals accumulated on & mu;PAD. By combining the enrichment method with multivariate data analysis, three metal ion concentrations in the ion mixtures were simultaneously quantified with high sensitivity owing to the sensitive responses of the organic nanocrystals. In this work, we successfully quantified Zn2+, Cu2+, and Ni2+ at 20 ng L-1 in the mixed ion solution using only two dye indicators with a larger sensitivity improvement than those reported in previous studies. Interference studies revealed possibilities for a practical application in real sample analysis. This developed approach also can be used for other analytes.

Automated summary

In this study, a simple enrichment method utilizing water-insoluble organic nanocrystals accumulated on μPAD was developed for sensitive multi-ion detection. By combining the enrichment method with multivariate data analysis, three metal ion concentrations in the ion mixtures were simultaneously quantified with high sensitivity. Zn2+, Cu2+, and Ni2+ were successfully quantified at 20 ng L-1 in the mixed ion solution using only two dye indicators, with a larger sensitivity improvement than previous studies. Interference studies revealed possibilities for practical application in real sample analysis. This developed approach can also be used for other analytes.