Development of Cellulosic Paper-Based Test Strips for Mercury(II) Determination in Aqueous Solution

Titration method (dropping-on method) was introduced as an efficient approach for determining the mercury ion (Hg²⁺) concentration in aqueous solution by using fabricated cellulosic paper-based test strips. In this study, dithizone used as a recognition reagent was physically loaded on cellulosic paper-based test strips for Hg²⁺ selective recognition. The sensing mechanism was established on the spectral absorption rate of the coordination compound that was formed by dithizone and Hg²⁺ under strong acidic conditions. The calibration curve was obtained by the absorbency of Hg²⁺-dithizone complexes from different Hg²⁺ concentration solutions, and the correlation coefficient (R ²) reached 0.9971. The detection range of the test trip for Hg²⁺ was obtained at 0.1 μg/mL to 30 μg/mL. Moreover, these superior cellulosic paper-based test strips have a rapid color-forming time (1.5 min) and low volume demand (3.7 μL samples at 0.0127 g/L dithizone recognition concentration). This portable paper-based test strip can give potential applications for field screening or on-site semiquantitative analysis.